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VENTILATION, WEATHER AND
THE COMMON COLD

A Study of the Prevalence of Respiratory

Affections Among School Children and

Their Association with School Ventilation

and the Seasonal Changes in Weather

GEORGE T. PALMER, M.S., Epidemiologist,
Detroit Department of Health

Reprint from

THE JOURNAL OF LABORATORY
AND CLINICAL MEDICINE

St. Louis

Vol. VI, Nos. 11 and 12, Vol. VII, No. 1, August,
September, and October, 1921

VENTILATION, WEATHER, AND THE COMMON COLD*

A STUDY OF THE PREVALENCE OF RESPIRATORY AFFECTIONS AMONG SCHOOL

CHILDREN AND THEIR ASSOCIATION WITH SCHOOL VENTILATION

AND THE SEASONAL CHANGES IN WEATHER

BY GEORGE T. PALMER, M.S., EPIDEMIOLOGIST
DETROIT DEPARTMENT OF HEALTH

INTRODUCTORY

DURING the last twenty years there has been a great amount of experimental
work on ventilation and its effect on the body. Workers in Europe and
the United States are in substantial agreement that it is the thermal factors
temperature, air motion and humidity which exercise the greatest influence
on human comfort, health and efficiency. The chemical composition of the
air we ordinarily breathe leaving out of consideration for the moment those
special industrial problems involving gases, fumes and dusts is of relatively
little moment in its effect on human conduct. School children are far better
off in a cool, airy room, regardless of the carbon dioxide content of the air,
than they are in air virgin pure chemically which is overheated.

It is most important that the facts as we have stated them should be
clearly understood, for otherwise, there is bound to arise, as there has in
the past, a misunderstanding as to the suitability of different methods of
ventilating school buildings.

If variable, as opposed to uniform, temperature, air motion and humidity
are desirable factors, then very satisfactory conditions can be maintained in
school rooms by ventilating with the windows, protected by deflectors, and
an exhaust duct on the opposite side of the room, heating being by direct
radiation beneath the windows. This method of ventilating will not always
give good aeration. At times the room will be amply flushed with outside
air. At other times, due to shifting winds, the circulation will be lessened,
the room will not be thoroughly flushed, and the carbon dioxide content
will rise, indicating an accumulation of the products of exhalation and body
vaporization. Even though the aeration of the room fluctuates, it is possible
to have coolness at all times and variability, and if the room is cool and

*This is an abridged form of a dissertation presented in partial fulfillment of the requirements for
the degree of Doctor of Public Health at the University of Michigan, 1920. >

This study was conducted jointly by the Bureau of Child Hygiene of the New York City Depart-
ment of Health, represented by Dr. S. Josephine Baker, Chief of the Bureau, and "the New York State
Commission on Ventilation, represented by the author, who then held the position of chief of the in-
vestigating staff. The collection of sickness records and the taking of temperature and other observations
on air conditions was done by nurses and physicians of the Health Department under the supervision of
Drs. L. Marcus and R. H. Willis. The routine clerical work of tabulation was likewise conducted by the
Health Department under the immediate direction of Dr. Franklin Van Wart. The planning of the
investigation, selection of schools, initial instruction of the field staff and the final analysis and interpreta-
tion of results is largely the work of the author.

507568
3

variable ,wMriii':(>e?taiii.limits.i"t makes little practical difference as to the
humidity.

On the other hand, if the experimental data of the last two decades are
wrong in minimizing the relative value of chemical purity of the atmosphere,
then window ventilation as we have described it is inadequate, and it will be
necessary to insure at all times voluminous and continuous flushing of the
room with outside air. This can be done only by mechanical means, that is
by plenum fans or blowers.

There has existed for some time a controversy as to the relative merits of
natural and mechanical ventilation. An inheritance from the days of Pet-
tenkofer, when chemical purity was regarded as vital, has kept alive the
carbon dioxide content as the standard of ventilation goodness. This
standard persists to this day. Measured in these terms the window venti-
lated room falls into disrepute. A carbon dioxide standard of 6 to 10 parts
per 10,000 automatically throws any form of window ventilation into the dis-
card. It is only by mechanical means that this degree of chemical purity
can be at all times assured.

With the development of mechanical ventilation there has grown up an
impression that uniformity in temperature, in air motion and in humidity is
ideal, and again the mechanically forced ventilation far excells the gravity
method in this respect. Furthermore the dust in outside air can be removed
readily under the mechanical system by the introduction of air washers. This
is not possible with window ventilation.

There is much then that can be accomplished with the plenum system that
is not possible under the window method. The question arises as to whether
the superiority of the mechanical system is superficial, a matter of a relatively
unimportant refinement so far as the school classroom is concerned. The
drawbacks to the mechanically ventilated classroom are its tendency to over-
heating, its unstimulating uniformity and its greater expense.

There is much to be said on both sides. The advocates of window ventila-
tion are impressed by its success with tuberculously inclined and undernour-
ished children. It has a wide application in our public schools at the present
time. If good for sick children, why not for well children? Is window ven-
tilation in the schoolroom to be ruled out of consideration merely because it
fails to live up to the carbon dioxide standard? It was for the purpose of
testing out these principles on a practical scale that the present experiment
was undertaken. After all, the proof of the pudding is "hi the eating. If
the health of school children, as measured by the amount of respiratory illness,
such as colds, tonsillitis, etc., is better under the more elaborate systems
of mechanical ventilation, then let us proceed to equip our buildings in this
manner. If, on the other hand, the mechanical ventilating equipment does not
supply substantial benefits to the health, comfort or efficiency of our school
child population, or is actually inferior in the things that count for health, let
us face the matter squarely.

There are innumerable demands for public funds. If we are paying out
vast sums of money for benefits which are not real but imaginary, recognition

of this fact cannot come too soon. If window ventilation provides the im-
portant essentials of a healthy atmosphere in a way that cannot be attained
or improved upon by mechanical systems of indirect ventilation, then our
school buildings should be built accordingly, and we should not hesitate because
a worn out standard of ventilation dictates otherwise.

During the latter part of 1916, from February 14th to April 6th (8 weeks),
and the winter of 1916-17, from October 30 to January 26 (12 weeks), observa-
tions were made on the health of 5500 New York City school children who
were exposed to various types of ventilation in 12 different school buildings.
In general these ventilation systems may be classified under three main
headings, as follows:

A Cold, open window rooms, gravity exhaust.

B Cool, window ventilated rooms, gravity exhaust.

C Plenum, fan ventilated rooms with gravity exhaust and with windows
closed.

As an index of health, the sickness records of the pupils w^ere used. The
condition of the air was determined by readings of temperature and humidity
and by the personal sensations of the observers as to temperature, moisture, air
motion and odor. It would have been desirable to determine also the carbon
dioxide content of the air, but this involved analytical work which the staff
was unable to do. The absence of these latter data was not serious, however,
for the Ventilation Commission had available a mass of data on this subject
collected over two years' time, and it was well established that the carbon
dioxide content of fan ventilated rooms averages several parts lower than in
window ventilated rooms.

For the convenience of the reader we shall reserve the description of work-
ing methods and ventilation types in individual schools for the later pages
and shall proceed with an account of the findings of this study.

RESULTS OF SICKNESS SURVEY IN DIFFERENT TYPES OF VENTILATED SCHOOL ROOMS

The first half of the study in the spring of 1916 covered 2500 pupils in
58 classrooms distributed among 8 schools. The second half in the winter of
1916-17 was represented by 3000 pupils in 76 classrooms in 12 schools.

In both studies the absences due to respiratory illness and the respiratory
illness among pupils present in school was greatest in the fan ventilated rooms,
Type C. This is the result after combining all records and disregarding in
this instance the balancing of the type of pupil, location of school, etc., which
will be treated more at length later on.

The excess of respiratory illness in the Type C rooms holds good both
for absentees and those in school. The total illness is least in the second
group, or cool, window ventilated rooms. The difference, however, between
the first and second types of window ventilation is less than between either the
first or second and the third. In other words, assuming for the moment that
these differences are due to atmospheric influences, the air conditions in the
first two types do not produce greatly divergent effects, but the influences at
work in the third type are distinctly less favorable.

The significance of these two sets of results may be expressed in this man-
ner; for every 100 cases of respiratory illness in the cool window ventilated
rooms, there are 152 in cold, window ventilated rooms; and 231 in fan venti-
lated rooms.

TABLE I

RESPIRATORY ILLNESS PER 1000 REGISTRATION
(PUPIL-SESSION) UNITS*

Ventilation
Type

FIRST STUDY

Among Among
Absentees- Pupils

Total

SECOND STUDY

Among Among Total
Absentees Pupils

in School

A-Cold,

Window

Rooms

10.6

37.2

47.8

9.2

75.3

84.5

B-Cool,

Window

Rooms

10.2

22.1

32.3

10.7

44.1

54.8

C-Fan

Ventilated

14.2

76.0

90.2

13.0

98.4

111.4

TABLE II
BASIC FIGURES FROM WHICH RATES IN TABLE I ARE COMPUTED

FIRST STUDY

.8"

SECOND STUDY

-g

.g.s

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61,658

655

2,298

89,067

822

6,705

71,231

728

1,578

113,959

1,218

4,661

65,088

925

4,950

115,215

1,497

11,329

The actual temperature conditions found in the three types of rooms are
disclosed in the two tables following, in one of which results are expressed as
averages, and in the other by temperature groups.

TABLE III
AVERAGE OF ROOM TEMPERATURES

Ventilation
Type

First Study

Second Study

Mean

58.8

59.1

59.0

66.9

65.9

66.4

68.8

67.9

68.4

*The unit of illness was one pupil per half-day school session. Illness is reported in pupil session
units. One pupil ill ten sessions counted the same as ten pupils ill one session. A pupil was continued
on the register regardless of the length of absence from school unless it was found that the family had
moved away from the school district, or that the pupil had left school permanently.

Separate tabulations have been made of illness resulting in absence from school and illness among
pupils who continued to attend school. The absences are classified as (1) absence from respiratory illness,
including coryza, bronchitis, pharyngitis, laryngitis, tonsillitis, pneumonia, tuberculosis and a miscellaneous
group variously termed grippe, colds, sore throat, etc.; (2) absence from illness other than respiratory,
namely: stomachache, backache, broken leg, etc. In this group were also the acute infectious diseases
such as diphtheria, measles, scarlet fever, whooping cough, chickenpox, mumps, etc. This was done be-
cause it was felt that the spread of these infections was largely determined by specific susceptibility
rather than by atmospheric influences; (3) absence due to causes other than illness, such as staying
at home to mind the baby, going on a visit, shopping with parents, truancy, etc.

The fan ventilated or Type C rooms averaged but two degrees higher
than those of Type B and nearly ten degrees warmer than Type A. Type
A was extremely cold for a school room. Type B was cooler than is cus-
tomarily found. The average temperature of Type C, though higher than B,
was not exceptionally high.

There was a wide range in the daily temperatures, which are lost sight of in
the averages.

TABLE IV

FREQUENCY DISTRIBUTION OF TEMPERATURES
PER CENT OF SESSIONS

Types
Ventilation

59 and below

60-69 .

70 and over

1st Study

2nd Study

0.2

0.8

The A rooms rarely reached 70. Fully half of the sessions were below
59. The B and C rooms rarely fell below 60. The temperatures in the
second study were much more uniform, particularly as regards Type C and to
a lesser extent Type B. More than one-third of the sessions in B and C in the
first study were above 70. Much of this represented an overheated condition.
However, the first study was made in the late winter, when greater outdoor
variation is experienced than from November to January. Although the pro-
portion of sessions between 60 and 70 does not appear to differ much in the
B and C rooms, yet there was an appreciable difference within this range.
Thus, in the first study 24 per cent of sessions in B were from 60 to 64,
whereas but 6 per cent of the sessions in C were within this range. Thirty-
seven per cent of B sessions were from 65 to 69 as against 51 per cent of the
C sessions. The C rooms were warmer, as the averages have already indicated.

The interesting point to be noted is that whereas there was but two de-
grees difference in temperature between the B and C rooms, there was a wide
difference in the sickness rates. Between 7 and 8 degrees separated Types A
and B, and yet in spite of this the sickness rates were quite similar. Evi-
dently some factor other than temperature operated differently on these three
classes of rooms or else a rise of two degrees above 66 is far more conducive to
colds than a drop of as much as 7 degrees.

HUMIDITY

The relative humidity ranged from 38 to 46% and did not differ greatly in
the three classes.

As would be expected, the relative humidity was higher in the colder
rooms. With the same amount of moisture present as in Type A, the relative
humidity in the first study at the temperature in Type B would be 33.4,

RELATIVE HUMIDITY

Ventilation First Study Second Study
Type

A 43,7 46.3

B 37.8 43.0

C 37.8 41.2

and in Type C 31.4. The corresponding figures in the second study would
be 29.9 for B and 28.7 for C. It would appear, therefore, that there was an
accumulation of moisture in the Type B rooms, and this could only come
from reduced aeration. In Type C the same explanation would hold. The
rooms at P. S. 59 were humidified, as were also the rooms at P. S. 51 and 97,
but this would hardly affect the average of all rooms in the group to this
extent. It is also possible that the taking of the humidity reading was not
as accurately done in the dry rooms, the wet bulb being read before the mer-
cury column had completed its fall. These readings are higher than we should
expect at this season of the year, judging from records taken by the Com-
mission in similar rooms in other schools.

Other indices of air conditions were the opinions of the nurses who visited
the rooms at least twice daily.

FRESHNESS AND ODOR

The results of the nurses' votes on the freshness or lack of freshness and
presence of odor in the rooms are given in Table VI.

TABLE VI

PERCENTAGE OF SESSIONS JUDGED

Ventilation Exceptionally Odor Absent but
Type Fresh not Exceptionally
fresh

Odorous

First Study
A 62
B 25
C 21
Second Study
A 69
B 18
C 22

24
57
64

28
62
67

14
18
15

3.2
20
11

The results are very interesting from several points of~view. The Type
B rooms are most odorous in both studies. The excess over the others was
slight in the first study, 18, as compared to 15 for Type C and 14 for A. It
was more marked in the second study, 20, as against 11 for C and only 3.2
for A.

The freshest rooms are the coldest rooms. Sixty-two per cent of the
sessions in Type A in the first study were judged exceptionally fresh, and
in the second study the figure was 69 per cent. The figures for Type B were
25 per cent in the first and 18 in the second. Type C had 21 per cent in the first
and 22 per cent in the second.

What seems clear from these figures is that to be exceptionally fresh the
greater part of the time, rooms must be well below 65 degrees in temperature.
Warmer rooms may be free from odor and yet exceptionally fresh not much
over one-fifth of the time.

In rooms that did not differ greatly in temperature, as B and C, the
greater aeration produced by fan ventilation reduced odor to a slight degree
in the first study, and to a marked degree in the second. It failed to make
the rooms any fresher in the first study, but did help out in the second study.

Although we do not possess complete records of the carbon dioxide con-
tent, there is little doubt but that the smallest amount would be found in the
fan ventilated rooms, Type C, as we have already pointed out. Repeated
records collected in three schools show this tendency (Table VII).

TABLE VII
CARBON DIOXIDE IN PARTS PER 10,000

SCHOOL

VENTILATION TYPE

B C

33
115

6.9 5.5
7.6 6.5'
8.6 5.7

The markedly greater freshness of the Type A rooms is due, without ques-
tion, to their low temperature, and not because of the greater chemical purity
of the air. Freshness is not a question of odor, for the Type B rooms were
fresher than C and yet more odorous.

SENSATION OF TEMPERATURE

The recorded votes of the nurses as to whether the temperature of the
rooms felt "too cool," "satisfactory" or "too warm" are given in Table VIII.

TABLE VIII

VENTILATION
TYPE

PER CENT OF SESSIONS JUDGED
TOO COOL SATISFACTORY

TOO WARM

First Study

7.9

6.2

Second Study

3.9

8.6

3.6

In the first study the per cent of satisfactory sessions was about the same
in all three types, being in the neighborhood of 77 per cent. There were more
sessions judged "too warm" in Types A and B than in C, although the average
temperature was lower than C. The "too cool" sessions were most numerous in
Type C, the rooms of highest temperature. In other words, the coldest rooms
felt warmer than the warm rooms. In view of the actual temperature found, it
would appear that the nurses were influenced in their judgment of what the

temperature should have been rather than by actual sensation. In no other
way can we account for the votes in rooms whose temperature differed by at least
ten degrees, as was the case in Types A and C.

The votes in the second study more nearly reveal the actual temperature
condition as indicated by the thermometer. In A 26 per cent of the sessions
were judged "too cool." In fact, 4 per cent were voted "too cold" an ex-
treme condition. In Type B, 8.6 per cent were "too cool" and in C 3.6
per cent.

Type C had the greatest number of sessions judged satisfactory as to tem-
perature; namely, 85 per cent. The corresponding figure for Type B was 80
and for A, 70.

Too great warmth was experienced 12 per cent of the time in C, 11 per cent
in B and but 3.9 per cent in A.

The sensation of temperature reflects the actual thermometer reading to
some extent at least. There was much lesss overheating in the second study,
and this agrees with the lesser number of "too warm" votes.

SENSATION OF MOISTURE

As will be seen from the figures given below, over 80 per cent of sessions
in all three types of the first study were judged satisfactory as to moisture.
Both moisture and dryness were most pronounced in Type C.

TABLE IX

VENTILATION
TYPE

PER CENT OF SESSIONS JUDGED
MOIST SATISFACTORY

DRY

First Study

5.9

6.7

1.7

9.0

7.3

9.7

Second Study

0.6

6.4

8.5

7.9

The second study reveals a greater divergence between the rooms. Type
C had the highest percentage of satisfactory sessions, 84. Type B had but 74
per cent and Type A, only 66. The cooler sessions are associated with moisture,
the warmer sessions with dryness. " One-third of all sessions in A were
moist and less than 1 per cent dry. Twenty per cent of sessions in B were
moist and 6.4 per cent dry. Eight and five-tenths per cent of C were moist
and 7.9 per cent dry.

There was less overheating in the second study and the sensation of
dryness is less. Type C is similar in both studies. The other two types are
different in that the second study shows many more moist sessions.

AIR MOTION

The greatest proportion of satisfactory votes as to air motion was found in
A. Moving air was noticed most frequently in A and least in B. The results

of both studies are similar, although it is surprising to find the sessions in
Type C judged "dead" to be more numerous in the second study where the
air flow through the rooms was greater and the temperature was lower.

TABLE X
PER CENT OF SESSIONS JUDGED

VENTILATION
TYPE

DEAD SATISFACTORY

BREEZY

First Study

4.7

7.1

9.3

Second Study

9.2

7.0

9.8

ANALYSIS OF SICKNESS RATES IN INDIVIDUAL ROOMS AND SCHOOLS

A S we have pointed out in the introductory remarks, great care must be
** taken in drawing conclusions as to the correlation of different facts from
the average results of a group. In the study before us it will be necessary to
inquire into the records of each school and of the individual rooms to see
whether they agree uniformly with the characteristics of the group.

In Tables XI and XII are assembled records for each room covering the
nature of air conditions and the amotint of respiratory sickness.

It is noticeable that there is a wide variation in respiratory illness. Room
415 (Type B) at P. S. 22 in the second study had no absences whatever from
respiratory illness. Room 311 (Type C), P. S. 115, in the second study, has a
rate of 50.4. These represent the minimum and maximum limits. The range
of respiratory sickness-in-attendance rates is even greater from zero to 316.

Room 311, P. S. 59 (Type A) is the most congested in the first study,
there being but 6.5 square feet of floor space per pupil. In spite of this
crowded condition, the absence rate from respiratory disease is only 0.6 one
of the lowest. On the other hand, Room 202, P. S. 165, being the least con-
gested, with 19.6 square feet per pupil, has a respiratory absence rate of 37.0,
a very high figure. Overcrowding does not inevitably lead to respiratory
illness.

The average temperature of Type A rooms was about 59 degrees in both
studies. This is much colder than the ordinary school room. In fact, it
seems from our general experience entirely too cold for public school children,
and yet, on looking over the absence rates, there is no indication that these
children had more colds as a result. In fact, the average absence rate for the
entire group is lower than the other two ventilation types, as has already
been pointed out. In the first study there are only two rooms in Type A with
rates over 20. There are three each in Types B and C. Respiratory sickness
among those present in school is greater in Type A than in B, but less in A
than in C.

In spite of the well intentioned efforts to balance the three types of rooms
in the matter of schools and type of pupil, this could not be carried out to

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CO rH CO CO

I-H cq cq

qj CO Oi <* rH rH

oo Cq CO CO rH rH

rH 00 Oi rH Oi
rH Cq rH CO i 1

b- b- CO Oi 00
rH CO

CO O rtf rH
rH

, s

i'i

m o co cq cq

rH rH CO CO CO

CO CO b- O CO b-

rH r}H rH CO CO Cq

rS 10 rH Cq CO
I CO Cq cq rH rH

CO OO b- Oi O

00 CO CO
IO IO CO CO CO

rH rH b-

co cq cq cq

. g

5 w

cq co oo b- co

OO 00 rH rJH b- 00

^ 10 Cq rH rH

IO IO Oi 00 00

CO O rH O IO

cq cq oo *o

o cq' rH 10 10"

CO CO CO CO CO

CD Cq CO Oi b- rH

CO CO CO CO CO b-

K> Oi oo* oi oo' t^

S3 CO CO CO CO CO

GO 00 00 b- b-

CO CO CD CO CO

oo oo co oo b-

CO CO CO CO CO

o* cq* o* o*

b- b- b- t

CO rji 10 rH

CO rH CO b- CO O>

to Cq 10 rH 10

CO Oi Oi 00 rH

CO Oi Cq rH

co oo cq co

w g

rH rH CO rH CO

r}< rH rH r-l CO CO
rH CO CO rH b-

e b^ CO O* rH Cq*
S b- CO CO rH (M

rH rH CO CO CO
CO CO 10 b-

rH Oi rH rH rH

o o 10 b- co

b- 00 rH 10
CO TH Oi rji

i |

Cq rH rH rH

rH rH

02 g
H fc*

CO Oi CO CO

rH Cq Oi CO Oi IO

cq b- cq TH o

CO CO OO IO IO

CO CO O CO

02 O

rH
CO Oi rH

rH i-H CO rH b- b-

. cq cq co rH

< rH* Cq t>* rH* cq'
gg CO CO rH rH

IO* 00 Oi O CO
Cq 00 rH r^ CD
rH rH rH rH

CO b- IO Cq rH
Oi Oi rH b* Cq

CO* i-H CO CO*

co oo o co

>H << EH sj

^ g

jTl .EH

rfl rH Oi IO

Cq Cq rH rJH b- rH

O OO CO O O

Oi Oi Oi OO rf

CO rH 10 CO

o o cq o

rH rH O O rH
CJ r-l rH

CO 10 CO
rH rH rH Cq

CO CO b- O

00 CO b- CO O

00 Cq 00 rH Oi

rH t-" o" cq

CQ CTJ CTJ

JO CO OO rH CO
rH rH rH
CO ^H CO ^i ^

10 co oo cq co Oi
o o o o o o

CO rH rH CO CO CO

b- b- o cq co

Cq CO CO rH rH

rH rH rH >O rH
00000
rH CO rH rH IO

CO 10 r^ 10
O O rH O O

10 10 cq co co

rH Cq 00

o o cq o
cq cq cq co

Oi Oi
CO IO

CO IO

b- co

.J cq
&

Oi
IO

TABLE XII
RECORDS OF INDIVIDUAL ROOMS IN SECOND STUDY

RESPIRATORY SICKNESS RATES
02 |

ft*
1

AV. REL.
HUMIDITY

PER CENT
W

5 Q

PH O

W Q 03

H 00.

Type A Cold Open Window

Eooms

303

3.9

46.6

50.7

59.9

58.0

2 A

409

8.1

13.7

21.8

61.3

54.4

4 B

410

11.1

14.2

25.3

60.3

56.0

4 B

202

6.9

65.0

71.9

58.7

41.3

3 A

203

40.0

53.0

56.2

43.4

4 A

204

21.6

45.9

67.5

56.6

43.1

3 B

205

6.7

30.3

37.0

58.7

42.2

3 B

206

9.3

24.9

34.2

58.3

40.3

3 A

207

11.7

18.4

30.1

57.6

41.4

4 B

308

4.0

165

169

60.0

48.0

100

3 B

311

8.5

144.

152.5

58.5

48.9

100

3 A

313

26.8

213

239.8

59.0

44.7

2 A

412

4.3

150

154.3

58.1

45.1

100

4 A

413

9.2

147

156.2

60.0

48.0

4 B

414

3.0

124

127

57.8

48.4

100

4 A

416

8.0

91.3

99.3

57.6

46.5

100

4 B

301

5.1

44.1

49.2

60.2

44.8

5 B

309

11.6

34.8

46.4

58.9

45.9

4 A

402

6.1

18.4

24.5

60.5

44.7

6 A

403

6.2

39.4

45.6

63.5

45.3

5 B

Type B-

-Moderate

Temperature, Open

Window

Eooms

2 Bx.

301

10.7

9.7

20.4

68.6

38.5

2 B

302

7.7

5.8

13.5

69.0

38.5

2 B

316

11.6

12.2

23.8

65.4

40.0

5 A

405

9.5

33.2

42.7

62.2

57.8

4 A

408

15.9

31.4

47.3

63.5

59.0

3 B

411

9.9

5.8

15.7

63.8

60.6

4 A

415

67.6

57.7

5 B

416

5.5

2.7

8.2

68.2

56.0

6 A

418

24.6

25.5

67.3

56.7

5 B

33 Bx.

21.4

55.7

77.1

69.3

31.3

8 B

27.5

47.5

75.0

69.4

37.2

7 A

302

10.9

33.6

44.5

63.0

40.3

4 A

308

8.6

42.8

51.4

65.0

37.7

5 A

408

2.9

58.0

1 60.9

65.2

39.0

5 A

318

3.7

187

190.7

64.9

48.5

3 A

415

16.2

158

174.2

58.8

48.2

100

4 B

305

9.7

32.7

61.6

46.5

4 B

406

2.7

43.7

67.1

43.3

3 A

408

61.1

43.6

74 '

3 B

302

6.4

67.0

38.2

5 B

313

7.1

67.3

41.8

4 A

501

3.0

65.9

44.8

6 B

115

312

23.3

67.8

28.8

4 B

502

40.2

67.9

26.2

5 B

TABLE XII (CONTINUED)

RESPIRATORY SICKNESS RATES
M

rn O

PER CENT

SESSIONS

jri

III

PH
1

o
o

|sE!

> ^

PH*
CO

<1 H <

< w

503

29.8

67.0

29.5

5 B

165

302

1.3

100.3

67.2

35.9

5 B

306

10.4

66.4

66.8

35.7

4 B

309

8.1

41.1

68.9

36.1

4 B

Type

C Moderate Temp.

, Fan

Ventilated,

Closed

Window

Rooms

2 Bx.

207

22.4

25.5

47.9

66.1

39.6

2 A

307

13.2

17.0

30.2

65.8

41.2

O -D

310

1.3

3.8

5.1

66.5

41.5

4 B

402

4.8

5.6

10.4

66.5

57.0

6 A

403

3.5

1.3

4.8

65.8

56.2

4 B

404

14.4

32.4

66.5

54.9

4 B

33 Bx.

29.3

52.3

71.0

28.6

6 B

45.4

125

170.4

70.2

32.0

5 A

51 Bx.

203 (Hum.

) 4.0

148

152

67.6

43.6

6 A

205

14.7

64.7

67.4

29.0

6 A

203

16.8

182

198.8

69.2

6 B

205

13.9

275

288.9

69.2

45.5

6 B

206

9.9

316

325.9

69.6

6 A

501

12.4

256

268.4

68.9

5 B.

503

9.1

197

206.1

69.2

47.9

5 B

505

8.3

112

120.3

68.7

49.3

6 A

303

2.3

34.1

36.4

68.0

43.1

4 B

308

2.7

34.7

37.4

68.3

40.2

5 A

502

6.8

43.3

50.1

66.3

44.8

6 B

115

308

24.8

68.8

27.2

4 A

311

50.4

51.6

102

68.2

25.2

4 B

147

210

16.6

11.9

28.5

68.1

42.4

3 A

304

3.6

6.8

10.4

67.7

40.4

4 B

305

4.2

12.4

16.6

67.1

5 A

165

201

11.9

196

207.9

68.4

33.3

4 A

202

5.3

151

156.3

68.0

34.5

3 B

220

181

191

69.2

4 A

308

1.8

154

155.8

68.7

5 B

the degree desired. If the pupils in one district are by reason of hereditary
and environmental influences more susceptible to colds, then this school will
unduly raise the sickness rate in the ventilation type within which the major-
ity of its records fall.

Of the 12 schools used in the two studies, only one possessed all three
examples of ventilation. In one other instance the three types were repre-
sented by two schools a block or so apart, one school having Type C and the
other, Types A and B. In all other instances there were not more than two
types represented within a school building, some buildings having A and B and
others, B and C. The division of rooms is revealed in the table below.

One can readily appreciate by looking at the table how the results would be
affected if, say, School 39 were given to very little sickness and School 147 to

TABLE XIII
DISTRIBUTION OF TEST BOOMS AMONG THE TWELVE SCHOOLS BY VENTILATION TYPE

FIRST STUDY

SECONb STUDY

SCHOOL

147

165

2 Bx.

33 Bx.

51 Bx.

115

Total

a great deal. In the summary of all rooms Type A, having 6 rooms in School
39 would have a low sickness rate, not because of ventilation, but because of
its personnel, and Type C would be inclined to have a high rate, not because
of ventilation but because of the numbers of children from School 147. Theo-
retically this influence should have been eliminated at the beginning, but
actually this was found impossible.

The total respiratory illness rate including both absentees and those
present in each school is shown in Table XIV.

TABLE XIV
TOTAL RESPIRATORY ILLNESS RATES BY SCHOOLS

SCHOOL

FIRST STUDY

SECOND STUDY

46.7

100.3

13.6

12 & 147

31.1

27.9

37.4

44.2

51 Bx.

106.4

103.1

193.3

12.6

51.6

2 Bx.

55.9

24.2

165

77.9

123.3

33 Bx.

92.6

A considerable variation is seen in the illness rates. Schools 59 and 165
are relatively high in both studies. Schools 12, 147 and 73 are low in both.
School 22 is high in the first study and extremely low in the second.

We may examine the effect of ventilation apart from these extraneous in-
fluences mentioned first by inspecting the records of each school by itself
and secondly by balancing the influence which each school exerts on the total.

In an effort to illustrate the comparison of illness rates within each school
we have prepared Charts I and II, the former showing Types A and B and
the latter, B and C. Both measures of illness among the absent and among
those present are included. The frequency with which one ventilation type
exceeds the other in amount of illness conveys an impression that is not brought
out in the averages for each ventilation type.

In the comparison of the window ventilated rooms from the chart, Type
B exceeds Type A in respiratory illness in nine instances. In the remaining
seven instances Type A exceeds Type B. There is then no prevailing superior-
ity of one type over another. It will be noted in the summary at the bottom
of the chart, where the rates have been averaged, that Type B shows less re-

COMPARISON OF RESPIRATORY ILLNESS RATES
IN VENTILATION TYPES A (Cold Open window Rooms)

AND B ( Moderate Temperature, Open Window Rooms)

Summary

Chart I.

spiratory illness than A. This is due to the influence of several high rates in
Type A. Incidentally this illustrates how an erroneous impression may be
gained from averages alone.

In the comparison between Types B and C, the latter exceeds the former
in respiratory illness in eighteen instances ; whereas B exceeds C in only seven

instances. This result is much more significant than in the previous comparison.
The averages of the rates are consistent with the tendency of the individual
instances. With the new schools used in the second study included, the
average for Type C exceeds B in both measures of respiratory illness. The
same is true with the new schools omitted.

COMPARISON OF RESPIRATORY ILLNESS RATES

IN VENTILATION TYPES B (Moderate Temperature
Open Window Rooms ) AND C (Moderate Temperature
Fair Ventilated Rooms)

SUMMARY

New Schools of 2nd Studv Included

Chart

This analysis confirms what has been brought out previously that the
difference between Types A and B is insignificant; whereas, between B and
C there is a distinct excess of illness in the fan ventilated rooms.

In School 59 all three types of ventilation are represented. We have in
this instance a good measure of ventilation influences on pupils of the same

general characteristics. The fan ventilated rooms have the greatest respira-
tory illness in both studies. The relative positions of A and B are not the same
in the two studies, the cold rooms having more illness in the first study and less
in the second.

TABLE XV
RESPIRATORY ILLNESS BATES IN THREE VENTILATION TYPES AT SCHOOL 59

VENTILATION
TYPE

FIRST STUDY

SECOND STUDY

SICKNESS
CAUSING

ABSENCE

SICKNESS
IN
SCHOOL

SUM

SICKNESS
CAUSING
ABSENCE

SICKNESS
IN
SCHOOL

SUM

A
B

4.6
9.1
13.7

53
139

94.6
62.1
152.7

9.0

10.2
11.7

148

172

223

157
182
235

The room temperature for each type -averaged as follows:

A 58.8 58.7

B 65.4 61.9

C 68.2 69.1

The fan ventilated rooms were the warmest, exceeding the Type B
rooms by 2.8 degrees in the first study and by 7.2 degrees in the second.
These results are consistent in showing less illness in the window ventilated
rooms.

In one other instance the three ventilation types are to be found divided
between two schools within a block of each other and for all practical pur-
poses the characteristics of the pupils are the same. The sickness rates for
Schools 12 and 147 are shown in Table XVI.

TABLE XVI
RESPIRATORY ILLNESS RATES IN THREE VENTILATION TYPES AT SCHOOLS 12 AND 147

VENTILATION
TYPE

FIRST STUDY

SECOND STUDY

SICKNESS
CAUSING
ABSENCE

SICKNESS
TN
SCHOOL

SUM

SICKNESS
CAUSING
ABSENCE

SICKNESS
IN
SCHOOL

SUM

A
B

9.3
7.0

6.5

8.6

15
47

17.9
22.0
53.5

7.7
-11.7

8.2

22
24
10

29.7
35.7

(Temperature 1st Study A 60.5, B 66.6, C 67.3; 2nd Study, A 60.5, B 63.2, C 67.6.)

The fan ventilated rooms appear to better advantage in this instance,
for illness is lowest in Type C in the second study. In the first study the total
illness is greatest in the fan ventilated rooms, although the illness causing
absence is the lowest of the three types.

The Type C rooms at School 59 were unusually well equipped with
mechanical ventilation facilities. The air is humidified before entering the
room, and the blowers are capably managed. The fan equipment at School
147 is older and the rooms were not thoroughly aerated at all times, and
windows were frequently found open.

In view of the oft repeated assertion that humidification and air washing
in combination with the plenum fan is from many standpoints a superior

form of ventilation, the figures of this study are of special interest. A
modern form of mechanical ventilation with warm temperature is associated
with more respiratory sickness than naturally ventilated rooms with gravity
exhaust. On the other hand, fan ventilation, lacking many modern features,
as in P. S. 147, is associated with less respiratory illness than naturally ven-
tilated rooms. At P. S. 147 the temperature of the fan rooms was lower than
at P. S. 59. Raising the temperature over 68 degrees would seem to be more
disturbing to health than reducing the volume of air passing through the
rooms.

The temperature of the A rooms in all instances was lower than those se-
lected as B rooms. In general the C rooms were warmer than B, although
there were some exceptions to this.

TABLE XVII

AVERAGE TEMPERATURE AND TOTAL BESPIRATORY ILLNESS RATES BY
VENTILATION TYPES IN EACH SCHOOL

SCHOOL

VENTILATION
TYPE

FIRST
TEMP.

STUDY
RATE

SECOND
TEMP.

STUDY
RATE

147

B
C

60.5

66.6
67.3

17.9
22.0
53.5

60.5
63.2
67.6

29.7
35.7
18.2

A
B

57.2
61.6

15.5
9.5

57.7
64.4

50.6
52.5

A
B
C

58.8
65.4
68.2

94.6
62.1
153

58.7
61.9
69.1

157
182
235

A
B

60.1
65.3

58.4
16.3

60.8
66.6

4] .2
47.1

2 Bx.

B
C

70.4
69.1

57.0
54.8

67.7
66.1

19.6
28.6

B
C

69.6
68.1

51.8

22.7

67.7
66.3

11.1
16.1

165

B
C

69.6
70.9

50.4
105

67.6
68.6

66.0
180

33 Bx.

B
C

69.4
70.6

76.2
109

115

{ t

67.6
67.6

30.4*
47.2*

66.7
67.6

52.6
40.7

*This

is absence illness only.

Whenever temperatures are over 68 degrees, the warmer rooms have the
greater sickness, regardless of whether Type B or C. When temperatures
are below 68, the window rooms have less sickness in four instances and
more sickness in two instances.

It may be pointed out in this connection that even where the temperatures
of a fan and window room, as measured at the three-foot level, are identical,
the window room is actually cooler, for the temperature at the floor level is al-
ways lower in the window rooms.

The second means of shedding light on the significance of the grand av-
erages is by equalizing the influence of each school in each ventilation group.
In doing this we have combined the two studies, omitting the schools that
were not represented in both. Where there are 9 rooms at a school, 6 in
Type A and 3 in Type B, we have reduced the number in the first type to three
by averaging the two highest readings, the two lowest and the two interme-
diate. Where there are four readings, we have averaged the two highest and
used the other two as they stand.*

We have illustrated in Tables XVIII and XIX the manner of making
this computation by showing the selected rates used along with the original
figures.

In Table XX will be found the averages of the rates both actual and ad-

TABLE XVIII

ACTUAL AND SELECTED RESPIRATORY ILLNESS RATES BY ROOMS
COMPARISON OF TYPES A AND B (BOTH STUDIES COMBINED)

ABSENCE RATE
TYPE A TYPE B
SCHOOL ACTUAL SELECTED ACTUAL SELECTED

ILLNESS IN ATTENDANCE RATE
TYPE A TYPE B
ACTUAL SELECTED ACTUAL SELECTED

12 15.

15.

4.5

10.

15.

8.6

11.3

14.

5.0

5.1

16.

17.

3.9

9.5

47.

33.

8.1

15.9

14.

31.

11.1

9.9

14.

39 11.

11.

6.9

11.

21.

14.

1.4

19.

6.9

6.8

10.9

65.

55.

34.

6.7

8.6

9.3

10.5

2.9

35.

43.

11.7

13.0

17.3

25.

21.

58.

21.6

18.

59 .6

15.1

210.

151.

61.

10.9

8.2

8.4

1.5

72.

47.

91.

8.5

21.

5.8

74.

15.

26.8

3.7

213.

9.2

18.

16.2

165

189.

187.

8.5

10.

124

8.3

108

158.

4.3

144

3.0

3.8

150.

147.

173.

147.

73 25.8

18.8

3.2

57.

11.5

10.2

34.

6.4

10.4

32.

24.

10.8

11.6

8.9

9.7

42.

23.

6.2

2.7

35.

41.

6.1

16.

18.

51.

5.1

*This might be done by averaging the two lowest or the two intermediate rates, letting the
highest value stand. The difference, however, is too slight to alter the final result.

TABLE XIX

ACTUAL AND SELECTED RESPIRATORY ILLNESS RATES BY ROOMS
COMPARISON OF TYPES B AND C (BOTH STUDIES COMBINED)

ABSENCE RATES ILLNESS IN ATTENDANCE RATES
TYPE B TYPE C TYPE B TYPE C
SCHOOL ACTUAL SELECTED ACTUAL SELECTED ACTUAL .SELECTED ACTUAL SELECTED

2 Ex. 3.1

3.1

13.

36.

64.

31.

38.

33.

16.4

13.3

47.

10.7

22.4

10.

26.

7.7

13.2

17.

11.6

1.3

12.

22 5.7

5.7

7.0

8.5

10.5

12.

8.0

8.9

25.

4.8

5.5

3.5

14.4

25.

18.

59 15.1

15.1

17.9

17.4

61.

188.

176

10.9

16.9

91.

163.

1.5

16.8

14.7

15.

149.

145.

12.6

140.

10.4

9.2

97.

8.0

97.

3.7

16.8

15.4

187.

316

296.

16.2

13.9

158.

275.

10.

12.4

11.2

173.

256.

227.

9.9

197.

9.1

8.7

182

147.

8.3

112.

12 & 4.5

4.5

8.4

15.

46.

147 11.3

11.3

1.5

14.

73.

5.1

9.6

17.

22.

9.5

16.6

33.

12.

15.9

3.6

31.

9.9

4.2

12.

165 10.4

10.4

37.0

36.1

21.

156.

119.

5.7

35.0

38.

82.

26.4

34.

48.

34.

12.

34.

1.3

11.9

11.

99.

196.

189.

10.4

10.

56.

181.

8.1

5.3

33.

154.

1.8

151.

justed. Where the school influence is thus equalized in each ventilation type
the average illness rates are appreciably different from the unconnected av-
erages. In the comparison of Types A and B only those schools have been
used which possessed both A and B rooms. A B room in a school not having

TABLE XX

COMPARATIVE RATES OF RESPIRATORY ILLNESS WITH UNCORRECTED AND BALANCED AVERAGES

(BOTH STUDIES COMBINED)

VENTILATION

ABSENCE RATE

ILLNESS IN ATTENDANCE RATE

TYPE

UNCORRECTED

BALANCED

UNCORRECTED

BALANCED

10.0

9.6

9.0

9.1

9.4

12.0

11.1

an A room is omitted. Similarly, in the comparisons of B and C rooms, B
rooms are omitted where there is lacking a C room in the same school.

Before correcting for number of rooms the absence rates for A and B were
10.0 and 9.0. After eliminating the abnormal influence of the schools with
the most rooms, the rates are 9.6 and 9.1. In the first instance Type A was
greater than B, largely because of the greater number of rooms at Schools
39 and 59, where the rates are higher.

The effect of eliminating the school influence is even more noticeable with
the rates for illness in attendance. Without correction the rate for A was
57 and for B, 39, an appreciable difference. When the influence of each
school has been equalized, the rates are 48 for A and 45 for B. In the former
instance A exceeds B only because it possessed more rooms at P. S. 59, where
the rates are high, and not because of any ventilation influence.

The corrected absence rates for Types B and C are 9.4 and 11.1, a differ-
ence of 1.7. Before the correction had been applied the rates were 9.4 and 12.0,
a difference of 2.6. It was the greater number of rooms at P. S. 59, where
the rates are high, that raised the average for Type C. When this influence
is modified the difference between the two types is less.

A marked alteration is also produced in the rates for illness-in-attendance.
Without the correction for number of rooms, the figure for B is 38 and for C,
94, a difference of 56. Eliminating the school influence the rates are 43
and 73, a difference of only 30. School 59 is largely to blame for the apparent
wide difference in the types. With an equal number of rooms at each school
we obtain a truer conception of the difference in ventilation types.

Having arrived at comparative figures which are believed to give a fairly
accurate measure of the ventilation influence, we are confronted with the
interpretation of these results. Is the difference of 0.5 between the absence
rate in A and B significant, or is it a chance result which, if the experiment
were repeated, would reverse itself? We can answer this question by deter-
mining the probable error of the averages. If the differences are statisti-
cally significant, they will represent at least three times the value of the prob-
able error. If the differences are no greater than the probable error, then
we cannot say that ventilation exercises an unmistakable effect on the health
of these school children.

The formula for the probable error is

P. E. 0.6745

The computation of the probable error is made by averaging the absence
rates in each type: finding the deviation of each rate from the average; squar-
ing each deviation; averaging these squares; determining the square root from
this average; dividing this figure by the square root of the number of cases,
which gives the standard deviation and finally multiplying this figure by the
constant, 0.6745, which gives the probable error, or P. E.

The difference in the absence rates between Types A and B, 0.5, is less
than the probable error, or approximately 0.7, and in consequence, is without
significance. This means that the evidence is insufficient to prove that either

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type of ventilation is superior to the other in so far as respiratory illness is
concerned.

Eespiratory illness of a less severe nature and sufficient to keep children
out of school is likewise, judging by the fact that the probable error exceeds
the difference in rates, no different in a cold, window ventilated room with a
temperature around 59 degrees than in a cool, window ventilated room whose
temperature is in the neighborhood of 64 degrees. This finding is in agree-
ment with the original computations for the entire group of rooms.

The differences between Types B and C are more marked. The higher
probable error for absence rates, that is for Type C, is 1.0. The difference

TABLE XXI

PROBABLE ERROR OF RESPIRATORY SICKNESS BATES
(BOTH STUDIES COMBINED)

DIFFERENCE BETWEEN

PROBABLE DIFFERENCE BETWEEN PROBABLE

VENTILATION TYPES

ERROR

VENTILATION TYPES ERROR

A AND B

B AND C

Absence
Eate

0.5

A
B

.69
.71

1.7 A .88
B 1.00

Sickness in
Attendance
Eate

3.0

6.9
7.3

30 A 6.1
B9.0

(Note: Only schools used in both studies are included in the above.)

between the sickness rates is 1.7. While this differerce is not greater than
three times the probable error, the mere fact that it is greater suggests at
least a tendency for Type C rooms to be more conducive to respiratory illness
than those of Type B.

Minor respiratory illness insufficient to cause absence amounts to a rate
of 43 in Type B rooms and to 73 in Type C. This is a difference of 30.
The greater probable error is 9.0. The difference is thus more than three
times the probable error and statistically may be regarded as significant.
Interpreted in other words the system of fan ventilation representing Type
C is more conducive to respiratory illness among school children than the
window ventilation methods of Type B.

In Chart III are represented graphically the absence rates as well as
other facts pertinent to the matter. The difference in average temperature
between Type A and B rooms was 4.8 degrees. Relative humidity was almost
identical, being 46 per cent in the A rooms and 45 in B. The A rooms were
judged exceptionally fresh 63 per cent of the time as against 31 per cent
for B. The air possessed a noticeable odor 11 per cent of the time in A and
15 per cent in B. The degree of congestion was the same in both types,
namely: 11.5 square feet of floor space per pupil.

In the second comparison, the Type B rooms averaged 67.0 degrees
temperature as against 68.1 for the C rooms, a difference of but 1.1 degrees.
Relative humidity was 38 per cent in B and 40 per cent in C. The B rooms
were judged exceptionally fresh 18 per cent of the time, the C rooms 22 per
cent. Odor was noticeable 17 per cent of the sessions in B and only 14 in C.

The B rooms were appreciably more congested, the square feet of floor spa<
per pupil being 11.1 as against 14.7 in the C rooms.

The following conclusions appear justified from the evidence:

1. Kespiratory sickness is no greater in a window ventilated schoolrooi
kept around 59 degrees than it is in a room where temperature is 64.

2. Respiratory sickness is greater in fan ventilated rooms, such as are
represented in this study, than in window ventilated rooms, even though there
is not more than a degree difference in temperature, and the fan rooms are
more spacious.

3. It is low temperature rather than chemical purity of the air which
conveys the sensation of freshness.

DISCUSSION OF VENTILATION TYPES REPRESENTED IN THIS STUDY

The conclusions arrived at in discussing the relation of ventilation to colds
raise the question as to whether all methods of school building ventilation by
mechanical means are discredited by this test. This inference is of course
unwarranted. The results of this study apply only to the types of ventilation
here represented, a brief description of which will be given.

The selection of schools was made by the writer after a conference with
Mr. Frank G-. McCann, heating and ventilating engineer of the New York
City Board of Education. Altogether over fifty schools were considered, and
more than half of this number were visited in person by the writer.

There were many factors to weigh in making the selection. It was de-
sired above all to choose schools possessing all three types of ventilation. As
previously explained, this was found impossible except for one school. These
conditions were nearly fulfilled in one other instance w r here the three types
were found in two schools within a block or so of each other. For conven-
ience it was desirable that the schools should be located within Manhattan and
Bronx Boros. To represent this territory, selections were made in Lower
Manhattan, Central Manhattan and Upper Manhattan and the Bronx. It
was further desired that the ventilation methods should have already been in
use for some time prior to the experiment, so that uniform operating condi-
tions would be established. It was possible to adhere to this requirement in all
but one school, 165, in the first study and all but four in the second. In
these four, 165, 97, 115 and 33 Bx., window ventilation was arranged by block-
ing off the fan supply inlets to the rooms and by installing deflectors at the
windows. The effort was made to select schools whose mechanical ventilation
equipment was in good condition and in capable hands. Lastly it was essen-
tial that the principal of the school should be in sympathy with the objects
of the study.

Schools 12, 147 and 22 were located in lower Manhattan, the first on Mad-
ison and Jackson Streets; the second on Henry and Gouverneur, and the
third on Stanton and Sheriff. Schools 59 and 73 were in Central Manhattan,
the former on 57th Street near Third Avenue, the latter on 46th Street near

Third Avenue. School 165 was on 109th Street near Broadway; 39 on 126th
street near Second Avenue ; 2 Bx. on 169th Street near Third Avenue. The
schools added in the second study were 97 on Mangin Street between Stanton
and Houston, in the lower East Side ; 115 on 176th Street near Audobon Avenue ;
33 Bx. on 184th Street and Jerome Avenue, Bronx; 51 Bx. on Trinity and
Jackson Avenues, Bronx.

The date of erection of each building, as well as the type of building ven-
tilation is shown in Table XXII:

TABLE XXII

SCHOOL

DATE OP ERECTION

AERATION HEAT CONTROL REMARKS

AND ADDITIONS

1908

Window and Grav. Exhaust

Thermostatic

147

1898

Plenum Fan and Grav. Exh.

22.

1843-1873-1891-1902

1 1 1 1 1 1 11 f -t

t ^

1880-1902

Windows and Grav. Exhaust

Manual

1871-1904-1908

Plenum Fan and Grav. Exh.

Thermostatic Also air washer

165

1898-1905

< < ( < ( ( U

1903

Windows and Grav. Exh.

1 1

2 Bx.

1874-1886-1902

Plenum Fan and Grav. Exh.

51 Bx.

1915

Plenum and Exhaust Fans*

ft Also air washer*

33 Bx.

1899

Plenum Fan and Grav. Exh.

115

1914

Plenum Fan and Grav. Exh.

Also humidifying f;

1915

< (I (I 4 i ft

" Also air washer

*This refers only to the

two rooms used in the study.

The window ventilated rooms had direct radiation beneath the windows.
In the first study there were no deflectors except at School 73. In the second
study deflectors were provided in all rooms of Type A and B. All of these
rooms had gravity exhaust openings to permit air circulation. It is best that
these openings be in the inside wall opposite the windows. This arrangement
did not exist in many rooms, the openings being in walls adjacent to the
windows and frequently so small in size as to be really of little service in keep-
ing the room well aerated. Direct radiation was thermostatically controlled
in all cases save in School 73, where it was manually controlled.

The mechanical ventilation consisted usually of plenum fans, air being
driven into the classrooms near the ceiling and leaving through gravity exhaust
openings near the floor. These rooms were also provided with direct radia-
tion under thermostatic control. A check on the ventilation was had by means
of ribbons on the inlet. These were observed by the nurses, who could thus
tell in a rough way the efficiency of the blowers.

The system at School 147 gave a weak and irregular air flow to the three
classrooms during the first study, and windows were frequently opened. This
condition was greatly improved in the second study.

School 22 had a plenum fan system in the new wing. The air flow in the
rooms was continuous and pronounced, and windows were rarely opened.
Anemometer readings at the register face made on January 8, 1917, showed
1640 cubic feet per minute in Eoom 402, 1960 in 403 and 1620 in Room 404.

School 59 had a plenum fan system in the new addition built in 1908. This
consisted of two blowers and an air washer. This equipment was in most capable

hands, and the rooms were at all times well flushed with humidified and washed
air. Windows were always kept closed. On January 15, 1917, anemometer
measurements showed the following air flow in cubic feet per minute : Room
2031400, 2051300, 2061740, 5011150, 5031380, 505760. During
both studies there was continuous and pronounced flow in all rooms.

School 165 had a plenum fan system with gravity exhaust which proved
inadequate for the rooms used in the study. At times air flow was ample,
again deficient. Conditions were better in the second study.

School 2 Bx. consisted of an old and new section, the latter built in 1902.
This section contained the plenum fan ventilating equipment with gravity ex-
haust. Air flow was fairly continuous and pronounced.

The orientation of the classrooms varied somewhat in the three types,
the A rooms having a greater amount of southern exposure.

TABLE XXIII
ORIENTATION OF CLASSROOMS IN FIRST STUDY

VENTILATION

N., N.E.,

S., S. E.,

TYPE

N. W.

s. w.

RESULTS IN NEWER SCHOOLS ADDED IN SECOND STUDY

When this study was begun, there were no schools erected within two or
three years which could be used. In the second study we were enabled to
add four schools, three of which had just been opened to pupils within the
year. School 51 Bx. contained two rooms in which the Ventilation Commis-
sion was making studies on the effect of humidification, both being ventilated
by plenum and exhaust fans. These results were included in the grand
totals, but of course they do not furnish us with a comparison of the types
forming the basis of this study. The respiratory sickness rates were higher
in the humidified room. Temperature was about the same in both. Odor
was frequently noticeable in the humidified room.

TABLE XXIV
RESPIRATORY ILLNESS IN SCHOOL 51

VENTILATION
TYPE

ABSENCE
RATE

SICKNESS
IN AT-
TENDANCE
RATE

TOTAL
RESP.
SICKNESS
RATE

TEMPERA-
TURE

RELATIVE
HUMIDITY

PER, CENT

SESSIONS

ESP.
FRESH

ODOROUS

Humidified
Not Humidified

4.0
14.7

148.
50.

152.

64.7

67.6

67.4

39
2

School 33 was an older building, but because of work already in prog-
ress there by the Ventilation Commission, the sickness records were also col-
lected and added to the grand totals of this study. Ventilation was by

means of plenum fans and gravity exhaust. The fan inlets were blocked off
in the Type B rooms and deflectors placed at the windows. The respiratory
sickness rates were less in the two window ventilated rooms than in the
two of Type C. The fan rooms were slightly warmer but less odorous.

TABLE XXV
RESPIRATORY ILLNESS IN SCHOOL 33

PER CENT SESSIONS

VENTILATION

ABSENCE

SICKNESS

TOTAL

TEMPERA-

RELATIVE

ESP.

ODOROUS

TYPE

RATE

IN AT-

RESP.

TURE

HUMIDITY

FRESH

TENDANCE

SICKNESS

RATE

24.2
37.0

76.2
109.0

69.4
70.6

34
30

School 97 was just completed in 1915 and was equipped with plenum
fans and gravity exhaust, the air being washed and humidified before entering
the rooms. Three rooms were chosen to represent each of Type B and C.
The respiratory sickness rates were the lowest here of all the schools. Sickness
was less in the fan ventilated rooms than in the window rooms. The fan
rooms were a degree warmer and were much better aerated.

TABLE XXVI
RESPIRATORY ILLNESS IN SCHOOL 97

PER CENT SESSIONS

VENTILATION

ABSENCE

SICKNESS

TOTAL

TEMPERA-

RELATIVE

ESP.

ODOROUS

TYPE

RATE

IN AT-

RESP.

TURE

HUMIDITY

FRESH

TENDANCE

SICKNESS

RATE

5.6
3.7

52.6

40.7

66.7
67.6

32
3

The location of this school was along the East River, and across the
street was a large stable whose odors were frequently wafted over to the
school at times of east wind. This interfered with the free use of the windows.
The fan ventilated rooms were not troubled by these odors. One of the three
window rooms was on an enclosed court which also cut down free air circu-
lation. The experience at this school was very suggestive. Here was an il-
lustration where fan ventilation provided a more satisfactory result than
window ventilation. Schools with similar locations in the neighborhood of
noxious odors are evidently better served by indirect washed air than by tak-
ing air direct from the windows. The teacher of one window room was
well satisfied and much preferred it to the fan ventilation of the building.
The majority opinion, however, favored the fan rooms.

School 115, erected in 1914, was equipped with plenum fans, a humidifying
pan and gravity exhaust ducts. Air flow was at all times ample. Little or
no use was made of the humidifying pan. Respiratory sickness was greater
in the fan ventilated rooms.

TABLE XXVII
KESPIRATORY ILLNESS AT SCHOOL 115

PER CENT SESSIONS

VENTILATION
TYPE

ABSENCE
RATE

TEMPERATURE

RELATIVE
HUMIDITY

ESP.
FRESH

ODOROUS

30.4

47.2

67.6
67.6

28.
26.

2
1

3
6

(Note: The comparative data on sickness among pupils in School are not available for
this school.)

A great deal of dissatisfaction with the fan ventilation existed among
the teachers in this school. Complaints of dryness and drafts were common.
The window rooms were by far the more comfortable.

In the three schools added in the second study, where Types B and C were
studied, the window rooms showed less respiratory illness in two, and more
in one. This supports the findings in the other schools.

In view of the favorable showing for fan ventilation in a very modern
school with humidification such as 97, it may appear that the results of this
study do not apply to installations of the latest design. It is true that we
cannot generalize too widely in the matter, but on the other hand, School 59
possessed very modern equipment and was operated in every way as per-
fectly as 97, and yet the sickness rates here were higher than in the other rooms
crudely equipped for window ventilation.

The buildings used were representative of what existed in New York City
at the time. All were not of the very latest construction; nor were all of
ancient pattern and design. All types were represented. The buildings
were equipped and built with plenum fan ventilating systems. These systems
were not ideal. They possessed faults as judged from the ventilating engi-
neer's viewpoint of the year 1915.

The rooms fitted up for window ventilation were not built for this pur-
pose. They were altered for the plan in mind. In no instance were the fa-
cilities complete.

As a comparison of average fan ventilation in New York City school build-
ings and ventilation of the same buildings without fans, the present study
is entirely fair. If either type of room is lacking in its equipment, it is the
window ventilated rooms which labored under the greater handicap.

METHODS OF RECORD TAKING

A word may be devoted here to the method of collecting records.

Each classroom was visited morning and afternoon. In the morning a
record was made of the pupils absent and of the pupils in attendance who
exhibited signs of a cold. The cause of absence was ascertained by a visit to
the home. If a physician were in attendance his diagnosis was accepted. If
110 physician were in attendance, the nurse diagnosed the case, and when in
doubt, her opinion was checked by a medical inspector. Many absences were
not due to illness, as the subsequent records will indicate.

The diagnosis of minor illness among pupils in school was made by the

nurse. Many pupils with symptoms of a cold were pointed out to the nurse
by the teachers.

At the beginning of the afternoon session the nurse again visited each
room to ascertain absences, and the causes were determined in the usual man-
ner. No effort was made at this time to determine illnesses among those pres-
ent. A child recorded as having coryza in the morning was credited with
the same affection in the afternoon if he or she were present in school.

In addition to the routine described above, the nurse entered each class-
room at about 10:30 A.M. and 2:15 P.M., or just prior to the midsession
aeration of the room, and recorded her impressions of the air conditions and
made determinations of temperature and humidity with a sling psychrometer.
The actual procedure was to enter the room, walk down the side aisle to the
rear and thence up the middle aisle to the center of the room. The impres-
sion of odor was then recorded in terms of the scale given below. Next
in order were recorded the sensations of temperature, moisture and air motion
in terms as shown. The psychrometer was then swung at a level of about
three to four feet from the floor, the wet bulb having been moistened from a
small bottle of water carried for the purpose, and both wet and dry bulb
readings noted.

VOTING SCALES OF SENSE IMPRESSIONS
ODOR TEMPERATURE MOISTURE AIR MOTION

Exceptionally

fresh

Too warm

Moist

Dead

Odor absent

Satisfactory

Neutral

Bet. R & T.

Breezy or

Odor

Cool

Dry

drafty

Before departing, the nurse made notations of the position of windows,
whether open or closed, position of door and transom and activity of flag at-
tached to the inlet register in the fan ventilated rooms.

Prior to the beginning of the study the nurses were carefully rehearsed
in their duties and were given demonstrations in the use of the sling psy-
chrometer.

The diagnosing of respiratory illness was frequently checked up by
medical school inspectors and the supervising physician of the study, Dr. Leo-
pold Marcus.

For several weeks during the second study all diagnoses were made by
medical inspectors. Their opinions fully confirmed the interpretations made
by the nurses and verified the casual inspections of physicians made prior to
this time.

Respiratory illness is responsible for 19 per cent of absences from school ;
illness other than respiratory (including, however, the acute contagious dis-
eases) 37 per cent ; and causes other than illness 44 per cent.

THE SCHOOL PERSONNEL AND RESPIRATORY ILLNESS

The personnel of the pupils is a marked factor in determining the respira-
tory illness rates distinct from environmental influences. This was recognized
at the outset, and an attempt, but partially successful, was made to equalize

this influence among the three ventilation types. Some schools were high in
respiratory illness in both studies, while others were low in both.

Considering the total respiratory illness rates for both studies, Schools
12 and 147 had the lowest figures. These schools are on the lower East Side
in the heart of the Russian-Jewish districts. The buildings are old. The
average temperature was around 64 degrees. These two schools may be
contrasted with Schools 165 and 115, which were located in very good neigh-
borhoods and were attended by native "born children of well-to-do parents.
Both are of more recent construction than 12 and 147, P. S. 115 having been
erected in 1914. In spite of environmental and social advantages, the upper
Manhattan schools had high rates from respiratory illness.

In general, the schools located in congested districts and attended by
pupils of inferior economic and sanitary status had less illness than those
located in the better class neighborhoods.

Averaging the rates by social and economic status, the above facts stand
out clearly.

RESPIRATORY ILLNESS RATES

SOCIAL AND AMONG THOSE

ECONOMIC STATUS SCHOOLS ABSENT IN ATTENDANCE

Very good 165, 115, 33 34.7 78

Good 59, 2 Ex., 51 Bx. 10.6 85

Poor 12, 147, 22, 97, 73 7.6 35.4

Very Poor 39 10.8 21.6

An explanation of this unexpected result is not easy to give. It prompts
the query Does prosperity undermine health and are our children of supe-
rior social status coddled to their detriment?

It is entirely possible that the children in the poorer districts acquire a
more specific immunity by reason of their congested manner of living. It
has been shown by Vaughan and the writer that the city boy made a hardier
soldier in our army camps in 1917 and 1918 and was less subject to disease
than the country boy.*

It is also possible that the pupils in the poorer neighborhoods become
"hardened" by slight exposure to cold, the body becoming less sensitive
to environmental changes. Overheating and overeating are drawbacks to
which this class is less familiar than their more fortunate schoolmates. In
many respects material success converts a man into a less perfect physiologic
machine. As the battle with the elements becomes less severe, the stimula-
tion to physiological combativeness wanes. Lack of exercise, complex food
as distinguished from simple coarse food, and life in uniformly and highly
heated buildings without question weakens the body physically. In these
statements may be found the explanation of this peculiar distribution of the
ordinary forms of respiratory illness.

In view of the fact that the Type C rooms had more girls than the others,
the question arises as to whether this would not account for the greater ill-

*"Communicable Disease in the National Guard and National Army of the United States During
the Six Months from September 29, 1917, to March 29, 1918." By Col. V. C. Vaughan and Capt. T.
G. T. Palmer, Jour, of Laboratory and Clinical Medicine, Vol. Ill, No. II, August, 1918. Pages 693-693.

ness.** This presupposes that girls are more susceptible to colds than boys,
a supposition for which there is no justification so far as we know. There is
no indication of this in the present study.

In the first study, P. S. 165, Type C had the highest respiratory absence
rate, yet only 28% of the pupils were girls. The next highest rate was at P.
S. 2, Bronx, Type B, where 50% of the pupils were girls. The third highest
rate was at P. S. 165, Type B, where all the pupils were boys.

P. S. 2, Bronx, Type C, had high illness rates in the second study and yet
only one-third of the pupils were girls.

P. S. 12 and 147 had low rates in both studies and the ratio of girls
to boys was four to one in the first study and three to one in the second.

TYPES OF RESPIRATORY ILLNESS

Lacking the diagnosis of a medical man as to the specific type of respira-
tory illness in all instances of this study, we cannot publish these facts with
any degree of certainty. However, we submit the statements of the nurses,
which it will be remembered were frequently checked by the medical school
inspectors.

The most prevalent form of respiratory illness causing absence was ton-
sillitis, which amounted to 32 per cent of the total. Slightly less prevalent
were coryza (25%) and bronchitis (22%). Laryngitis and pharyngitis were
less frequently mentioned.

Of the illnesses among those present in school, coryza representing 62% of
the total, is the most prominent. Bronchitis stands second with 20% and
laryngitis third with 10%.

Tonsillitis is especially prevalent in the Type C rooms. Other affections
are greater in Type C, but no one affection seems to be characteristic of any
ventilation type.

Illness other than those listed under the term (e respiratory illness" were
due to a great many causes. Diphtheria, scarlet fever, measles and chicken-
pox were responsible for a small amount of absence, but absence from these
causes combined amounts to less than that due to tonsillitis alone. In the
first study the indefinite term "sickness" was given as responsible for more
absence than any single cause. More specific terms were used in the second
study. Headache was a frequent cause of absence, being mentioned most
frequently in the Type C rooms. Appendicitis was responsible for a number
of absences. A miscellaneous group of innumerable causes makes up the
bulk of the absence causes. No particular form of illness seems to charac-
terize any ventilation type.

WEATHER AND RESPIRATORY ILLNESS

Although aside from the ventilation question it is of interest to note the
fluctuations in respiratory illness from week to week and the corresponding
changes in weather. From the preceding pages it is evident that the indoor

**The percentage of girls in Type C was 60 in the first study and 54 per cent in the second.
The figures for Type B were 37 and 31 and for A, 41 and 49.

atmosphere has an influence on health. By combining the records of all schools
it will be possible to follow the seasonal change in respiratory illness.

In Chart IV we have shown the sickness rate in each type of ventilation
by weeks along with the room temperature and relative humidity. The data
for Schools 97, 115 and 51 Bx. are omitted, as records were available only

150
l5
IOO
75
50

bO
55
50

55
50
45
40
35

FIRST STUDY
FE.B. 14 - APR.lSjgik,

SECOND STUDY

OCT. 30- JAN.2fc,l9T7

II 1 I 1

TOTAL f?ESP RATORY SICKNESM
Rates bv weckj

._^

-X

' -^

-^.

^^-

_-^^

^^_

-''

fT~~

*.--

^.*^i

_^x^

-^*^_

ROOM TEMPtFJATURE

-^4

&,.

~J7

J /;

-,^

v\\

'\N

- x

"^"

1 f

tLATIVE HUMIDITY
IN CLASSROOMS

" x <

WEEKLY INCIDENCE OF TOTAL RESPIRATORY
ILLNESS IN CLASSROOMS VARIOUSLY VENTILATED

Data from a/1 schools included
t ACept 97, 115, 31 Bx ^
A- Cold, wi- Jo* venti atd rooms (about 5 )
B- Cool, window vent,latd room* (about 65*)
C- fan- ventilated room* (about 69'}

Chart IV.

during the last seven weeks of the second study. The fan ventilation group
shows the greatest amount, and the window ventilated, moderate temperature,
the lowest amount of respiratory illness throughout.

Respiratory illness declines from February to April although the fan ven-
tilated rooms show the highest point during the middle of March. Colds

are at a higher level in October than they are in April. In the Type C and
B rooms colds increase abruptly during the first 5 weeks in the Autumn.
Type C then holds this level. The B rooms fall off and do not rise again until
January. Colds in the Type A rooms increase gradually from October till

RESPIRATORY ILLNESS AMONG- SCHOOL CHILDREN
AND IT'S ASSOCIATION WITH THE. WEATHE.R
By Weeks

FIRST STUDY StCOND STUDY
8weeks Feb 14,- Apr. 6,l9ife I2*veeks Oct. 30, 1914,- Jan 26, (917

90
70
50
JO

90
75
60
45

TO,

"-**.

,^-=

.--*

^^<

-~~"

OUTDOOR WEATHLR RECORDS

"--.

_..-'

*..

" ^.

"*N.

% x

30
70

50
40
30

Mean Temper-afore iQAM-PM

^-^1

i^-^

* ^

"^-x.

\ X

Per Cent of Fbasible Sunshir

J V

veroge Change inTe

-npcraturel

70
65
fed
55

6
5

3
2

10
8

K-*"^

h "v.

^^- -

^^~

I 1 I

MQ^ Relative Hun

n.dily

^vj^.

./*

^ IV N N

'****^

(

fMeon Hours Roin or SnowfoJ

I pr dc^

-\-

-/-

i^*-

^^^

s^^

Mon Do. Iv W.nd Velocity

Chart V.

the first week in December. From this point they decline only to rise again
the latter part of January.

Room temperature in the fan ventilated rooms is the most uniform, keep-
ing quite constantly between 68 and 69 degrees. In the window rooms Type
B, temperature has a slightly wider variation, from 65 to 68 degrees, but is
consistently below Type C. In Type A rooms we note a wide variation,

from 55 to 66. During February and March these rooms run between 50
and 60, and this is true also in December and January. In April and Novem-
ber the temperature is from 60 to 65.

Kelative humidity is greatest in the A rooms. It is lowest in March and
January. As will be seen from a later chart, humidity is influenced mostly
by outdoor temperature and next to that by outdoor moisture.

Total

Respiratory
S/ckness
Pate.
Weather

Corn fort

Vote.

RESPIRATORY ILLNESS, WEATHER AND THE
SENSATION OF WEATHER

Mean Outdoor
Temperature

Total Deheating
Potver <*^
\Heather~

The general points to be noted from this chart are that colds are more common
in fall than in late winter, that even though the room temperature and humid-
ity in Types B and C are quite similar, there is an appreciable difference in
the prevalence of colds, and finally that the course of respiratory illness from
week to week is guided mainly by influences other than the temperature and
humidity of the classroom.

That outdoor weather bears a close relationship to colds is illustrated
by the various graphs on Chart V. Far overshadowing other weather in-
fluences is temperature. In the spring, colds decrease as the weather becomes
warmer. In the fall, oncoming cold weather is coincident with increasing
respiratory affections.

^
/

i ~

6O ^^*

' ^_

-*.

Mild

Cole

Not"!

suffic

lent t

i caus

abs<

nee

rom

schoo

Week Ending 3 10 n 24 1 8 15 22 5 \Z \9 fJb,
MOV ^ DEC JAN.

^5^

4 .

Sever

e Co

LSI Q

_absc.

vce

rom

scho

ol.

Week Endmo 3 >0 7 Z4 -l 8 |5
NOV. DEC.

22 5 12 19 2fc

,c 00 DeatKa from Pneumonia

Y///

OCT NOV. DEC
THE SEQUENCE OF COLDS AND PNEUMONIA

JAN.

NEW YORK CITY 1916-1917

Colds among 3000 school children expressed
as a rate per 1000 pupil session registration
units.
Total deaths from pneumonia (all forms)
in New York City.

Chart VII.

What is understood as changeable weather does not have marked influence
on colds. The third week in February shows an extreme daily change in
temperature with no accompanying increase in colds.

Relative humidity shows wide variations from week to week without corre-

spending undulations in the sickness curve. The late winter is more blus-
tery than the fall, and yet colds are less numerous in the windy season.

Temperature and colds are most closely related. Is it temperature per
se or the total chilling effect of all weather elements combined? The formula
derived by Dr. Leonard Hill of England from his instrument known as the
kata-thermometer permits us to sum up in a single expression the combined
deheating effect of cold, evaporation and wind action.* From the mean
daily outdoor temperature, vapor pressure and wind velocity we have com-
puted the mean " total H" or total deheating power of the elements. This
graph has been placed alongside curves for respiratory illniess in the
second study, and mean temperature and a fourth curve labelled " comfort."
The comfort vote is a summary of the recorded daily impressions of the tem-
perature feeling of the weather, as judged by three members of the staff
of the Ventilation Commission.

The kata and temperature curves closely parallel each other. In some
respects the kata curve is more closely associated with the rise and fall of
illness than the temperature curve. Thus, the kata curve shows increasing
cold for the first four weeks corresponding to increasing illness. The tem-
perature curve shows no increase in cold in the fourth week over the third.

Illness falls off as the temperature stabilizes. In the 7th week tempera-
ture again descends, and sickness picks up. The 10th week is much colder as
judged by the kata reading although the temperature is no lower. There is
however, very low humidity and high wind velocity, which are heat extrac-
tors. These data suggest that it is the total chilling effect of the atmosphere
rather than low temperature alone that is conducive to illness.

The curve of outdoor temperature comfort closely parallels the temperature
curve, more so than the kata curve.

The sequence of mild colds in November, followed by heavier colds in
December and then by pneumonia in midwinter, is strongly suggestive of a
progressive weakening of vitality. Our mid-winter pneumonia peak is thus
the result of attrition of vital resistance caused, among other things, by acute
respiratory affections in the months preceding.

SUMMARY AND CONCLUSIONS

Prom the results of this study there appears to be something inherent in
the indirect method of ventilating schoolrooms by means of forced draught and
gravity exhaust, as practiced in this study, that is productive of respiratory
affections, something which is not present in rooms ventilated with windows
and gravity exhaust. What these unfavorable elements are is not entirely
clear. Higher temperature is one. Uniformity of temperature and air flow
is another. Uniformity is characteristic of the fan ventilated room. In an
unvarying atmosphere the occupants miss that pleasant stimulating effect.
Evidently the absence of this quality affects health adversely as well as
comfort.

*"The Measurement of the Rate of Heat loss at Body Temperature by Convection, Radiation
and Evaporation." By Leonard Hill, F. R. S., O. W. Griffith and Martin Flack, Philosophical Trans-
actions of the Royal Society of London. Series B. Vol. 207, pgs. 183-220. 1916.

The temperature of window ventilated schoolrooms may be reduced as low
as 59 degrees without increasing the prevalence of colds.

It must not be inferred that window ventilation- as represented in this
study was uniformly satisfactory. It was not. As a rule the rooms exposed
on the east do not fare as well as others. Ample exhaust openings are
better than those of small area. There is the matter of location of outlets
with respect to the windows, location, size and control of direct radiation,
window deflectors, etc., which affect the success of window ventilation. All
of these factors must be studied.

In spite of our inadequate knowledge of window ventilation at its best,
the fact remains that the window rooms of this study, even though of crude
arrangement and not built originally for the purpose, competed on favorable
terms, from a hygienic and aesthetic standpoint, with the most elaborate
and costly fan and duct equipment. The tendency in the past twenty years
has been away from natural and toward mechanical ventilation. The time
and effort of the heating and ventilating engineer has been directed toward
the perfecting of mechanical means for aerating buildings. What would
the same amount of effort have yielded if expended on the development of
natural ventilation? Possibly something of great value and at less expense.

Because window ventilation is practicable for the ordinary schoolroom,
it does not follow that the assembly room, the theatre and other places
seating several hundred people can also be dealt with in this manner. Each
type of enclosure must be handled as a distinct problem. Natural ventilation
has its limitations. That the schoolroom is not beyond these limitations is
the indication of this study.

The factors which, above all others, promote comfort, health and effi-
ciency are coolness and fluctuating air motion. If the teacher maintains her
classroom in a changing condition, without draughts, between 64 and 70
degrees, with the mean lying nearer the lower figure, it matters little from
a practical standpoint what the other measurements of ventilation indicate.
To this standard the room properly equipped with window ventilation and
gravity exhaust, can readily conform.

In its quantitative effect on respiratory illness school ventilation is of
much less moment than the outdoor weather influence. Respiratory affections
increase with the onset of cold weather. They diminish with the advent of
mild weather in the spring. Wind and humidity accentuate the temperature in-
fluence. Sunlight exerts at least a warming influence sufficient to modify
the unfavorable effect of cold. Abrupt changes in temperature do not in-
fluence respiratory illness as much as one might expect from everyday
experience.

The sanitarian is interested in the prevention of the tremendous increase
in the mortality from the pneumonias, which occurs in cold weather. If it
is possible to mitigate the unfavorable weather effect by the proper regulation
of the indoor atmosphere, it behooves the public health fr&ternity to bend
every effort toward this goal. The problem is an alluring one. The results
of this school study hold forth much promise in this direction.

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1939

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