Air filters range from small, inexpensive desktop models to whole-house air conditioning systems. Some do you a lot better than others. Some, in fact, are worthless. The ones that work are a real blessing, though.
‘I almost always prescribe air filtration,’ says Dr. Boxer. ‘I feel it’s helpful. I’ve seen asthma patients who were helped immensely by just using an air filter.’
‘Air filtration is certainly a very natural way of controlling symptoms,’ says Dr Falliers. There are dozens of products, and each has to be examined for what it does and doesn’t do.’
Air filters may be installed in the ductwork of either your warm-air furnace or air conditioning system. Or you can buy portable models that sit anywhere in the room. Or even hook up to the cigarette lighter in your car. Portable units can sometimes be rented.
Activated Charcoal Filters
The odor-eating capacity of activated charcoal varies with the humidity and temperature of the air in the room, the concentration of fumes, and the type of odors in the air. Dr. Guy O. Pfeiffer, of Mattoon, Illinois, studied activated charcoal filters and found that they’re generally pretty good for absorbing cooking and food odor’s (even from burned dinners and foods such as garlic, onions, cheese, and citrus); cigarette and tobacco odor’s; diesel and petrol fumes; smog and ozone; and the odor’s from pets, mothballs and perfume.
Charcoal is slightly less powerful against pollen, coal smoke, mildew, chlorine, fish odor, and some noxious gases. And it’s useless against carbon monoxide and formaldehyde. Installed piggyback with another type of filter, however, charcoal can be helpful; one catches what the other misses.
Electronic Air Cleaners
The most common type of electronic air cleaner is the electrostatic precipitator. Until a few years ago, electronic air cleaners were standard equipment for treating asthma and respiratory allergy. They act much like an electromagnet for air pollution: a fan draws in particles, zaps them with an electric charge, and collects them on a plate.
The charged particles are supposedly taken out of circulation. However, J. Gordon King, a consultant in air contamination, writes that although electrostatic precipitators are popularly advertised as being 95 to 99 percent efficient, they’re not.
In reality, says Mr. King, electrostatic air cleaners available for home use rarely trap more than 80 percent of the particles in the air. What’s worse, efficiency can drop to as low as 20 percent within a short period of time – especially for bigger particles like pollen (Respiratory Care).
That means electrostatic air cleaners are no more effective than putting a sheet of gauze over your mouth. And the charged particles that escape the filter build up on walls and furniture faster than if no cleaner was used at all. To top it all off, all electronic air cleaners produce ozone, a highly toxic gas which causes headaches in some people. So you may not want to bother with them at all.
HEPA (High Efficiency Particulate Air) Filters. These filters work a lot better than electronic air cleaners. Air that’s been cleared by a HEPA is free of 99.97 per cent of all contaminating particles, according to the US National Bureau of Standards. That’s about as clean as you can get in today’s environment. And they maintain their efficiency throughout their operating life of two to five years. HEPA filters work well against pollens, molds, yeast, and other fungi, bacteria and viruses – a boon to allergy sufferers prone to frequent colds and flu attacks. HEPA filters have been known to relieve hay fever and asthma symptoms within ten minutes to half an hour. When potassium permanganate or activated charcoal is added, a HEPA filter can clear the air of jumbo particles like dust and pollen as well as minute chemical odors.
HEPA units with metal casings are better for chemically sensitive people than units with casings made of pressboard (which contains formaldehyde) or plastic.
HEPA filters did wonders for reducing nightly asthma attacks for asthmatic children at a summer camp in West Virginia, according to the camp’s medical director Dr. Merle S. Scherr. In his report, Dr. Scherr emphasized that HEPA units are an important part of the treatment of allergic asthma (West Virginia Medical Journal).
HEPA units are also a godsend for preventing nightly asthma attacks for asthmatic children at home in winter. Normally, cold nights require furnaces to work harder, so furnace fans circulate more dust – and trigger more asthma.
But when HEPA filters were tested on eighteen children with hard-to-control asthma, the children collectively logged 140 nights of undisturbed sleep with the use of the filter, as compared with only forty-five peaceful nights without the filter.
This … not only relieved the parents of having to get up in the night and care for these children,’ say the researchers who conducted the study, ‘but we feel that the child, if well-rested, felt better, performed better during the day and was probably more resistant to illness.’ Several of the children were also able to cut down on their asthma medicine, and they no longer missed any school (Annals of Allergy).