A timely review of the N-95 mask, titled “The N-95 mask: Invaluable ally in the battle against the COVID-19 pandemic” and published in the peer-reviewed medical journal Lung India on behalf of the Indian Chest Society, contains useful pointers for health-care workers (HCW) hampered by the acute scarcity of this life-saving mask. The authors of the paper, Dr Zarir Udwadia and Dr Reyma Sara Raju, describe the N-95 as “the single most important part of the armour” against COVID-19 and say that its shortage has contributed to the deaths of some of the 600 HCWs worldwide.
The paper looks at the special advantages of the N-95 mask, describes how to get a perfect fit to assure safety, and most importantly, reviews recent literature that prolongs the life of the mask.
N-95 masks, which were earlier available freely, are now in short supply. In normal times, 10 million N-95 masks were manufactured every day in China. After the pandemic, this has been stepped up to 116 million but this, too, is inadequate, says the paper, quoting figures from China’s National Development and Reform Commission.
Advantages
Describing the advantages of the N-95, the authors say that unlike the surgical mask, which provides one-way protection to those around the wearer, the N-95 works in a bi-directional way, protecting both the wearer and others around him/her. It also reduces the amount of aerosols that are inhaled. Indeed, it is so-called because “it can remove 95% of all particles with a diameter >0.3 µm, and it is comparable to a Filtering Face piece Respirator2 (FFP 2) mask. A properly fitted N-95 will block 95% of aerosolised particles, down to three-tenths of a micron in diameter, from reaching the wearer’s face. In contrast, surgical masks, designed to protect patients from a surgeon’s respiratory droplets, are not effective at blocking particles smaller than 100 µ. COVID-19 particles were found to measure 1–4 µ in diameter, according to an air sampling study where 245 surface samples were collected from 30 isolation rooms at the National Centre for Infectious Diseases, Singapore, where patients with SARS-CoV-2 were being managed…As we now know, the SARS-CoV-2 is carried by both droplets and aerosols, and hence, an N-95 is essential for the protection of HCWs exposed to these patients.”
Methods of decontamination
Because of shortages of N-95 masks in almost all hospitals, every attempt to prolong their life and use without compromising safety should be explored. The paper looks at three measures which would be commonly available in most hospitals. But it also warns that “decontamination and reuse are not recommended as the standard of care but may be considered at times of crisis.” In fact, “extended use is preferred over reuse as it involves less risk of contact transmission”. The three most promising decontamination methods are: ultraviolet germicidal irradiation, vaporised hydrogen peroxide, and moist heat (60 °C and 80 per cent relative humidity).
The authors say that the current techniques of disinfecting the N-95 mask should, in fact, be avoided. “Currently, what is being used in some centres due to shortages, but cannot be recommended, is the use of ethylene oxide (EtO) and autoclaving. While EtO does not compromise the filtration efficacy, it may be carcinogenic and teratogenic and hence is not recommended. Autoclaving and the use of disinfectant wipes are not recommended as they may alter respirator performance.”
Giving examples of just how valuable the masks are, the paper relates how high demand made some manufacturers cut corners. “Recent tests performed by National Institute for Occupational Safety and Health on a batch of 67 different imported masks found that as many as 60% did not meet standards. Some filtered out as few as 35% of particles only, far short of the 95% it advertised. Many were found to have ear loops to secure them to the head instead of the headbands, which are essential to ensure a tighter fit.”
And another: “In an incident that hinted of ‘modern piracy’ a consignment of 200,000 N-95 masks meant for Germany was diverted to the U.S. as they were being transferred between planes in Thailand.”
And finally, the authors quote Michael Schulman of The New Yorker, who said: “In the pandemic economy, face masks are like bars of gold. Hoarders are hoarding them. Governors are bartering for them. Hospital workers desperately need them.”
