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May 13, 2017

Best HVAC Filters for Patients with Bad Allergies

For patients with bad allergies, management of symptoms include not just medications and allergy shots, but also avoidance. Avoidance entails not just physically avoiding allergy particulates, but also removing them from the air you breath as much as you can.

Outside of a school or work environment, the home is where a patient may spend a great deal of time. The home is where one can easily take steps to improve the air quality and therefore reduce allergy symptoms and need for (more) allergy medications.

Step 1:

Install good filters at ALL air intake ventilator grills. These air intake grills are typically found in a wall or ceiling and is where air goes IN. A good air filter would remove all particulates in the air over time that may cause allergy symptoms (ie, pollen, mold, dust, etc). Installing a good filter in this location (rather than at the air handler itself) also prevent the ducts and HVAC system itself from becoming dirty with dust and allergens over time.

Air filters are rated in how efficiently they perform this task using the MERV scale. MERV stands for Minimum Efficiency Reporting Value. MERV scales range from 1 to 16 with "1" being the least efficient and "16" describing the highest efficiency.

Obviously, avoid MERV 1 - 4 which does a poor job of removing allergen particulates.

MERV 5 - 13 is reasonably efficient in removing airborne allergen particulates.

As such, for patients with bad allergies, one should purchase air filters classified between MERV 13 - 16. These filters are expected to remove all allergen particulates at about 75% efficiency after a single pass. Before a patient gets all worried about 75% not being as good as 99%, keep in mind that in a home, air would pass through this filter multiple times. Such air recirculation would result in 75% of the particulates being removed from the air with each pass. After several hours, this would result in 99% particulate removal from the air. For those curious, HEPA filters have MERV ratings 17 - 20 which exceed 99% efficiency on a single pass, but honestly is probably not necessary for entire home use and can even potentially damage the air handler due to excessive strain (a lot more power is required to push air through). HEPA filters make more sense used in a portable unit for a single room (ie, bedroom).

3M uses a different rating system for some of their filters called MPR (Microparticle Performance Rating). MPR and MERV are basically the same thing. MPR 300 is equivalent to MERV 6; MPR 1000 = MERV 11; MPR 1500 - 2200 = MERV 12.

These filters can all be found and purchased on Amazon.

The key concept for clean air in the home using high MERV (or MPR) filters is "air recirculation". If you have a home's door or window constantly open, you are constantly bringing in NEW air along with allergens floating within. This goes to step 2.


Step 2:

Especially during bad allergy seasons, keep all windows and doors to the outside closed as much as possible to prevent allergens from the outside from getting in. Doing otherwise is defeating the purpose of the HVAC air filter which cleans the air by air re-circulation.

With air re-circulation, one can achieve good air quality even with MERV 5 - 13.

This also means to keep the HVAC fan turned ON at ALL times (do not set to auto).

Step 3 (optional):

Add a portable HEPA filter unit to a single room, typically the bedroom, to further ensure clean air beyond that provided by the home's HVAC system with high MERV filters.

Good portable HEPA units include those made by Dyson and Alen.

Step 4:

Change all air filters quarterly ideally and semi-annually at the very least. The filters WILL become dirty over time and not perform as well.

Step 5 (optional):

For those paranoid about air quality, one can install multiple filters to the home's HVAC system. This basically means to install an air filter at the air intake grill, at the air handler unit, and where air comes out into a room. With such cascaded systems, you may need to hire a company to help in the install. However, a "simple" multi-filter system which I use in my home is to use a MERV 8 at the air intake grill and another MERV 8 in the air handler unit.

In a work situation, one can (try) and install a high MERV filter where air comes out into the room where you work. You may not have any power to change filters at the intake or air handler locations, but you might where air comes out. Obviously, you can keep windows/doors closed and purchase a portable HEPA unit for your own personal use.

Step 6:

If you go outside, you may want to consider wearing a personal respirator or face mask. Click here for more info.

Good luck!

Fauquier blog
Fauquier ENT

Dr. Christopher Chang is a private practice otolaryngology, head & neck surgeon specializing in the treatment of problems related to the ear, nose, and throat. Located in Warrenton, VA about 45 minutes west of Washington DC, he also provides inhalant allergy testing/treatment, hearing tests, and dispenses hearing aids. Google+ Christopher Chang, MD Bio

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