An air cleaner is a great addition to any home to rid the air of these contaminants. There are a numerous variations of air cleaners, and becoming familiar with them is a good way to determine your family's specific needs to breathe easier and avoid choosing a product that may do more harm than good.
HEPA Filtration Systems use filters specifically designed to remove different types and sizes of contaminants. HEPA stands for High Efficiency Particulate Arrestance, which means it is 99.97% efficient at trapping particles 0.3 microns or larger. These types of air cleaners are bypass systems when used centrally on your furnace, because this filter media would be too restrictive on air flow if used in the furnace filter slot. The pre-filter removes large particles (skin, hair), the HEPA filter removes very small particles (viruses, pollen, mould) and the VOC filter removes gases and odours (cooking odours, smoke, off-gassing from new materials). These bypass systems require little maintenance (replacement of filters every 3 - 6 months) and are often used in hospitals to clean the air of viruses (SARS, flu, etc.).
Ultraviolet Light Air Cleaners
use UV-C light to kill microorganisms traveling through the ventilation system and filters to trap the dead spores (as even dead mould, etc. is also an allergen). The UV-C light penetrates the cell wall and causes a molecular rearrangement of the microorganism's DNA, which prevents it from reproducing. A microorganism that cannot reproduce is inactivated and considered dead. Some UV lights are sold just to kill what passes by the light, so an efficient filtration system is still required for the particulate matter.
Electronic air cleaners use an electrical field to give particles a positive or negative charge and trap charged particles on oppositely charged plates. They lose efficiency quickly when the plates are not cleaned regularly. At best they are 50% efficient when dirty and need to be cleaned every 3 - 7 days to maintain manufacturer's efficiency claims. They must be completely dry before put back into the system, which may take up to 24 hours. When these units are dirty, and there is no other furnace filter in the system, your furnace has no protection against debris passing through the ventilation system.
Electrostatic Furnace Filters draw in the dirty air, which passes through a filter and captures particles by electrostatic attraction. No electricity is required. However, they ARE NOT AIR CLEANERS. They are very efficient furnace filters, trapping up to 94% of particles 1 micron and larger, but do very little for the 0.3 mircon sized particles, which are the ones more likely to invade your lungs. An electrostatic furnace filter is a great addition to the system when a HEPA air cleaner is present.
Ion Generators use electricity to ionize particles and are subsequently collected on metal plates, although these negatively charged airbourne particles tend to 'stick to' anything around them (drapes, tables, floors) and cause black looking residue near the machine. Some allergists say that they have long recommended HEPA cleaners over ionizers because of fears about ozone output. Ozone emissions rise with the increased particles collected on the plates. Air ionizers make up about 25 percent of the air cleaner market as they have a large budget for infomercials and other advertising, however Consumer Reports tested a number of these popular 'air-cleaning' machines and found that most did more harm than good, producing potentially harmful ozone while doing a poor job of removing dust, smoke and pollen. People with asthma or respiratory allergies are especially sensitive to indoor ozone, an irritant that can worsen asthma, deaden sense of smell, raise sensitivity to pollen and mold, and may cause permanent lung damage. The May 2005 issue of Consumer Reports was published only two months after Sharper Image (one ionizer manufacturer) agreed to pay Consumers Union, (publisher of Consumer Reports), $525,000 in legal costs after a federal judge dismissed a libel lawsuit alleging the publisher printed false information in an October 2003 article about it's Ionic Breeze's ability to reduce airborne particles.
Whenever you are shopping for an air cleaner, consider your specific lifestyle needs, the efficiency, level of maintenance required, cost and reputation of the manufacturer before you buy. Have all air cleaner systems maintained by a professional regularly at intervals suggested by the manufacturer and clean or replace filters when required for best results and proper function.