HEPA Air Filters
HEPA air filters are now the standard in respirator filters. They have been on the market for almost 60 years and are the highest residential and commercial grade air filtration systems on the market. Because the name HEPA goes far in the eyes of consumers, several brands have created knock offs branded to be 99% HEPA, or HEPA type. These are not legitimate claims and they do not meet the standard requirements of real HEPA products. Be wary of look-alikes: they do not provide the same protection.
Legitimate HEPA air filters are constructed to stop airborne particles via three specific methods: interception, impaction, and diffusion. This is done via a sheet made of tiny fiberglass strings, arranged completely and effectively random. Because of the density of the fibres themselves and the quantity the three particle halting methods above work together to clean the air.
The interception method is where the airborne particles actually stick to the strings and cannot get loose. The impact method is mostly utilized when particles weave through the strings and eventually collide with and embed into the strings. The diffusion method causes larger airborne particles to collide with smaller particles that have been slowed or stopped within the filter, which eventually causes them to come to a slow stop inside the filter.
The above are called "methods" but in all reality they are only results of the random arrangement of the fiberglass strings inside the filters. They are meant to remove at least 99.97% of all airborne particles which are 0.3 micrometers in diameter, but they also stop particles in a variety of ranges below and above 0.3 micrometers.
The string density is what makes HEPA air filters high grade, and is also what separates them from look-alikes. A higher quality air filter will have a higher density of strings, which will in effect halt and catch more particles in the air.
It's essential to ensure that a filter is legitimate HEPA-grade if you are looking for real clean air. A low quality air filter will remove several potentially harmful particles, but most can only remove those within specific size groups (0.2 micrometers or 0.3 micrometers, for example). Those with allergies should also be especially sure an air filter is HEPA quality because allergens can come in all sizes. A low-grade filter will not protect from all allergens, and even one type can vary in size.
Ensure that you are getting a real HEPA air filter. Price should not factor into you or your loved ones' respiratory health, and in many cases the difference between a quality and sub-par filter can be noticed with just a few breaths. Don't take a chance with airborne particles.