key: cord-0867778-ntfmadgx
authors: Israel Nazarious, Miracle; Mathanlal, Thasshwin; Zorzano, Maria-Paz; Martin-Torres, Javier
title: PRessure Optimized PowEred Respirator (PROPER): a miniaturized wearable cleanroom and biosafety system for aerially transmitted viral infections such as COVID-19
date: 2020-10-06
journal: HardwareX
DOI: 10.1016/j.ohx.2020.e00144
sha: 998f59e73d48799de21f4488b6a0b6e8bee5658f
doc_id: 867778
cord_uid: ntfmadgx

The supply of Personal Protective Equipment (PPE) in hospitals to keep the Health Care Professionals (HCP) safe taking care of patients may be limited, especially during the outbreak of a new disease. In particular, the face and body protective equipment is critical to prevent the wearer from exposure to pathogenic biological airborne particulates. This situation has been now observed worldwide during the onset of the COVID-19 pandemic. As concern over shortages of PPE at hospitals grows, we share with the public and makers’ community the Pressure Optimized PowEred Respirator (PROPER) equipment, made out of COTS components. It is functionally equivalent to a Powered Air Purifying Respirator (PAPR). PROPER, a hood-based system which uses open source and easily accessible components is low-cost, relatively passive in terms of energy consumption and mechanisms, and easy and fast to 3D print, build and assemble. We have adapted our experience on building clean room environments and qualifying the bioburden of space instruments to this solution, which is in essence a miniaturized, personal, wearable cleanroom. PROPER would be able to offer better protection than an N95 respirator mask, mainly because it is insensitive to seal fit and it shields the eyes as well. The PROPER SMS fabric is designed for single-use and not intended for reuse, as they may start to tear and fail but the rest of the parts can be disinfected and reused. We provide a set of guidelines to build a low-cost 3D printed solution for an effective PAPR system and describe the procedures to validate it to comply with the biosafety level 3 requirements. We have validated the prototype of PROPER unit for air flow, ISO class cleanliness level, oxygen and carbon-dioxide gas concentrations during exhalation, and present here these results for illustration. We demonstrate that the area inside the hood is more than 200 times cleaner than the external ambient without the operator and more than 175 times with the operator and in an aerosol exposed environment. We also include the procedure to clean and disinfect the equipment for reuse. PROPER may be a useful addition to provide protection to HCPs against the SARS-CoV-2 virus or other potential future viral diseases that are transmitted aerially.

Abstract: 13 14

The supply of Personal Protective Equipment (PPE) for reuse, as they may start to tear and fail but the rest of the parts can be disinfected and reused. We 28 provide a set of guidelines to build a low-cost 3D printed solution for an effective PAPR system and describe 29 the procedures to validate it to comply with the biosafety level 3 requirements. We have validated the 30 prototype of PROPER unit for air flow, ISO class cleanliness level, oxygen and carbon-dioxide gas 31

concentrations during exhalation, and present here these results for illustration. We demonstrate that the 32 area inside the hood is more than 200 times cleaner than the external ambient without the operator and 33 more than 175 times with the operator and in an aerosol exposed environment. We also include the 34 procedure to clean and disinfect the equipment for reuse. PROPER [1] . Many hospitals are facing rapidly dwindling 52 supplies of essential safety equipment such as respirators. This equipment is very important for the usual 53 care of patients with COVID-19 as they prevent the wearer from exposure to pathogenic biological airborne 54

particulates and from contact with contaminated surfaces. These airborne particulates or aerosols 55 generated by the patients with COVID-19 poses additional risk to HCPs [2] . Patients As concern over shortages of PPE at hospitals worldwide grows, the Centers for Disease Control and 73

Prevention (CDC) has provided recommendations for HCPs managing the COVID-19 outbreak to optimize 74 the supply of PPE and equipment [5, 6] . assembly. The components of Figure 1 , and the design criteria, are presented in the following subsections. 118 119 120 Figure 1 : Schematic of the components used in the PROPER assembly. adaptor is secured to the hood with a flange fitted in the exterior of the hood (see Figure 3 ).

The 3D Figure 4 shows the components to build the PROPER hood assembly where each component has its 309

individual designator code. Some of these components are 3D printed prior to this procedure. fitting.

Step face. Figure 6 : (Left to right) Procedure to attach the curved face shield frame and helmet fitting to the SMS 344 hood fabric.

Step 3: Securing the ratchet knob and hood adaptor assembly.

Step 5: Securing the air pathway with adaptors and attaching the centrifugal fan Step bag.

Step 10: Completing the power supply and conditioning unit 463

hole to the USB-A slot in the powerbank (P1) as shown in figure 15 (left) . This procedure completes all the 465 electrical connections in the power supply and conditioning unit and readies the PROPER unit for operation. 466

Remember to fully charge the powerbank (P1) before every operation.

468 Figure 15 : (Left to right) Procedure to complete the power supply and conditioning unit.

Step 11: Connecting the breathing tube between the hood and the FFU The procedure for donning the cleanroom garment has been described in accordance with the guidelines 481

stated

Step 1: Donning the PROPER begins with a hand hygiene procedure and putting on the cleanroom garment. The steps are briefed as follows:

2. The cleanroom garment must be chosen based on the correct size. 3. Hand hygiene needs to be ensured using a hand sanitizer. 4. Cleanroom garment is worn with all the ties on the garment secured. Assistance may be needed by other healthcare professional for securing the ties.

Step 2: Once the cleanroom garment has been worn, the hood needs to be placed on the head.

Step 3: The shroud of the hood is inserted under the overall garment and zipped up.

Step 4: The ratchet knob is tuned by rotating in clockwise direction and anti-clockwise direction ensuring that the PROPER hood is firmly secured to the head.

Step 5: The hip bag is secured around the hip using the strap and buckle. Ensure that the hip bag is secured in a comfortable manner.

Step 6: Connect the breathing tube to the hood adaptor. A click sound ensures that the connection is perfectly sealed.

Step 7: The PROPER fan unit can now be powered ON.

Step tape to provide an airtight seal. Figure 19 shows the air flow results during half an hour of nominal PROPER 565 operation. (2), 590

(2) =

The nearest whole number is 1, thus we sampled in one location. The head of the particle counter was 594 placed directly inside the center of the hood and mixing of air from the ambient environment is cut off by 595

folding the shroud of the hood fabric around the base of the particle counter and securing with a strip of 596 masking tape to provide an airtight seal. 597 598

We measured the particle count with a target cleanliness class of ISO that generated a distribution of aerosols whose size has been quantified within the ranges of 0.3 μm. 0.5 615 μm, 1 μm, 2 μm, 5 μm and 10 μm. The particle concentration was counted inside the hood with the help 616 of a sampling tube, see Figure 20 . 622 Table 4 shows the results of particle count inside the hood during PROPER operation (with and without 623 operator) and in the ambient environment outside the hood (Sample 1 and 2) . The results of operation of 624 PROPER in the aerosol environment with different particle distribution (Sample 3) is also provided to 625 demonstrate the efficiency in filtration. 

where, c o = concentration in unpurified air (outside the hood) and c = particle concentration of purified air 641

(inside the hood without the operator). and hood inside a clean environment. This prevents the contamination of PROPER components and ensures 647 that the particle count is within the certified ISO class. However, since the measured particle count and the 648 certified ISO class 6 is without an operator (due to practical difficulty of fitting the particle counter with 649 the operator), we foresee that additional particles from operator's hair and breathing may be introduced 650 inside the hood. However, all these particles would come from the healthy operator and most of them 651 would be removed with wipes during the cleaning phase. The purpose of the particle count validation is to 652 demonstrate that the use of a fan with a filter, allows to reduce by two order of magnitude the income of 653 particles above 0.3 µm size into the "wearable clean zone". 

Experiment setup to determine the oxygen, carbon-dioxide gas concentrations and overpressure 675 inside the hood of PROPER during an hour of continuous demonstration, (left) without the operator inside 676 and (right) with the operator inside

Figures 22 show a comparison of the evolution over time of gas concentrations inside the hood during an 678 hour of nominal PROPER operation, without an operator, and while it is donned. The carbon-dioxide 679 concentration inside the hood spiked up until the PROPER was turned ON. The gas concentration gradually 680 reduced as shown in figure 21 (orange curve), as a result of fresh purified air being pumped in the hood at 681 a rate of about 5 CFM while maintaining an overpressure of 0 to 4

The carbon-dioxide concentration stabilized around 570 ppm (within typical range of 400-1000 683 ppm in occupied indoor spaces with good air exchange [35]) around the same level as when PROPER was 684 in operation without donning (cyan curve). The average ambient carbon-dioxide concentration outside the 685 hood was 435.11 ppm. The oxygen concentration was always hovering around the nominal 21 % (not 686 shown). The average temperature inside the hood during the hour operation as 30.6 ⁰C with an average of

Uniform Requirements for manuscripts submitted to Biomedical journals

Stakeholders for Non-NIOSH-Approved Imported FFRs

Powered air-purifying respirators (PAPRs) help doctors and nurses treat coronavirus patients

Considerations for Optimizing the Supply of Powered Air-Purifying Respirators (PAPRs

Emergency Use Authorization (EUA) information, and list of all current EUAs

779 approved-respirators-during-covid-19-pandemic 780 [10] Decontamination and Reuse of Filtering Facepiece

To verify that the exhaled gas is safely "leaked" out through the fabric and other tiny air gaps and to 658 determine the buildup of gases during inhalation and exhalation inside the hood of PROPER, we measured 659 the oxygen, O 2 , and carbon-dioxide, CO 2