On March 3, 2020, at the beginning of the COVID-19 pandemic, the World Health Organization called for a significant increase in manufacturing of personal protective equipment to meet rising demand and to protect healthcare workers and their patients. WHO estimated that up to 89 million medical masks and 76 million exam gloves were needed each month. In the United States, CDC would soon issue crisis capacity strategies to help address the shortages of N95 respirators and disposable medical exam gloves. These strategies included extended use and reuse of PPE.

Over the next few months, healthcare providers and hospitals around the world were overwhelmed with patients, which strained the global supply chain for PPE. Both N95 respirators and medical exam gloves are critical PPE components for healthcare workers, helping protect against the spread of respiratory diseases to and from patients. N95 respirators are designed to filter small airborne respiratory droplets, including those associated with coughs, sneezes, breathing, and speech, and therefore provide a higher level of protection to healthcare workers than surgical masks and cloth face masks. If used appropriately, disposable medical exam gloves can provide additional protection against the transmission of most airborne viruses, including SARS-CoV-2.

Since PPE supply has returned to normal levels, CDC no longer recommends crisis capacity strategies such as extended use and reuse of PPE. But knowledge about these strategies will help healthcare providers protect their workers and their patients in the event of future shortages.

EXTENDED USE OF N95 RESPIRATORS CDC has continued to update its “Strategies for Optimizing the Supply of N95 Respirators.” This webpage specifies guidelines on the limited reuse of N95 respirators during known shortages and includes the following recommendations for users:

• Consult with the manufacturer regarding the maximum number of reuse and donning activities that can be performed with its N95 respirator. Redonning an N95 respirator could reduce its fit and effectiveness.

• As a default, CDC recommends that N95 respirators not be reused or redonned more than five times. A proper pre-use inspection and user seal check should occur prior to each reuse.

• Protect against contamination by wearing a face shield or face mask over the N95 respirator.

• As a limited reuse strategy, rotate products to reduce the risk of self-contamination between uses. CDC recommends rotating N95 respirators with at least 72-hours storage in a breathable paper bag prior to reuse. This recommendation is based on evidence that the SARS-CoV-2 virus would no longer be viable after this time has elapsed. However, as CDC acknowledges, evidence in the peer-reviewed literature suggests a storage time of seven days may be more appropriate.

• When a shortage exists and rotation is not feasible, seek proper decontamination methods. CDC first recommends consulting the manufacturer or third-party expert organizations or laboratories for information on how to decontaminate the specific N95 respirator without affecting its performance. In the absence of these guidelines, the decontamination strategies recommended by NIOSH include ultraviolet germicidal irradiation, vaporous hydrogen peroxide, and moist heat. This article provides additional details on decontamination of N95 respirators.

SUPPORTING RESEARCH ON N95 RESPIRATORS Since the COVID-19 pandemic started, researchers and experts have worked to address critical gaps in knowledge on extending the use of N95 respirators under crisis conditions. One such group that industrial hygienists and healthcare providers should be aware of is N95DECON, a collective of over one hundred scientists, engineers, clinicians, and professionals from around the world focused on providing stakeholders valuable information on the decontamination and reuse of N95 respirators. The organization’s website provides a repository for peer-reviewed research and technical reports on the subject as well as important considerations regarding a method’s effectiveness, effects on respirator filtration efficiency and fit, available guidance and protocols, associated hazards, and costs. Below is a summary of recent work posted to n95decon.org. Key papers in the peer-reviewed literature are listed in the box below.

N95 Methods Implemented in Hospitals The primary methods used in hospital settings for disinfecting and reuse of N95 respirators include ultraviolet C (UV-C) irradiation within a room or cabinet, vaporized hydrogen peroxide, hydrogen peroxide gas plasma, and heated convection chamber. All these methods are well supported in the peer-reviewed literature and by regulatory guidance.

UV-C irradiation at a peak wavelength of 254 nm and a dose of at least 1.0 Joules per square centimeter (J/cm2) shows significant germicidal effectiveness against SARS-CoV-2 with certain N95 respirators. The dose of UV-C must be delivered uniformly to all surfaces of the respirator, which can be challenging. Significantly higher doses of UV-C may damage the respirator and thus are not recommended. Furthermore, the elastic straps may require additional chemical disinfection. The primary advantages of this method are that it does not affect filter performance or respirator fit and leaves no chemical residue. Therefore, the number of reuses is likely to be limited by fit diminution caused by donning and doffing.

Hydrogen peroxide vapor and gas plasma methods have been shown to effectively inactivate SARS-CoV-2. These methods are specific to tested brands of N95 respirators, and their implementation involves an additional chemical hazard that requires use of trained personnel and adequate facilities. A chemical residue can remain on the respirators, so adequate off-gas time is required to protect users. But compared to other methods, hydrogen peroxide vapor and some gas plasma applications provide a higher level of disinfection and repeated treatments are less likely to affect filtration efficiency and fit.

The use of heat combined with humidity has potential as an inexpensive decontamination treatment, especially for hospitals and other settings where cost and ease of implementation are limiting factors. Evidence suggests that incubation for more than 30 minutes at 70–85 C and greater than 50 percent relative humidity is likely to sufficiently inactivate SARS-CoV-2. In contrast to heat alone, the addition of humid conditions has shown promise with multiple enveloped and non-enveloped viruses, but data are limited for SARS-CoV-2. It is likely this method will not sterilize an N95 respirator and may affect filter efficiency and fit over time. Only validated methods specific to the respirator brand and infectious agent should be used.

N95 Methods Under Investigation Of the several methods currently under investigation, those showing promise include a 2–3-minute microwave-generated steam treatment and a room-temperature treatment with a waiting time of up to seven days for SARS-CoV-2 inactivation. CDC provides guidance on the room-temperature treatment, but supporting evidence in the peer-reviewed literature appears limited at this time.

N95 Methods Not Recommended A number of methods are not recommended, primarily due to their failure to effectively inactivate SARS-CoV-2, issues with compromised filter efficiency or fit, or the presence of a chemical residue or hazard. Some of these methods include submersion in alcohol, bleach, or soapy water. Ethylene oxide and formaldehyde vapor treatments are not recommended primarily for the residual hazard to users. Exposure to sunlight has also been shown to neither effectively decontaminate N95 respirators nor inactivate SARS-CoV-2.

EXTENDED USE OF DISPOSABLE EXAM GLOVES CDC has also continued to update its “Strategies for Optimizing the Supply of Disposable Medical Gloves,” which specifies guidelines on methods for sanitizing gloved hands to extend use of gloves during known shortages. The guidelines include the following recommendations for users:

• Disinfection and extended use of disposable medical exam gloves is not a recommended standard practice and should only be considered during extreme shortages.

• Reuse and repeated donning and doffing of disposable gloves is not recommended, as this could affect the integrity of the gloves. Disinfection should only be performed on gloved hands for the purpose of extended use. Once removed, the gloves should be discarded.

• Before disinfection, gloves need to be inspected and discarded if signs of damage or degradation are present. Signs of damage include tearing or holes. Signs of degradation include tackiness, changes in elasticity such as increased stiffness or softness, discoloration, and cracking.

• Visibly soiled gloves should be discarded.

• Published research shows that up to six repeated disinfection cycles with an alcohol-based hand sanitizer (ABHS) do not significantly affect the mechanical integrity of latex and nitrile gloves. CDC’s webpage “Hand Hygiene in Healthcare Settings” recommends standard guidelines on the use of an ABHS. The agency cites a 2016 paper published in the Journal of Occupational and Environmental Hygiene that reported lower changes in tensile strength for both latex and nitrile gloves resulting from use of an ethanol-based ABHS compared to an isopropanol-based ABHS.

• When an ABHS is not available, soap and water can be used to clean and remove contamination from the gloves for up to ten repeated treatments, as per CDC’s “Hand Hygiene in Healthcare Settings.” Long-cuffed gloves are recommended to prevent soap and water from entering the glove. No supporting literature was cited by CDC on the integrity of latex or nitrile gloves exposed to repeated treatments with soap and water, but a preliminary study recently published on the preprint server medRxiv addresses this subject and is discussed later in this article.

• Based on limited data, an alternative of up to ten repeated disinfection cycles with dilute bleach (for example, a 0.1 percent sodium hypochlorite solution) can be considered. Once again, long-cuffed gloves are recommended to protect the hands inside the gloves. The treatment involves dipping the gloved hands in a dilute bleach solution for five seconds, allowing one minute of contact time in air, then rinsing with water and blotting dry with a paper towel. This treatment is based on a manufacturer’s permeation data for a nitrile glove exposed to a more concentrated 10–13 percent bleach solution. However, it must be noted that permeation is a different process than degradation. The American Journal of Advanced Research recently published a study on the integrity of disposable exam gloves exposed to repeated bleach treatments, which is discussed later in this article.

SUPPORTING RESEARCH ON EXAM GLOVES Several new studies have investigated the physical and mechanical integrity of latex and nitrile gloves repeatedly treated with ABHS, dilute bleach, and soap and water. The two critical factors evaluated in these investigations include:

1. Physical integrity and penetration via holes or tearing, which can be measured using a standardized water leak test. For example, the Acceptable Quality Level (AQL)—a measure of the percentage of defects or of gloves that fail the water leak test—for non-sterile medical exam gloves varies from about 1.0 to 4.0. Significant changes in the gloves' physical integrity during use would be a cause for concern.

2. Mechanical integrity via degradation and changes in the polymer structure, which can be measured as a change in tensile strength, elastic modulus (stiffness), or elongation at break (ductility). These tests can indicate if a glove is likely to fail under conditions of use.

Physical Integrity The medRxiv study “Physical Integrity of Medical Exam Gloves with Repeated Applications of Disinfecting Agents: Evidence for Extended Use” evaluated latex and nitrile exam gloves sourced from the U.S. and India. The researchers found that up to ten applications of a dilute bleach solution had the least impact on physical integrity, as compared to repeated applications of an ABHS or soap and water. However, significant variation was observed, and results were inconclusive. Thus, the authors recommended that specific glove and disinfectant combinations be tested when facing shortages and extended use is necessary.

Mechanical Integrity In addition to the studies cited by CDC in support of their recommendations for ABHS, two recently published studies have evaluated repeated treatments with dilute bleach and soap and water.

A July 2021 publication in the American Journal of Advanced Research found that latex gloves performed well with no significant change in elastic modulus after ten repeated treatments with dilute bleach. In contrast, two of the three nitrile glove brands exhibited significant decreases in elastic modulus of about 50 percent or greater. The general recommendation was to not use dilute bleach treatments with nitrile gloves.

Another publication in the July 2021 American Journal of Advanced Research found that latex gloves performed well with no significant change in elastic modulus beyond 26 percent after up to 20 treatments with soap and water. However, nitrile glove brands exhibited significant changes in elastic modulus in excess of 40 percent after as few as five repeated treatments. In general, soap and water did not appear to be an appropriate disinfection method for nitrile gloves.

Overall, it appears that latex and nitrile exam gloves can be treated up to six times with an ABHS, whereas only latex exam gloves appear suitable for dilute bleach and soap-and-water treatments as outlined in the CDC guidelines. The results of these studies indicate that more research on the effects of water-based disinfectants on the mechanical integrity of nitrile exam gloves is needed. Water absorption alone may be a contributing factor with nitrile gloves.

TAKEAWAYS The extended use and reuse of disposable N95 respirators and medical exam gloves are not a recommended practice. Nevertheless, during the COVID-19 pandemic many authorities endeavored to address shortages of PPE critical for infection control, which included the establishment of guidelines for extended use and reuse of disposable PPE. Several viable methods have been established for N95 respirators. While more research is needed on disposable exam gloves, CDC guidelines appear favorable for extended use and reuse of latex exam gloves. Caution should be applied with nitrile exam gloves, especially when turning to methods other than alcohol-based hand sanitizers. Ethanol-based sanitizers appear to affect glove integrity less than isopropanol-based sanitizers.

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