There is a lot of information circulating at the moment both for and against wearing face masks in a bid to stop the spread of Coronavirus. Some countries have made this manditoray for all citizens outside of the house while others have not touched on the matter, or expressed opinions that there is no need to wear them.
So, here are some of the facts relating to Face Masks and their use in tackling COVID-19.
The widely referenced N95 respirators and surgical masks are examples of personal protective equipment used to protect wearers from airborne particles and from liquid contaminating the face.
N95 respirators get their name from their National Institute for Occupational Safety and Health (NIOSH) designation. They contain filter material that uses electrostatic attraction to stops particles of all sizes. The N in the name means the masks are not resistant to oil and the 95 refers to their efficiency. To get a 95 designation, a mask has to filter out at least 95 percent of all particles. Specifically, the designation is granted if the mask proves to filter out at least 95 percent of particles in the size range it is least efficient at filtering out in standard conditions. This is considered “worst case” testing.
In one 2014 study, researchers compared the effectiveness of 44 masks, including N95 equivalent respirators, surgical and dental masks, general cotton masks, and handkerchiefs. They used particle penetration tests similar to those used by NIOSH and the European Union.
They found that the N95 equivalent mask blocked more than 95 percent of all particles, as expected. The surgical mask was around 40 percent effective, with the dental masks coming in at around 60 percent. Cotton masks were around 30 percent effective and cotton handkerchiefs ranged from 2 percent (one layer) to 13 percent (four layers).
Filter efficiency and fit are key for masks, respirators
The best evidence of mask and respirator performance starts with testing filter efficiency and then evaluating fit (facepiece leakage). Filter efficiency must be measured first. If the filter is inefficient, then fit will be a measure of filter efficiency only and not what is being leaked around the facepiece.
Fit should be a measure of how well the mask or respirator prevents leakage around the facepiece, as noted earlier. Panels of representative human subjects reveal more about fit than tests on a few individuals or mannequins.
Quantitative fit tests that measure concentrations inside and outside of the facepiece are more discriminating than qualitative ones that rely on taste or odor.
Mask, N95 respirator filtering performance
Following a recommendation that cloth masks be explored for use in healthcare settings during the pandemic, The National Institute for Occupational Safety and Health (NIOSH) conducted a study of the filter performance on clothing materials and articles, including commercial cloth masks marketed for air pollution and allergens, sweatshirts, t-shirts, and scarfs.
Filter efficiency was measured across a wide range of small particle sizes (0.02 to 1 µm) at 33 and 99 L/min. N95 respirators had efficiencies greater than 95% (as expected). For the entire range of particles tested, t-shirts had 10% efficiency, scarves 10% to 20%, cloth masks 10% to 30%, sweatshirts 20% to 40%, and towels 40%. All of the cloth masks and materials had near zero efficiency at 0.3 µm, a particle size that easily penetrates into the lungs.
Another study evaluated 44 masks, respirators, and other materials with similar methods and small aerosols (0.08 and 0.22 µm).5 N95 FFR filter efficiency was greater than 95%. Medical masks exhibited 55% efficiency, general masks 38% and handkerchiefs 2% (one layer) to 13% (four layers).
These studies demonstrate that cloth or homemade masks will have very low filter efficiency (2% to 38%). Medical masks are made from a wide range of materials, and studies have found a wide range of filter efficiency (2% to 98%), with most exhibiting 30% to 50% efficiency.
Mask and respirator fit
Regulators have not developed guidelines for cloth or surgical mask fit. N95 FFRs must achieve a fit factor (outside divided by inside concentration) of at least 100, which means that the facepiece must lower the outside concentration by 99%, according to the OSHA respiratory protection standard. When fit is measured on a mask with inefficient filters, it is really a measure of the collection of particles by the filter plus how well the mask prevents particles from leaking around the facepiece.
Several studies have measured the fit of masks made of cloth and other homemade materials. We have not used their results to evaluate mask performance, because none measured filter efficiency or included respirators as positive controls.
One study of surgical masks showing relatively high efficiencies of 70% to 95% using NIOSH test methods measured total mask efficiencies (filter plus facepiece) of 67% to 90%. These results illustrate that surgical masks, even with relatively efficient filters, do not fit well against the face.
In sum, cloth masks exhibit very low filter efficiency. Thus, even masks that fit well against the face will not prevent inhalation of small particles by the wearer or emission of small particles from the wearer.
One study of surgical mask fit described above suggests that poor fit can be somewhat offset by good filter collection, but will not approach the level of protection offered by a respirator. The problem is, however, that many surgical masks have very poor filter performance. Surgical masks are not evaluated using worst-case filter tests, so there is no way to know which ones offer better filter.
Certification of KN95 masks
There are many suppliers currently offering respirator masks on the market.
Certification is very important to ensure the mask you are wearing is protecting you.
The two main standards relating to respirator masks are:
USA - the standard is N95 per the NIOSH
European Union - the standard is FFP2 per EN149:2001+A1:2009
The KN95 mask supplied by Hugh Jordan is manufactured and certified to the European standard for respiratory masks FFP2 under EN149:2001+A1:2009
At Hugh Jordan we now have limited stock available of KN95 Face Masks. Shop online now or call us today to place an order.