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ACAAI > Patients & Public > Resources > Ask the Allergist

Home Environment Control Measures

Q:  A few months back I heard an allergist on television talking about the Ionic air filters being toxic to the lungs. I have had these air filters for a few years in every room, and have Copd caused by allergies. I was wondering where there was a resource of which I could find out more information as to what problems these air filters cause,as I certainly don't need anymore problems with my lungs. I have searched the internet but the only thing it brings up is sales of these air filters, even though I put in toxic lungs etc when searching.

A:  These are not really air filters. They are usually advertised as ‘clean air machines’ or ‘air purifiers.’ The ionization changes the charge on the particle and it sticks to the next thing it comes into contact with. There is usually not enough air flow to effectively filter many particles, so they provide minimal benefit as air cleaners. The health risk comes from the ozone they produce which is toxic to the nose and lungs. Here is a link to the EPA (Environmental Protection Agency) web site on this:

The better thing to use is either a HEPA room air cleaner rated with a Clean Air Delivery Rate (CADR) for the size room you are using it is. For central air cleaning a furnace filter with a MERV rating of 11 or 12 will help filter the particles blown through heating and air conditioning system.

Q:  Are air purifiers to the benefit of the asthmatic patients?

A:  I am assuming that he’s asking this question in the context of using an "air purifier" in the home.

  • There are no magic "air purifiers".
  • It is better to think of how can we move air through a filtration device to reduce the amount of allergens or irritating particles in the air which may be breathed in and trigger symptoms in the asthmatic.
  • Filtration can be either free standing (room air cleaners) or part of the forced-air heating and air-conditioning (HVAC) systems.
  • The best room air cleaners have HEPA filters and are rated by independent test to have a CADR (Clean Air Delivery Rating) to clean certain size rooms. There are several good brands available. (Hunter, Honeywell, and Austin Air to name a few) They are most effective in removing fine particulates and allergens like cat allergen. These are good for use in the bedroom.
  • Any type of machine that generates Ozone should not be used. The ozone may be irritating to the airways even at low levels. There is no such thing as "good" ozone.
  • High efficiency furnace filters can also help reduce particle and allergens in the air. They are rated by ASHRAE by Minimum Efficiency Rating Values (MERV). The most efficient filters available for home use have MERV 12 ratings. Brands include AllergyZone or 3M Filtrete
  • Using a combination of a HEPA room air cleaner in the bedroom and a efficiency furnace filter is the best approach.

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