My 15-year-old kitty is lying on my arm as I type. Yes, I am allergic to him. Yes, I allow him to place his beautiful little head on my arm. My eyes are itching more than normal, but sometimes snuggles are more important than comfort. I know, sometimes I do not act in my own best interest. I know that carpet harbors dust, but it also keeps my feet warm. I know that cat dander causes itchy eyes, but my little guy needs human contact. Rather than stopping my bad habits, I will use technology to overcome them.
For airborne allergens, the best allergy device is a HEPA air purifier. The best air purifier will be the one that not only cleans the air, but also has the sense not to wake us up at night with lights and noise.
Reduce the Allergen Source, and Ventilate the Air, if You Can
I consulted the EPA on its suggestions for cleaning pollutants and allergens from the home. Here is what they said.
Step 1: The first step to improving indoor air is to “reduce or remove the sources of pollutants.”
If, like me, you are keeping your carpeting and your cat, then let us move on to step two.
Step 2: “Ventilate with clean, outdoor air.”
Does sneeze-inducing pollen also fill your outdoor air? OK, let us move on to step three.
Step 3: “Upgrade the air filter in your furnace or central heating.”
So… huh… there is an air filter in my furnace or central heating? Let us Google, shall we?
“The location of your furnace filter is typically located somewhere close to where the fan is located. This applies to all different types of heating furnaces, including gas furnaces, oil furnaces, electric furnaces, as well as air conditioners. Even individuals who have been working in the HVAC industry for a number of years occasionally have difficulty when it comes to locating tricky hidden furnace filters, but they are always there somewhere!”
A whole-house filter is an effective method to control allergens. When you figure out where your furnace filter is, shop here for a replacement that filters allergens.
Step 4: “Portable air cleaners, also known as air purifiers or air sanitizers, are designed to filter the air in a single room or area.”
Do Air Cleaners Even Help Reduce Allergens?
Yes, air cleaners do help reduce allergens. HEPA filter air cleaners perform the best.
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“[S]tudies have shown that portable air cleaners … can reduce some adverse health effects … in sensitive populations such as children, people with asthma and allergies, and the elderly, as well as in healthy individuals.” (EPA, p. 10).
How to Pick a Good Air Cleaner
There are a few rules to picking a good air cleaner. Get a HEPA filter, and a large Clean Air Delivery Rate. Do not get a UV germicide, or an ozone generator. Avoid lights and noise, as these will keep you awake.
Use HEPA Filters to Reduce Allergens
Air cleaners using High-Efficiency Particulate Air (HEPA) filters are more efficient than non-HEPA cleaners. For allergen reduction, always get a HEPA purifier. They get rid of more junk faster.
Use a High CADR for Your Space
CADR is “Clean Air Delivery Rate.” Room volume determines the minimum CADR you need. For instance, if the room you are cleaning is 10 ft. x 10 ft. with an 8 ft. ceiling, then you want a CADR of absolutely no less than 65. If you run the “CADR 65” purifier at full speed, that cleaner will do a reasonable job filtering allergens out of the room. However, that is a minimum level you want. I like to go higher than the minimum CADR. Get a little bit bigger than you need, but then stop. After that, you are using more electricity than you need to use to clean the air for that room.
For every 100 square feet, add 65 CADR. A 200 sf. room requires a minimum of 130 CADR. A 300 sf. room requires a minimum of 195 CADR. Each 100 square feet raises the CADR by 65.
These values are based on 8 ft. ceilings. Do you have 14 ft. ceilings? That is a huge difference, and will knock your CADR’s way up. However, it is easy to figure out. I made you a chart to help you figure out the minimum CADR for your air purifier.
First, get the cubic feet of the room. Multiply the length by the width by the height. A 10 x 10 x 8 ft. room is 800 cubic feet. A 10 x 10 x 14 ft. room is 1,400 cf.
Now look up your cubic feet in this chart to get your minimum CADR. The formula is
cubic feet x .08125 = Minimum CADR
TABLE: Minimum CADR by Room Size Examples
Minimum Air Purifier CADR
8 ft. Ceiling Examples
Room Dimension (cu. ft.)
Minimum CADR Required
10 x 10 x 8 ft. (800 cf.)
10 x 20 x 8 ft. (1,600 cf.)
15 x 20 x 8 ft. (2,400 cf.)
20 x 20 x 8 ft. (3,200 cf.)
20 x 25 x 8 ft. (4,000 cf.)
Minimum Air Purifier CADR
14 ft. Ceiling Examples
Room Dimension (cu. ft.)
Minimum CADR Required
10 x 10 x 14 ft. (1,400)
10 x 20 x 14 ft. (2,800)
15 x 20 x 14 ft. (4,200)
20 x 20 x 14 ft. (5,600)
20 x 25 x 14 ft. (7,000)
Avoid Lights and Noise
We bought an air humidifier a few years ago. We need to get rid of it. It works. That’s not why. It’s just that there is a blue light shining inside the unit that would make a lighthouse jealous.
Two things we learned from our petting zoo of humidifiers: bedroom machines should be dark, and they should be quiet.
One effective strategy to reduce air cleaner noise is to get a unit with a CADR much larger than you need. If you get the minimum CADR, you will need to run the unit full time at the highest speed. A machine with larger CADR can run fewer hours and lower speeds to the same effect. You can run the higher-CADR machine at a lower airflow setting, which will reduce the noise it makes.
If the noise or a light keeps you up, you’ll want to stop using the air cleaner.
Do Not Use Ozone Generators to Clean Air
Ozone generators do not clean the air. The ozone that they produce is terrible for the lungs.
Do Not Use UV Air Purifiers
It sounds great. A light that kills mold and bacteria. While ultraviolet (UV) light can, in fact, kill microorganisms, it’s unlikely the light in an air purifier will kill much of anything. Additionally, the UV-C type of germicidal light produces harmful ozone as a side effect.
“Some UVGI cleaners used in HVAC systems or portable air cleaners are advertised to reduce dust mite allergens, airborne microorganisms (e.g., viruses, bacteria, molds) and their spores, and gaseous pollutants from indoor air. However, it is likely that the effective destruction of airborne viruses and fungal and bacterial spores requires much higher UV exposures than a typical residential UVGI air-cleaning unit provides (Kowalski and Bahnfleth 2000; Scheir and Fencl 1996; VanOsdell and Foarde 2002). No research or studies were found that show UV disinfection is effective in reducing dust mite and mold allergenicity or that UV radiation has the potential to remove gaseous pollutants. Both dead or live fungal particles can cause allergic reactions in sensitive populations. Therefore, UVGI cleaners might not be effective in reducing allergy and asthma symptoms. If mold is growing indoors, it should be removed, and the conditions leading to its growth should be addressed (U.S. EPA 2001). (EPA p. 28)”
Have Reasonable Expectations
Studies have shown a statistically significant allergy health benefit associated with air cleaner use. However, do not expect a portable air cleaner to remove 100% of a room’s allergens.
Commit to Air Cleaner Maintenance
Only get an air purifier if you will be willing to change out the filter down the road. It is not a huge or expensive job.
It’s just that you have to do it to make the air cleaner worth buying in the first place.
Did you know that removing a filter for maintenance could expose you to it dust and debris?
Some air cleaners offer washable filters. Until you wash the crud down the sink, it can get in your face.
I would rather have a replaceable filter than one that I have to wash.
Air Cleaners that Meet these Criteria
I like the Levoit air cleaners, especially the model made for cleaning smoke. It meets all of the criteria we laid out. It uses both a HEPA and a carbon filter. It does not have a useless UV feature, and it does not generate ozone.
You can turn off the LED display so that it does not bother your sleep. It runs only on the lowest setting when in “sleep mode,” to give you the quietest operation. The HEPA filter is not washable; you throw it away and replace it with a fresh one.
Products Mentioned in Allergy Articles
To view all the products mentioned in the articles, go to the Best and Mentioned Air Cleaners and Vacuums article.
Learn more, especially about whether you should buy a certified vacuum cleaner or air purifier. Go to Are Certified Vacuums & Air Cleaners Better for Seniors? Part II
Allergy Article References
- Why Get Certified?, Allergy Standards
- Allergic Diseases in the Elderly, Clinical & Translational Allergy, 2011
- Allergy Capitals Spring 2019, Asthma & Allergy Foundation of America
- US Census McAllen, TX
- US Census Jackson, MS
- US Census Providence, RI
- US Census, Memphis, TN
- US Census, Springfield, MA
- HEPA Filter, US National Library of Medicine, , June 2019
- asthma & allergy friendly® Certification Program
- Asthma Canada
- Allergy Standards Limited
- asthma & allergy friendly®, About the Program
- Allergy Proof Your Home, Mayo Clinic, Sep 6, 2018
- asthma & allergy friendly® Certification Standards
- Air ions and respiratory function outcomes: a comprehensive review, Journal of Negative Results in Biomedicine, Sep 9, 2019
- High Intensity Negative Ion Generator, Oregon State University Student Affairs Counseling & Psychological Services
- Ozone & Negative Ion Generators, American Academy of Allergy, Asthma & Immunology, May 9, 2015
- Comparative Examples of Noise Levels, iac Acoustics
- RabbitAir BioGS Filter Features
- Healthy Indoor Air, University of Illinois Extension
- Best Vacuums for Allergy Sufferers, Consumer Reports, June 18, 2019
- Short-term exposure to low levels of air pollution linked with premature death among U.S. seniors, Harvard T.H. Chan School of Public Health, Dec. 26, 2017
Undated citations were retrieved October 18, 2019