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Brief Reports, Book & Media Reviews, Correspondence, Errata: Letter to the Editor

N95 Respirator Alternatives and Conservation Strategies

Wong, Becky J. MD, MS; Lu, Amy C. MD, MPH; Tarlow, Branden D. MD, PhD; Tompkins, Lucy S. MD, PhD; Chawla, Amanda MHA; Pearl, Ronald G. MD, PhD; Wald, Samuel H. MD, MBA

Author Information
doi: 10.1213/ANE.0000000000005134
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To the Editor

N95 respirator conservation and alternatives. APF indicates assigned protection factor; FFR, filtering facepiece respirator; MRI, magnetic resonance imaging; PAPR, powered air purifying respirator.

We read with great interest the article by Abd-Elsayed and Karri,1 which highlights an important issue facing all health care workers (HCW). Anesthesia providers are especially vulnerable to shortages of personal protective equipment (PPE) as the American Society of Anesthesiologists (ASA) recommends appropriate PPE during all aerosol-generating procedures when working near the airway, such as endotracheal intubation.2 To use optimal equipment,1 the HCW must have knowledge of the advantages and disadvantages of the available options. We provide a summary for the conservation of N95 respirators and their alternatives (Figure).


Surgical N95

Conventionally known as medical N95s, these respirators require fit testing and are fluid resistant and rated in the removal of particulate matter. Historically, filtering facepiece respirators (FFRs) were considered single use, but in the pandemic context, the Food and Drug Administration (FDA) issued Emergency Use Authorizations (EUAs) for the decontamination of respirators. New N95 respirators remain the first choice before a decontaminated respirator.3

Industrial N95

Although industrial N95 respirators require fit testing and are not fluid resistant rated, HCWs are now turning to industrial N95s as a PPE option with the surgical N95 shortage. A full face shield can be worn over the industrial N95 to prevent fluid penetration.

Elastomeric Respirator

Elastomeric respirators are designed to be reusable and require fit testing. They have disposable and replaceable filters, inhalation/exhalation valves, and come in half facepiece and full facepiece masks. These elastomeric respirators are certified to provide protection equivalent or greater than N95 FFRs. Elastomeric respirators do not filter exhaled breaths. Elastomeric respirators are required to be cleaned and disinfected between users. Cleaning refers to the removal of soil from surfaces (eg, cosmetics and skin oils) using water and detergent. Disinfection eliminates all pathogenic microorganisms with liquid chemicals.4 Filters need to be replaced based on the biological agent to be filtered, the manufacturer guidelines, and the infection control policies of the hospital. In the era of universal masking, a procedure mask may be worn over the exhalation valve.


Powered air purifying respirators (PAPRs) provide filtered, positive airflow to the wearer. PAPRs have the motor and blower unit on a belt with a large hose connecting to the head piece. This can be cumbersome and potentially dangerous for a disconnect. MAXAIR (Maxair Systems, Irvine, CA) Controlled Air Purifying Respirators (CAPRs) are a proprietary form of PAPRs which rearranges the blower and motor unit to the head piece with only a thin cord connecting the headpiece to the belt with the battery pack. The Occupational Safety and Health Administration (OSHA) gives an assigned protection factor (APF) to respirators. PAPRs have the benefit of higher APF than N95 respirators, but they are limited by availability, contraindication to magnetic resonance imaging suite due to ferromagnetic parts, and present debatable concerns for exhaust air flow around sterile fields.5


N95 Extended Use Versus Limited Reuse

Extended use of an N95 respirator is defined as wearing the same N95 respirator for repeated encounters with several patients, without removing the respirator between encounters. Per the Centers for Disease Control and Prevention (CDC), the maximum recommended period of use when practicing extended use is 8–12 hours.3

Limited reuse of an N95 respirator is defined as wearing the same N95 respirator for multiple encounters with patients and donning and doffing it in between encounters. The CDC suggests up to 5 uses to ensure an adequate safety margin.6 Furthermore, the HCW should check the respirator for tears, strap breakage, and nosepiece fractures. HCWs should perform their own seal test with each donning and evaluate for increased breathing difficulties. Any of these signs may prompt the user to discard the respirator. A potential model for reuse is a 4- to 5-day cycle of 4–5 respirators in which the HCW wears a different respirator each day. Individual respirators are stored separately in their own paper bag at the end of the day. The HCW should don the next respirator in order of least recently used.

Reprocessed Surgical N95

Reprocessed N95s have been through a decontamination process. Under the FDA EUA, Battelle Critical Care Decontamination System (Battelle, Columbus, OH) was 1 process approved to decontaminate N95 respirators.2 Approved N95 respirators are delivered to the decontamination site for a 4- to 8-hour process: respirators are hung in a closed space, gased with hydrogen peroxide (H2O2) vapor, and left for a clearance phase during which H2O2 is converted to oxygen and water vapor. The decontaminated N95 respirators can be returned to the individual person “index user” or to a general pool of reprocessed respirators. Respirators should be marked after each decontamination cycle and disposed of after the maximum reprocessed number has been reached. The maximum number of cycles is a function of the specific decontamination protocol and type of respirator. An important distinction is that N95s are not cleaned. Cosmetic stains, blood contamination, and soiling on the respirator necessitate disposal, not decontamination. The respirators are quality checked and discarded for any visual markings.

Cleaning and Disinfecting Elastomeric Respirators

Little guidance exists regarding the frequency of cleaning and disinfecting and whether these tasks should be centralized or performed by the individual user. OSHA guidelines for cleaning elastomeric respirators involve removing filters, disassembling facepieces, immersing in detergent, scrubbing, submerging in chlorine or iodine disinfectant agent, rinsing, drying, and reassembling.4 This process would place a high time burden on individual HCWs. The alternative is to have the hospital batch clean and disinfect all elastomeric respirators. This poses an additional workload to sterile processing and incurs extra cost to purchase enough elastomeric respirators to be in circulation.

Hospitals may need to utilize a multipronged strategy to ensure an adequate PPE supply. The options presented here may have varying levels of success based on the hospital size, resources, and capacity for testing patients. However, one thing is universal: the utmost importance for HCWs to be protected.


The authors would like to acknowledge the members of the Stanford N95 Conservation Taskforce, staff, and health care workers from Stanford Health Care for their contributions.

Becky J. Wong, MD, MS
Amy C. Lu, MD, MPH
Branden D. Tarlow, MD, PhD
Lucy S. Tompkins, MD, PhD
Amanda Chawla, MHA
Ronald G. Pearl, MD, PhD
Samuel H. Wald, MD, MBA
Department of Anesthesiology, Perioperative, and Pain Medicine
Stanford University School of Medicine
Stanford, California
[email protected]


1. Abd-Elsayed A, Karri J. Utility of substandard face mask options for health care workers during the COVID-19 pandemic. Anesth Analg. 2020;131:4–6.
2. American Society of Anesthesiologists. COVID-19 FAQs. June 10, 2020. Available at: Accessed July 4, 2020.
3. US Food & Drug Administration. N95 Respirators, Surgical Masks, and Face Masks. June 7, 2020. Available at: Accessed July 1, 2020.
4. Liverman C, Yost O, Rogers B; National Academies of Sciences, Engineering, and Medicine; Health and Medicine Division; Board on Health Sciences Policy; Committee on the Use of Elastomeric Respirators in Health Care. Reusable Elastomeric Respirators in Health Care: Considerations for Routine and Surge Use. 2018. Washington, DC: National Academies Press (US); Available at: Accessed July 3, 2020.
5. Board on Health Sciences Policy; Institute of Medicine. The Use and Effectiveness of Powered Air Purifying Respirators in Health Care: Workshop Summary. 2015. Washington, DC: National Academies Press (US); Available at: Accessed July 4, 2020.
6. Centers for Disease Control and Prevention. Recommended Guidance for Extended Use and Limited Reuse of N95 Filtering Facepiece Respirators in Healthcare Settings: Respirator Reuse Recommendations. Available at: Accessed July 1, 2020.
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