How Effective Are Different Types of Masks?

The World Health Organization tells us that COVID-19 is spread via particles from an infected person’s mouth and nose, emitted when they do things that expel air like coughing, sneezing, or even just talking. Many people initially focused on the very small size of the virus itself (about .1 micron) and worried that masks wouldn’t filter out such tiny bits. But it’s important to remember that people don’t just sneeze out virus particles. The particles hitch a ride on other substances.

It’s an unsavory fact of being human that while we’re talking, singing, coughing, etc., we’re actually shooting out liquid droplets. While the droplets are small enough that we don’t generally notice, they’re much larger than the virus itself and they can contain the virus.

It’s possible to come directly into contact with a larger infected droplet that measures around 100 microns or smaller—for example from someone sneezing near you. But droplets can also be aerosolized into a form that measures around 1 micron—for example when someone coughs into the open air or talks for a time in a poorly ventilated room. These aerosolized droplets can hang around in the air for hours waiting for an unmasked or improperly masked person to breathe them in. But a properly worn mask can protect the wearer by filtering airborne droplets before they enter the lungs and they can protect others by preventing expelled droplets from getting into the air in the first place.

Since we know that N95 masks are designed to filter particles down to about .3 microns, disposable N95 respirators are the obvious frontrunner in terms of protection. But what about other types of face coverings? The new study took the time to test a variety of masks using a cough aerosol simulator that put out droplets from 0 to 7 microns in size. They looked at different types and thicknesses of masks and measured how many particles were able to travel through and around them.

N95 respirators scored about as expected at the head of the pack, scoring even better than their promised 95% (hence the 95 in the name). Double-layer folded polyester neck gaiters and medical procedure masks are essentially tied for second place at around 60% effectiveness, with 3-ply cloth masks and single-layer gaiters taking a close third at around 50%. Unsurprisingly, a face shield alone yields almost no protection at all at 2% and might best be used along with a mask as add-on protection against liquid spatter.

Obviously, this is valuable information and it can help you determine what kind of masks your employees need on the job. But it’s important to consider the study’s real-world applications as well.

1. Proper Mask Fitting and Wear – keep in mind that this study looked at masks that were properly fitted. An incorrectly fitted or sloppily worn mask may be worse than no mask at all as it may cause the wearer to skimp on other factors like social distancing. Be sure everyone understands how to properly wear their mask.
2. Mask Removal – remember that if a mask is preventing respiratory droplets from getting into the air or into the lungs, that means those potentially infectious droplets are on the mask. It’s important for employees to remember that they should remove masks by the ear loops or head straps without touching the mask shell or surface and wash their hands both before and after they use a mask.
3. The Other 40 to 50% – most of these face coverings scored well, but none of them made it to 100%. This makes it vital to impress upon your employees that, even masked, they still need to social distance and take any other necessary precautions. In addition, it demonstrates that measures to change your HVAC air mix, provide good ventilation, etc. are as vital as ever.
4. Work Environment – be sure to take your work environment into account when you choose a mask. If workers are too hot or uncomfortable in their mask, they’ll be tempted to pull it down to cool off.