In the quest to produce the finest pet odor air filter of all time we at Purrified Air have learned a lot about household air filtration in general. Here is an article we recently published on medium.com on the subject.
I would wager there are at least 100 household air filters on the market, perhaps many more than that. They employ perhaps more than a dozen technologies. Each goes after different impurities, and with different success rates. The casual consumer is at a disadvantage as manufacturers often claim their use of Technology A is highly effective against Impurity Z, when a basic understanding of the implementation of said technology would indicate otherwise. This article intends to provide an overview of the best kinds of air purification and how they work.
For example, if the issue a cat litter box and its urine (ammonia) and feces (hydrogen sulfide) odor, an air purifier designed for dust, pollen and allergies is not going to solve the problem, and vice versa.
There are two general groups of impurities filters seek to remove: particles and odor. When we speak of particles, on the large end we are referring to dust, pet dander and dust mites, and on the small end, soot from smoke, mold spores, pollen and large bacteria cells. Odor (Volatile Organic Compounds, or VOCs), on the other hand, consist of much smaller molecules.
The below table is intended to provide a quick rundown on how the eight main methods being used today work, and how well.
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Type
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VOCs
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PARTICLES
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HEPA (High Efficiency Particulate Air)
Designed in the 1940s to protect Manhattan Project workers from radioactive particles. Captures 99.97 percent of all particles 0.3 microns and larger.
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Not effective
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Includes pathogens, dust, pet dander, allergens, microbial spores, mold spores, smoke, and large bacteria.
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Activated Carbon Is charcoal “activated” through a process of oxygen impregnation which opens a huge amount of microscopic gaps of various sizes, vastly increasing its surface area. These gaps attract odor molecules into matching-sized spaces through a kind of magnetic-like process called adsorbtion (as distinct from absorption). One pound contains 60-150 acres of surface area. The key to successful activated carbon filtration is two-fold. One, there must be enough carbon to last for a given period. Ideally six or more months. A foam pad impregnated with a few grams of activated carbon will only last a short time. Two, contaminated air must be forced through a thick-enough bed of carbon with a fan and produce sufficient “dwell time” for all air to come in contact with carbon. If the fan is too weak, not enough air will become "scrubbed." If too strong, the odoriferous air will blow through before it can become scrubbed.
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Effectively removes VOCs, ozone odor, carcinogens, toxic chemicals and gasses in cleaning products, virus, bacteria and mold if a sufficient quantity and forced air is used.
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Generally not effective. Can capture some extremely small particles such as diesel soot.
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Zeolite works similarly to activated carbon except only for certain VOCs. They include ammonia and hydrogen sulfide, the odoriferous chemicals in urine and feces.
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Effective against ammonia and hydrogen sulfide.
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Not effective.
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Ozone in sufficiently large quantities is effective against odor but dangerous to breathe. One common use is in the cleaning of odor in hotel rooms between guests, or in homes that have been vacated while ozone generators are operating.
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Effective against VOCs.
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Not effective.
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Ultra Violet (UV) is good for airborne microorganisms such as bacteria and viruses.
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Not Effective VOCs.
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Not Effective against particles.
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PCO (Photocatalytic Oxidation) shines UV light onto a surface coated with titanium dioxide (TiO2). This catalyzes hydroxyl radicals and super-oxide ions that “burn” VOCs and micro organisms down to .001 microns in size.
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Effective against VOCs and micro organisms such as bacteria, viruses and mold spores.
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Not Effective.
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Ionic Filtration generates negatively-charged ions. In the air, they attach to contaminants, which have a positive charge in the air. They are weighed down and fall to the floor, leaving them there to be cleaned up or picked up by moving air. This method is considered inefficient as even with a fan, the generated negative ions may not move beyond about six feet from the generator, leaving all other air untreated.
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Works somewhat but not effective.
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Works somewhat but not effective.
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Catechin is the new old kid on the block. Catechin filters get their name from a naturally occurring bioflavonoid found in green tea that has been used in traditional medicine since ancient times. Catechin — which has antiviral and antibacterial properties — is typically infused into the dust prefilter, which enables it to strip the passing air of odor-causing pollutants such as tobacco smoke and pet smells. An equally important benefit is that they trap and deactivate microscopic bacteria and viruses, which can diminish or prevent the spread of some diseases.
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Effective against VOCs.
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Not effective against particulate matter by itself, but usually combined with dust pre-filter.
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It is my hope that you will come away from this article ready to evaluate household air filtration products you find on the market and match them with your needs.
Sources:
https://www.modernalchemyair.com/technology
http://web.mit.edu/parmstr/Public/hvac/compressor/Mitsubishi/catechin_07.pdf
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