The standard is the EPA Air Quality Index, AQI, also known as Aircompare. The scale is easy enough to understand – it is a measurement of the level of particulates in the air:
- 0 -50 Good
- 51 – 100 Modertate
- 101 – 150 Unhealthy for sensitive people
- 151 – 200 Unhealthy
- 201 – 300 Very Unhealthy
- 301 – 500 Hazardous
The key issues for healthy air are sufficient oxygen and low particulates in the air.
With SARS CoV-2, the issue of particulates has become more important again, for the main avenue of propagation is free-floating aerosols and also via hitch-hiking on particulates in the air. This is why the fastest spread was in areas with the worst air pollution.
Infamously, indoor air is often worse than outdoor air, and while ventilation is clearly necessary for oxygen supply, there is a limit to that approach, because of heating and cooling. Cleaning up the particulates is of paramount importance. Much can be done with active air filtration, but no system is perfect. We provide numerous solutions, including de-stratification fans that produce energy savings and have anti-microbial capabilities, but the real solution is a passive solution, that is provided by the Dexwet Pure Air air filter, which can be retrofit in many instances and used as a pre- or post filter to existing filters.
The Physics of Filters
Legacy filters all consist of some kind of woven or non-woven, but cloth-like material in which it is the size of the openings that defines the smallest particles that get through, and this is measured with the ASHRAE MERV rating. Note that obviously, like a sieve, the finer the filter, the more air-resistance it will create.
By comparison, the Dexwet Pure Air Filter is based on a radically different principle. creates little or no air-resitance. In practice it is usually not even measurable on the intake side, and only about 6% on the return side. Compare that to regular filters which can sometimes produce up to 60% drag.
The air turbulence brings any suspended particles in touch with the filter rods, which are coated with the absorber liquid, which has extremely low surface tensioin. As the rods absorb more particles, the surface expands, increasing the effectiveness of the filter. The filter can ideally be used as a pre- or post filter to existing filters and extend service life as much as 4x to 12x, depending on the application.