Air Testing and Purification

How Air filters are rated (CADR, CCM vs HEPA).  This article essentially explains why the traditional rating system is not helpful and why HEPA filtration is important. 2nd Article.

As with water filters, there are several technologies that get used in air filtration:

1. HEPA - pleated random fiber "paper" that captures particles

   • HEPA filters vary wildly in effectiveness depending on the tightness of the ​pores and how tightly sealed the filter is within its unit. Some can filter down below the micron level, some just catch larger dust particles. 

   • HEPA language is not standardized and the various terms don't necessarily mean any standard has been met

   • Generally HEPA is for catching particles above a certain size (whatever the particular filter is built for)

   • They don't catch airborne chemicals (VOC's)

2. Activated carbon - binds charged molecules (including VOC chemical gasses)

3. Charge capture plates - metal plates magnetized by charging with electric current - particles with opposite charge will cling to plates (until they are saturated).  Usually generate ozone.  Can miss lots of particles. 

4. Ionization - most create ozone - which does kill things, but will also damage lung cells if concentrations are high enough to smell the ozone.  I generally do not recommend these due to risk of respiratory irritation or damage. 

5. I like these articles online; they do a good job of explaining the different types of filter technology, what each is good for and where each falls short. (Note that these links are to companies that sell filters)

   1. https://www.airpurifiers.com/pages/hepa-is-key-for-air-purifiers​

   2. https://www.airpurifiers.com/pages/air-purifiers-activated-carbon-technology

   3. https://molekule.com/blog/best-air-purifier-for-volatile-organic-compounds-vocs/

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