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Asthma Health Center

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Asthma and Air Filters


Types of Air Filters continued...

Germicidal air cleaners use ultraviolet (UV) lights to kill bacteria, viruses, and molds that pass through the area with the UV light. Such UV lights can be included with other air cleaner devices, which use a fan. We are unaware of any research demonstrating that the addition of germicidal UV lights improves respiratory symptoms in people with lung disease. However, they have been used for decades to reduce the risk of infection with tuberculosis among staff and visitors in hospitals who are actively treating such patients.

Ozone generators are devices that intentionally produce high concentrations of ozone to clean the air in a room. They are often used to decontaminate rooms after smoke exposure following a fire. Ozone causes bronchospasm in people with asthma, even in low concentrations, and thus should be avoided.

Whole-house air cleaners may be used if your home is heated or air-conditioned through ducts. With a whole-house air cleaner, HVAC system includes air filters designed to reduce the accumulation of dust and dirt in the ducts and coils of the system. These simple filters cost less than a dollar each to replace every month or two, but they only remove large particles, not the small particles in the house that are inhaled into the lungs. You can buy more efficient replacement filters (usually for 6 to 20 dollars each) which will remove many smaller particles. These are often pleated or coated with an electrostatic charge. However, these replacement filters clog quickly in dusty environments, reducing airflow through the system, causing a reduction in the heating or cooling efficiency.

Permanent whole-house air cleaners can be added to an HVAC system, but the cost is several hundred to a few thousand dollars for the unit and the installation. Disadvantages include the ozone byproduct of electrostatic air cleaners; the need for frequent cleaning of the plates; the need to keep the fan running continuously (24/7) to clean the air, and the electricity cost and noise associated with the large blower fan running continuously.

Choosing an Air Filter

Ask the following questions before purchasing an air filter:

  • Is it large enough? Will the unit clean the air in a room the size of my bedroom every four to six minutes at a fan speed I can tolerate? An adequate size is determined by the device's clean air delivery rate (CADR). The Association of Home Appliance Manufacturers (AHAM) rates air cleaners according to their clean air delivery rates; see the AHAM web site for details.
  • How difficult is it to change (or clean) the filter? Ask for a demonstration. How often does the filter (or the two different filters) have to be changed (in an average home with a smoker, which is the worst case)? How much do the replacement filters cost? (Also check the cost when buying them online)
  • What is the estimated cost to run the unit continuously for a year?
  • How much noise does the unit make? This is very important for the HEPA units that include a fan. The CADR rating is only when you run the fan on the high speed, which is always the noisiest. Is it quiet enough to run while you sleep? (Turn it on and try it, even though you will probably be in a store and may not get a true sense of just how noisy it is in the quiet bedroom environment.)

If you or a loved one has asthma symptoms and there's a smoker in your home, an air filter is likely to improve your asthma control. If there is no secondhand smoke in your home, air cleaners may not help your asthma. If you are the one smoking, a room air cleaner will only help the nonsmokers in your home, not you. The bottom line on using air filters to prevent an asthma attack? If you’re a healthy individual living in a relatively unpolluted environment, there's probably no need to spend the money.

Reviewed on May 18, 2014
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