Replacing filters to lower allergens

The simplest way of dealing with allergies is to get rid of whatever environmental thing it is that's causing the allergy. One way of doing that in the case of airborne allergens is to install a filter that will take the allergens out of the room air.

Although a filter is easy to install and can help the problem, it won't be as effective as, say, finding a new home for the cat or ripping up the carpeting if one of those is the cause of the problem.

But, as they say, filters can't hurt and better air quality will benefit everyone. The first step in thinking about this issue is to identify what it is that triggers the allergy of concern and find out what filters may be obtained for that. There are different filters that are best at stopping dog hair or dust mites or paint odors, for example.

Besides just trapping the allergens in the air, a proper filter can help you in other ways. All filters are prime targets for microorganism growths, and a filter that's designed for allergen trapping is apt to have a better treatment to cut down on the critters growing within. You should consider cleaning or changing the filter more often if that's your prime concern.

Dust mites and many other allergy provoking things grow much more in a warm humid environment, so just running the air conditioner will reduce them. However, a good filter will allow the air conditioner to work more efficiently, cooling the air better and using less power.

Another benefit to a good filter is that the rest of the air conditioner, and the ductwork in a central system, will accumulate less dirt and microorganisms over time if a proper filter is installed.

Please realize that we're talking in general terms throughout this article. There are many different levels of sensitivities and it's not possible to say accurately what kind of a filter will produce the optimum result. In many cases, such as the level of microbials that may grow in a filter, the safe level just isn't known, and the kind of growths will be radically different in different rooms. There are some people who say filters make things worse by trapping particles and then passing all the air in the room through them.

It may be best to consider this matter as something that needs to be addressed empirically - that is, try one type of filter and see how you feel, then try another and see what changes. If you have a hot air heating system, you can most likely put the same type of filter on it. It's vitally important that you change or clean any filter when recommended, every thirty days in most cases, or more often if it makes a difference.

Of the filters available, most are mechanical, that is, they trap pet dander and hair, dust mites, smoke and pollen. The other major type of filter is a gas phase filter, designed to trap odors such as building materials or paint, cooking odors and so on.

Air filter makers are faced with having to make a compromise. If a filter traps very very efficiently, it won't pass much air through. Modern technology has helped design filters that are much more effective than the floppy piece of foam usually supplied with an air conditioner, which basically protects the air conditioner more than it purifies the room air.

Filters are rated in terms of their arrestance, resistance, and MERV. Arrestance refers to the filter's ability to entrap particles, and you'll see figures generally between 85 and 95 percent in the specifications. Resistance refers to how much of an impediment the filter presents to the air flow. The lower the figure is the more air will go through the system and the less hard it will have to work. Figures from 07 to .20 inches initially are typical. A manufacturer will say the filter should be cleaned or replaced when it reaches .4 or .9 due to the accumulation of material. These numbers are specified in terms of "inches w.g." where w.g. stands for "water gauge" which can be used to measure pressure in the U.S. inch pound system…the rest of the world measures in Pascals.

MERV stands for Minimum Efficiency Reporting Value and is a figure of merit created by an industry group, the American Society of Heating, Refrigerating, and Air Conditioning Engineers (ASHRAE). Common MERV levels range between 4 and 12. A MERV 11 rating requires a 65% to 80% efficiency on 1 - 3 micron particles and greater than 85% efficiency on 3 -10 micron particles, for instance.

Bear in mind that all these numbers won't be what you actually get, since the tests are on just the media, not in an actual air conditioner, with standardized dust and other samples. Your particles are different, and the tests don't take into account things like the air that blows by the edge of the filter.

There are also HEPA filters you may see advertised. HEPA stands for High Efficiency Particulate Air filter and was developed during World War II to filter radioactive particles from escaping into the air from laboratories. HEPA filters are good but present too high a resistance to be used unless the air conditioner was specifically designed for it. You can't directly compare the filtering efficiency of HEPA and other filters as they're tested to different standards.

Most air filters to be used for trapping allergens are designed with several layers of paper, polyurethane, polypropylene, polyester and similar materials. Manufacturers claim advantages for the materials they use…some have a polyester layer that is tacky to retain more particles, others decry the use of polyester, saying it can't be cleaned well. You'll have to read about it and decide for yourself.

Some filters have a layer of activated charcoal, a substance long used to clean up odors. It works but its effectiveness is very different depending on the odor, and may get used up very quickly.

There's a new type electrostatic filter that doesn't need to be connected to a source of electric power, and is available as a general replacement. It takes advantage of the ability of polypropylene to be permanently charged with a baked-in charge. The filters use layers of poly charged with alternate polarities. This means that dust particles with a positive or negative charge are attracted as opposites attract to the oppositely charged layer.

So you'll want the best filtering you can get that will work with your air conditioner…but what's "best" is going to be different for each person since you want the filter that removes as much as possible of whatever's triggering your allergy. It's also necessary to get a filter that doesn't put too much resistance in the air flow. That doesn't necessarily mean you have to go with the same type of filter the air conditioner came with or even one the air conditioner maker suggests - but it does mean you can't make the air conditioner work harder than it was designed to.

There's lots of information from air filter makers if you do a simple search on the net or in the phone book under "Filters-Air" or similar headings.

If you're buying a filter for allergy relief you might also check with your health insurance company - it will cover all or part of the cost under some plans if you have a doctor write a prescription for a filter. That may be a relief all by itself!