Ideally, a HEPA filter is used to remove the majority of polluted air. HEPA stands for high-efficiency particulate air. A true HEPA filter is one that can trap 99.97 percent of dust particles that are 0.3 microns in diameter. The filter material is able to trap the particles because it is made up of very dense glass fibers. Dust particles either get stuck on impact, interception or diffusion.
HEPA filters were originally developed to clean up radioactive particles in the nuclear industry. Nowadays the filters are commonly found in households. A genuine and certified HEPA filter will guarantee prevention against mold, bacteria and viruses.
To put that in perspective, microparticles that are emitted from car exhaust is usually described as PM10 size or less than 10 microns wide. HEPA filters are therefore the best filters for closed areas.
However, people cannot wear HEPA filters as masks because they need a fan or machine to push air through them to work efficiently.
When it comes to respiratory equipment, NIOSH (the testing agency that certifies filters) recognizes 9 different types based on efficiency. Letters refer to the filter’s resistance to oils. N means not resistant to oil, R is oil resistant, and P is oil proof. The 95 label is tested to prevent against 95% of PM2.5 particles, the 99 label prevents 99% or more, and the 100 labelled masks are efficient against 99.97% of PM2.5 particles.
Active carbon is one of the most porous filter materials and is mostly used in water filters but has recently also been woven into fabrics for respirators. Active carbons can catch as much as 99.99% of particles 0.12 microns and above, about 2 times as small as what a HEPA filter removes.
The questions for some is if the pollution they are encountering is also going to be able to get into their eyes. In a place that has chemicals and toxic vapors floating in the air, a full-face respirator with organic vapor filters is best. This kind of mask should prevent against pesticides, epidemics, chemicals, as well as any particles over 0.3 microns in size.
If pollutants won’t get into the eyes, a respirator with a pair of P100 filters will do well in preventing the breathing of all toxins. A 3M gas mask is less costly than a full-face mask and the filter cartridges can be purchased separately. For different situations, the right cartridges can be used, and P100 filters can also be attached to most half size respirators.
Next in line is a high quality FFP3 certified mask, which means it’s an N99 mask called the 3M Aura 9332+. This is the disposable fabric mask that has high resistance to particles due to the thick microfiber you breathe through when wearing it. It won’t last that long though due to its rather flimsy straps.
Other N99 rated masks are the next best masks which comply with NIOSH ratings to block particles as small as 0.3 microns. There are numerous masks with N99 ratings made by many factories and branded by large or small bra
nds like HoneyWell, 3M or Zelbuck.
Then we go down a level in protection to a respirator that blocks 97% of organic vapors, which drops it down to fit into the N95 rating.
Disposable fabric masks are usually also rated N95, which means they block 95% of PM2.5 particles, but do not resist oils. We have seen more and more affordable options available recently.
Exhalation valves are great to have on a mask because they allow you to breathe out. If you are sick however, do note that your coughs, sneezes or exhales will leave the mask through the valves. We provide masks for hot climates so they need to have valves, and we suggest to remove the mask when you sneeze or cough so your filter does not get contaminated.
Do be careful though that there are manufacturers that do not test their masks but still go ahead and stamp them with the N95, N99 or other labels. We’ve tested the fakes and they tend to only block 60-90% of particles. If you’re hesitating buying a mask because it has such an affordable price, do check the box or papers for its lot code which you can check on the manufacturer’s website for authenticity.