As recommended by scientists and the CDC, we need to understand our options in choosing the right mask. Surprise! If you are not a healthcare worker, you do have a lot of options. Some masks are more protective than others. Choose the most protective mask that fits, that you are comfortable with, and it should give you a good seal without any gaps.
We know that our culture is rife with misinformation that puts us in danger. It is imperative that we find information that can be trusted. MaskTogetherAmerica invited experts to share their advice on mask-use.
Omicron is highly spreadable. It can escape immunity from previous infections and vaccination. Their tiny aerosolized particles slip through even tightly woven fabric. Experts made their recommendations based on the fit, seal, material, testing and credibility of the companies. Facemasks are essential source control devices to reduce the expulsion of respiratory aerosols from infected people— that’s why experts recommend choosing masks that have been tested for Aerosol Filtration Efficiency.
Any mask is better than none, but it’s time to get the needed protection against airborne transmission of COVID-19. A loose-fitting homemade cloth mask won’t protect anyone from an airborne virus. Tightening and layering add some more protection. Pairing a tight-fitting mask made of densely woven fabric with a 3-ply FDA-approved surgical mask is a minimal option.
Face masks and respirators are subject to specific standards and regulations. Surgical masks approved by FDA meet the standards of the American Society for Testing and Materials (ASTM). A mask that meets an expected level of source control performance would be stamped F3502 -21. Surgical masks made for medical procedures are defined in ASTM F2100.
The materials used to make a medical surgical mask are tested for their performance in 5 different areas: resistance to fluid, breathability, bacterial filtration efficiency (BFE), particulate filtration efficiency (PFE), and flammability. Surgical masks are rated by their level of barrier efficiency, based on their test marks. The highest level is 3.
The New NIOSH source control performance recommendations was specifically set to prevent the spread of COVID-19 in the workplace. To be accredited by NIOSH, a mask must conform to all criteria stated in the ASTM standard on filtration and breathability, and passes the leakage test, which shows how well it fits and seals on a human face.
Nicolas Smit, an engineer and a recognized expert in Filtering Facepiece Respirators (FFR), does not recommend reusing surgical masks. “Surgical masks should not be reused. The public are not trained on reusing disposable masks. Degraded surgical masks could put people at risk.”
High filtration masks, such as an elastomeric respirator, or a NIOSH-approved N95, or a KF94 mask made in Korea, are rigorously inspected for their filtration efficiency. Some KN95s that are made in the U.S. or imported from other countries have also received FDA’s approval.
Laboratory certified N95s, KF94s and KN95s are made with dielectric microfibers that maintain a surface charge to trap tiny particles. N95s always have head straps while KF94s and KN95s have ear loops. If you ever see something labeled an N95 and it uses ear loops, it’s counterfeit. The straps, the nose clamp and shape of each mask are designed to create a tight seal so the air flows through the filter without leakage. A disposable respirator can only be reused with proper care. In healthcare settings, the CDC have stopped recommending reusing disposable respirators as of May 2021, since we now have adequate domestic supply of respirators approved by the CDC and National Institute for Occupational Safety and Health (NIOSH). Elastomeric respirators can be reused 1000 times. New elastomeric respirators, without an exhalation valve, can be used in the operating room.
Smit strongly objected to reusing disposable respirators. “KN95s and N95s are disposable. They could be reused once or twice but even that could damage the masks. Wearers could be mistaken that they’re protected.”
Smit pointed out that valved respirators are viable options. Respirators with exhalation valves offer comfort and excellent protection for wearers, that’s why firefighters, police, HCWs and others wear them. As source control, NIOSH's studies and CDC's guidelines for healthcare workers confirmed that even without covering the valves, N95 respirators with exhalation valves provide the same or better source control than surgical masks, procedure masks, cloth masks or fabric coverings. Additionally, a valve can be taped from the inside with an electrocardiogram pad or surgical tape to stop emission of unfiltered air particles to provide source control similar to respirators without valves.
Smit also recommends using a mask brace over a level-3 disposable surgical mask. Some of the FDA-listed surgical masks are constructed with polypropylene to block 99.2% of bacteria and particles less than 0.3 microns. A mask brace made of rubber applies light pressure over the nose and cheeks to prevent air from leaking around the edges of the surgical mask. Without leakage, a level 3 surgical mask provides respiratory protection similar to an N95.
The new elastomeric respirators that don’t have exhalation valves is Smit’s strongest recommendation for source control. Smit noted that all elastomeric respirators, half face or full face, offer the highest level of protection for the wearer and people around the wearer. They are equipped with replaceable filter cartridges or flexible, disc or pancake-style filters. A P100 filter can reach beyond 99.997% filtration efficiency. The tight-fitting respirator, made of rubber material, can be reused, disinfected and last for years.
Those elastomeric respirators that included valves can be used by health care workers in a COVID ward or while caring for COVID positive patients or residents without covering the valve since the health care worker would be the one at risk and not the patient. Some don’t cover the valve since CDC's studies show that even uncovered exhalation valves offer better source control than surgical masks.
Nanofiber-based masks and respirators have been reviewed by NCBI. These well-designed masks, washable and reusable, are also recommended by doctors for the general public as a viable option. Electrospun Nanofibers make good filters mostly because of electrostatic interactions with aerosol particles and high moisture resistance. (C&EN Chemical and Engineering News) Nanoengineered functional textiles can block tiny airborne particles as small as .3 micron. Some Nanotech Face Masks that have received N95 certification by NIOSH can filter at least 95% of airborne particles. Some Nanofiber-based masks are disposable, while some are reusable and washable.
