Buying a Pet Air Purifier

pet air purifier

Pet allergies are triggered by proteins in the animal’s

  • saliva
  • urine
  • skin

The proteins are the allergens – the actual components that trigger an allergy. Not the saliva. Not the urine. Not the skin. The proteins inside these substances are the allergens which trigger allergic reactions.

The proteins become airborne – that is to say these proteins become airborne allergens – only after the substance around the protein dries.

With saliva, the protein is first transferred from the animal’s mouth (primarily tongue) to its fur - proteins from saliva stick to fur when the animal licks itself. The saliva then dries on the fur.

Note – the fur is NOT the trigger – the protein from the saliva that stuck to the fur, dried up and then became airborne is the trigger. This means that a short haired or even hairless animal that doesn’t shed can produce just as many allergens from saliva as a long-haired animal that sheds.

With urine, the liquid portion of the substance simply has to dry up for the protein that remains to be able to become airborne.

With skin, the skin cell dries up and flakes off and this is what allows the protein component to be able to become airborne.

Particle Size

The airborne proteins are extremely small. Fel d 1, the most common cat allergen is microscopic – somewhere around 0.0025 microns in size.

Their small size in addition to their “jagged” shape allows the proteins to stick to a wide variety of different surfaces and, as it relates to air purifiers, other particles (both airborne and on surfaces) at a wide variety of different sizes.

To explore this further, let’s again use Fel d 1 as an example. Studies have shown that the allergen mostly sticks to larger particles. In a particular sample of air, close to half the Fel d 1 (49%) was associated with large particles and only about a quarter (23%) of the Fel d 1 in the sample was associated with small particles. The study defines large particles as particles larger than 9 microns and small particles as particles smaller than 4.7 microns. We can assume that the rest of Fel d 1 in the sample was associated with – stuck to – particles between 4.7 and 9 microns in size.  

What are these particles? Any solid particulate that’s in the size range specified above. In the home environment this is usually dust or more specifically, household dust. To see what specific particulates make up dust in the home see here.

Thus the ultimate path of the protein (allergen) is not only from the animal to the air to you but also from the animal to dust to you (when the dust is inhaled).

So, to remove airborne pet allergens you not only have to remove the allergens themselves but also the other particles they may cling to.

Again, in the home, for the most part, these other particles are dust particles. And to eliminate dust particles you have to consider both

  • settled dust and
  • airborne dust

For settled dust, the solution is simple: Wipe it off the surface - with a mop or duster – or suck it off of the surface – with a vacuum.

For airborne dust, the solution is an air purifier or more specifically, an air purifier equipped with a HEPA filter.

HEPA filter for particles

HEPA filters are able to capture all airborne particles – no matter what their size. This means that a HEPA equipped air purifier will be able to remove both airborne allergens themselves and the particles they associate with – namely dust.

The best HEPA equipped air purifier currently on the market, according to our testing, is the Winix 5500-2.

Pre-filter for larger particles

The pre-filter is important because it’s going to save the HEPA filter from “saturating” with particles quickly. Larger particles like pet fur will collect on the pre-filter. This leaves the HEPA filter with only the smaller particles to have to filter out of the air.

The best pre-filters feature a mesh grille that’s washable. A washable pre-filter allows you to wash it every couple of weeks instead of needing to constantly replace it.

The Winix 5500-2 features this exact type of pre-filter.

Carbon filter for odors

Most air purifiers on the market come equipped with a carbon filter for gas filtration. The carbon will remove unwanted gases from the air – such as pet odors. There are two different types of carbon filters that are prominent on the market.

The first type is a fiber based filter that’s simply coated with carbon.

The second type is a pellet based filter that contains actual carbon pellets inside a plastic honeycomb like frame.

The second type is more effective because it provides a greater surface area for gas adsorption.

Again, the Winix 5500-2 is the best option. It is the only air purifier in its price range that comes equipped with a pellet based carbon filter.

Special notes

1. An animal doesn’t need to be present for animal allergens to be present.

Recall the microscopic size of animal allergens (proteins) and how they stick to particles (dust) in the air, particles on surfaces (settled dust), and surfaces in general.

This allows animal allergens to be transferred quite easily from one environment to another – either by the airborne dust, by dust (particles) that have settled on larger objects (like clothing), or by surfaces themselves moving from one environment to another.

This also allows animal allergens to stay in a particular environment long after the animal that originally produced the allergens is removed. In this scenario an air purifier can be used to remove the allergens that have been left behind.

2. Larger, more pets

If you have a lot of pets and/or large pets they’re going to produce more allergens. They’re also going to produce more dust – via dead skin cells. So, take that into account when making your purchase decision.

Normally, we recommend one 250 CFM unit per 300 sq. ft. However, if you have very large animals or many animals we would go as far as halving the square footage recommendation down to one 250 CFM unit per 150 sq. ft. The same recommendation – one 250 CFM unit per 150 sq. ft. – also applies if you are especially sensitive to pet allergens. You can certainly try using only one unit in larger areas up to 300 sq. ft. but if you still show symptoms consider adding a second 250 CFM unit so that you have two 250 CFM units for 300 sq. ft.

3. Applicable to all pets

It doesn’t matter if you have a cat, dog, guinea pig, or rabbit – all these animals release allergens in the form of proteins that travel around your home by the methods we described above. To remove these allergens and associated particles from the air you use the same method you use to remove cat and dog allergens – an air purifier equipped with a HEPA filter.

4. Pet dander vs pet allergen

Pet dander is dried pet skin. Anything that’s visible that comes from a pet – most notably the pet’s fur – is often called pet dander however, technically speaking, only the pet’s dried skin is pet dander.

Pet allergens are specific proteins that may or may NOT be in the pet’s dander.

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Comments (1)

Gary Csays...

Thank you for you great site and the practical and reasoned advise.! It has been very helpful.

You comments on the WINIX 5500-2 have been very useful. Beyond just it lower cost, I specifically like the separate pellet washable activated carbon filter. Very seriously thinking about getting it for all the reason you have clearly delineated.

My question: WINIX has a HR900 model which except for a lower CFM has a non-washable pellet carbon filter(Type T filter set) per their online manual vs the washable one that comes with the 5500-2 Type H filter set. WINIX positions the HR900 as a pet model. Both activated carbon filters have a one year rated life.

Does the non-washable filter have any better raw filtering capability then the washable one? If not, it seems the washable one would be more useful. If one noticed an increase in odors, one could attempt to wash it within it rated one year life. The non-washable one would obliviously have to be replaced.

Also, in general, is a washable pellet filter really useful? Or if you can sustain the cost, just plan for an replacement when one noticed increased odors. Bottom line: Is washable useful or just marketing?

Thanks for any comments and advice!