A Breath of Fresh Air
These days, there is a lot of discussion about indoor air quality (IAQ) and how we can improve the quality of the air we breathe in our homes. Installing an air cleaner or filter is a way to improve your home’s IAQ.
The type of air cleaning device you choose to install can depend on a number of factors: the type of heat and air delivery system in your house, the type of pollutants or irritants you’re looking to remove and the amount of investment you’d like to make. Air cleaners can be in the ductwork of forced-air systems (also known as in-duct air cleaners); if you have a hot-water baseboard system or radiators, you’ll need to use a portable air cleaner. There are various types of filters available including mechanical filters, electronic air cleaners, ultraviolet (UV) and hybrid filters.
The efficiency of an air cleaner is measured in terms of the particle size that the device can capture. Most conventional mechanical filters have minimum capture efficiency for particles approximately 0.3 microns in diameter. A micron is one micrometer, which is one millionth of a meter or approximately 1/25000 of an inch. You can select a particle removal air filter by looking at its efficiency in removing airborne particles from the air stream that passes through it. This efficiency is measured by the minimum efficiency reporting value (MERV) for air filters installed in the ductwork of HVAC systems. MERV ratings (ranging from a low of 1 to a high of 20) also allow comparison of air filters made by different companies. The clean air delivery rate (CADR) is often used to compare portable air cleaners. The CADR is the product of the net air volume generated by an air cleaner and the minimum filtration efficiency for removing particles of smoke, dust, and pollen from a room.
Mechanical filters draw air through a flat, pleated or high efficiency particulate air (HEPA) surface to trap particles. HEPA filters are the most efficient mechanical filters for removing small particles. These highest efficiency air cleaners remove 0.3 micron (1 micron = 1 millionth of a meter) sized particles at a minimum of 99.97% efficiency. Maintenance of these filters is very important. Dirty filters are not effective removing pollutants from the air and also block air flow. Checking the recommendations for frequency of replacement and coordination with your home environment will provide the best results. For example, if remodeling your home or if there is a smoker, you will need to check or replace your filter more frequently. Different types of filters have different life expectancies, pleated filters can last up to 90 days, while washable filters should be washed every 90 days and replaced every 5 years.
Electronic air cleaners trap and filter up to 98% of pollutants from the air passing through your heating and cooling system. They work by placing an electric charge on airborne particles and then collecting these charged pollutants like a magnet. This air cleaner can capture microscopic impurities like dust, smoke and smog particles in addition to larger particles like mold spores and cat dander. Collected pollutants are removed by cleaning the plates in the sink or dishwasher.
Ultraviolet (UV) air treatment lamps are installed in forced-air heating and cooling systems. The UV air treatment systems ‘zap’ mold spores and certain live, airborne bacteria passing by the lamp to prevent them from being recirculated into your home's air. The shortwave lights are similar to those used in hospitals, laboratories and commercial kitchens. UV air treatment can kill up to 87% of certain airborne bacteria in the air passing through your heating/cooling system.
Some air cleaners (called ozone generators) use an electrical charge to generate ozone and can create more problems than they alleviate. Although ozone is a necessary part of the upper atmosphere (10-30 miles above us), in the part of the atmosphere we breathe, ozone is a potent lung irritant. It can have damaging health effects, especially for persons with asthma and other lung diseases, children and the elderly. It is produced directly by ozone generators and indirectly by ion generators and some other electronic air cleaners. The FDA has set a limit of 0.05 parts per million of ozone in indoor air.
Consumer Reports, the National Institute of Occupational Safety and Health (NIOSH), and the U.S. EPA concluded that tabletop and room unit ozone generators are not effective in improving indoor air quality. Studies have found that while some indoor air pollutant concentrations decline in the presence of ozone, other pollutants increase. In fact, upon reaction with ozone, some previously undetected, toxic chemicals emerge in indoor air, including formaldehyde and other aldehydes. The EPA has published a document called "Ozone Generators Sold as Air Cleaners," which is available for free on the EPA website.
Replacing your hot air furnace’s air filter with an air filter with a higher MERV can improve your house’s air quality for a relatively small cost. Installing a UV treatment lamp will remove mold spores and certain types of bacteria, will probably require a professional to install and have a higher cost. Which type of filter you decide to install will depend on what type of air distribution system in your house and your budget.
For more information on air cleaners, refer to the following organizations: Association of Home Appliance Manufacturers (AHAM), Clean Air Device Manufacturers Association, Consumer’s Union and the FDA Medical Device Listing.
