The overlooked elastomeric respirator
Dr Alexander Clarke, Anaesthesia Fellow, VIC
Dr Chloe-Maryse Baxter, Paediatric registrar, VIC
Dr Cameron Graydon, Anaesthetist, QLD
“One elastomeric could do the work of hundreds of N95s, maybe thousands, and would occupy a fraction of the storage space.” — New York Times feature, May 2020
There are 4 main types of air purifying respirators shown below:
What are the levels of particulate filtration?
The nomenclature around particulate filtration can be confusing. In Australia, we define P1, P2 and P3 as the levels of particulate filtration. P2 is the minimum appropriate for healthcare use (N95 equivalent). P2/N95 does not refer to the shape/type of the respirator, only the level of protection.
- In Australia, AS (Australian Standard) 1715 defines the terms and types of respirators. AS1715 also defines the level of particulate protection required for different types of microorganism hazards. The gold standard for protection from microorganisms is the “PAPR—P3 filters in PAPR with full facepiece or head covering and blouse or full body air-supplied positive pressure suit”. PAPRs are the most effective, followed by full face, followed by half face elastomeric respirators
Single use surgical masks are described in AS 4381. They do not provide protection against airborne contaminants and are explicitly described in the standard as being ineffective against surgical plume and airborne microorganisms.
We will focus on elastomeric respirators from here.
Elastomeric respirators may be half facepiece or full facepiece tight-fitting respirators where the facepieces are made of synthetic or natural rubber material. They have exchangeable cartridge filters, and can be repeatedly used, cleaned, disinfected, stored, and re-used. They are available as alternatives to disposable half mask filtering facepiece respirators (FFRs), such as P2/N95 FFRs. Some types of elastomeric respirators can offer higher assigned protection factors (APFs) than N95 FFRs.
Elastomeric masks are being used in US hospitals (eg. Yale New Haven, University of Maryland-Baltimore Hospital, Allegheny Health Network) and the NHS in the UK and protect against shocks and shortages to the supply chain.
Elastomeric respirators have some practical challenges, including fitting and cleaning, but the primary obstacles to wider adoption have been cultural and economic: concern about the masks’ industrial appearance and reluctance to consider alternatives when N95s were cheap and abundant. Full face elastomeric respirators replace 3 items of PPE (face shield, goggles and mask) with one item, reducing the opportunity for doffing errors and self-contamination.
Advantages over disposable N95 masks?
- can be more comfortable and used for prolonged periods (Chlikonda et al)
- fit-testing shows very high rates of success
- full-face elastomeric respirators provide significantly better protection than FFRs
- masks can be reused by different workers – with masks decontaminated after each shift.
- cost effective with savings of up to 95% vs disposables.
- reduced pressure to adopt compromised solutions such as extended use or re-use of disposable respirators.
- can look confronting for others
- may interfere with communication and downward gaze (some products)
- require training and fit-testing before use
- they require maintenance and replacement of filters, valves, covers and straps over time.
No type of respirator or surgical mask (including disposable respirators) is rated to filter exhaled air. Reusable respirators with exhalation valves are not TGA approved for use in surgical fields. A surgical mask may be placed over the exhalation valve if there are concerns about trapping large exhaled particles (source control).
What is the evidence?
In a US study involving 2,000 nurses and doctors working in ED, ICU, and anaesthetics, none of the participants wanted to return to disposable FFR N95s after the month-long trial. Patients were reportedly receptive to their carers wearing the masks and the cost-savings were considerable (<10% of the cost of N95s).
Half face elastomeric
Loose-fitting (3M Versaflo)
Tight-fitting PAPR (CleanSpace Halo)
Powered air purifying respirators (PAPR): positive pressure driven by a motor. PAPRs can provide protection up to 100x more effectively than a disposable N95 mask.
Fit testing is required for all types of tight fitting respirators, including elastomerics.
Fit testing must be performed for the exact mask (brand, model, size) that is to be used by the employee.
Fit testing for elastomeric respirators can be performed with non-destructive qualitative or non-destructive quantitative means. This means that the evaluation does not destroy the respirator in the process of fit testing.
Quantitative fit testing for a full face elastomeric mask
Quantitative fit testing can be performed for all types of tight fitting respirators but is required for full face masks and tight fitting PAPRs.
A summary of respirator characteristics:
The cleaning process typically involves 1) using soap and warm water and/or chemical disinfectants authorized for use with their specific elastomeric facepiece components and 2) discarding the filter cartridge after a specified number of uses (broad range from single use to 6 months). Bessesen et al. provide useful guidelines for cleaning and disinfecting elastomeric respirators in healthcare environments.
Specific manufacturer guidelines vary but here is some guidance:
- 3M Elastomeric filters: “This hard case can be cleaned by wiping the outside surface with a damp cloth soaked in disinfecting solution until visibly wet for the appropriate contact time and then removing the disinfecting solution with a clean, water-soaked cloth and air drying. “
- 3M Elastomeric facepieces: “Sodium hypochlorite solution (at a free chlorine concentration of 5,000 ppm) with 1-minute contact time”
- Sundstrom Elastomeric Half-face Respirator: According to the Sundström user manual and operating instruction, the SR100 can be cleaned with the Sundström cleaning wipes or, if heavily soiled, can be washed in warm water (40°C) in a soap solution with a soft brush. After cleaning the SR100 should be rinsed, disinfected and dried. Disinfection can be performed using a 70% ethanol or isopropanol solution.
- The SR100 may also be washed in a decontamination washer similar to the Solo Rescue used in industry or a batch thermal washer (e.g. Getinge 8666 batch washer). This is for decontamination only and is performed at a temperature not exceeding 60°C. After washing the mask should be rinsed, disinfected (in a 70% ethanol or isopropanol solution) and dried according to the manufacturer.
Not all centres are performing the disinfection step. Some, like Yale New Haven, a 4500-bed health service in the US, argue that a hot wash with detergent is sufficient to kill the virus and sterilisation is not necessary.
Safe donning and doffing
- Simple with disposables
- Simple with elastomerics
- Complex with certain PAPRs, easy with others
- Disposable respirators are single use. They cost approximately $3 per use.
- 3M half face elastomeric respirators with filters cost $50-$150. They can be used indefinitely.
- Full face elastomeric respirators with filters cost approx $300-350
- PAPRs typically cost $1200-$2000 and can be used indefinitely.
- In the healthcare environment where there is a low volume of respirable material to be filtered, filter lifespan for both PAPRs and reusable elastomeric masks is high. This is very different in industries like mining where particulates clog up filters.
- The environmental cost of disposable respirators is high
- Total cost of respiratory protection for one staff member using 4 disposable FFRs per day is approximately $3,120 ($3 x 4 per day x 5 days a week x 52 weeks a year).
- The equivalent reusable half face elastomeric with two sets of filters would cost $50 + $20 = $70, a 97% saving.
- A full face version with 5x higher rated protection would cost $300 + $20. Face shields and disposable goggles cost approximately $1, therefore the savings amount to 91%.
- There is a long history of the safe, effective use of elastomeric respirators in healthcare settings. JAMA March 2020 and the National Academy of Sciences, Engineering and Medicine and the CDC have excellent reviews on the subject.
- Patient acceptance
- There are no reported concerns regarding patient acceptance or fear in the published literature.
- Staff acceptance
- Industries where respirators are used routinely use reusables
- Healthcare staff find reusables more acceptable than disposables in high risk settings.
With the current constraints in the global supply chain, alternatives to disposable N95 respirators must be considered. The alternatives are well validated and their use in healthcare supported by the relevant standards organisations.
Healthcare settings could transition to the use of reusable elastomeric masks and provide effective respiratory protection to staff for the foreseeable future. This would also alleviate concerns regarding disposable respirator availability. Fit testing of reusable respirators could be freely performed without regard as to any effect on stock availability because destruction of masks does not occur.
The majority of Australian healthcare settings do not comply with standards around respiratory protection outlined here. These issues could be readily addressed with a transition to alternative respiratory protection devices, when incorporated in a comprehensive respiratory protection program as outlined by AS 1715 and 1716.