Some principles of air filtration explained:
- Air filters are usually some form of a fabric style mesh, where the size of the largest openings will determine what gets through.
- The rating scale for air filters as defined by the EPA is here.
- As the opening sizes get smaller, you create more air drag, meaning you need to spend more energy to suck or push the air through the filter.
- Even the smallest pore sizes do not handle all the pathogens. SARS CoV-2 can be as small as 0.07 to 0.09 micrometer, but even a MERV 16 filter has just 75% efficiency in the 0.3 – 1.0 micrometer range. Airdrag is very strong with such a fine filter, and filters tend to need replacement very often.
- Any traditional air filter does load up, and typically at about 1/3 of its service life it starts becoming less efficient and create more and more air drag.
- In some clean rooms and similar facilities HEPA filters need replacement every 10 days.
Dexwet Filters are complementary
Dexwet Pure Air Filters provide and entirely new principle of air filtration, tuirbulence and absorption. Dexwet is strong where traditional air filters are weak, and therefore Dexwet can extend the service life of filters and improve air quality at the same time.
- Dexwet Pure Air is a rigid structure that creates air turbulence as air passes through.
- Dexwet Absorber Fluid is used to coat the filter elements with a liquid that has extremely low surface tension and simply snaps up every particle that comes in touch with it.
- Because of the sorting effect created by the van der Waals effect, particles get sorted form smallest on up and the smallest one get absorbed first.
- The winning formula is to use a Dexwet filter as a prefilter to a traditional filter and this combination can last fare longer than the traditional filter meaning reduced service intervals and less waste.
- In clean rooms, HEPA filters often need changing every 10 days, but with a Dexwet Pure Air, that can be extended to as much as 40-120 days, depending on what level of airquality is needed.
Real Life Performance versus Test Performance
Passing a test one time in a laboratory is one thing. What matters in the real world is something else. Any cloth type filter will catch particles above the opening sizes, but then it loads up and more and more energy is needed to push the air through the filter. In other words, the filter will consume more and more energy over time. What matters is real-life performance.
Problem 1 – Shredding: Particles Pushing Through
The first problem is shredding where the increasing air pressure pushes particles through the filter gradually and they are released again.
Problem 2 – The Billiard Ball Effect
The problem gets worse over time when the filters are really loaded up, and sometimes a larger particle landing in the filter can knock loose smaller particles which then can come through the filter in a little cloud. It is the reason why HEPA filters last only 10 days in critical applications.
The Upshot: Dexwet Prolongs Service Life
The Dexwet Pure Air Filter as a pre-filter prevents the loading of the filter, and so improves performance and service life. As a post-filter it can deal with shredding and the billiard-ball effect. The absorber fluid in the Dexwet filter permanently absorbs anything that comes in touch with it.
Comment on the van der Waals Principle
The MERV test is for conventional air filters using the Sieve Air Filtration Principle. With a sieve, the size of the holes will determine the size of the particles it catches. E.G., a MERV 1 filter may have sieve sized at PM 8, thus can capture particles greater than PM8 and some smaller but most particles smaller than PM8 will not be captured. As the MERV rating system assumes that if an air filter catches PM1 sized particles, then it would also catch the larger PM 2.5 and PM10 sized particles. As this is not the case for Dexwet Filters, it produces anomalies in the test which result in errors where the standard MERV rating calculation cannot be calculated. Dexwet Filtration principle uses Turbulence and Absorption with physics of Attraction. This new air filtration principle does not adhere to the standards set by the sieve principle, which is similar to why Electrostatic Air Filters, a newer air filtration principle compared to sieve, cannot receive a MERV rating as their sieve size are much greater than PM10. An Electrostatic Air Filter can receive a MERV equivalent rating. Dexwet Filters have a greater effectiveness the smaller the particle as per the Van der Waal force principle.