Air Filters for Allergy Sufferers
Close-up of household air filter
There are many products on the market that claim to reduce or cure allergies due to indoor-air-quality problems. We see commercials on TV and ads in magazine touting household appliances that use electricity to clean the air in small areas of rooms. However, these devices are very expensive and they do in fact only clean the air in a limited (less-than-room-size) space.
So is there an effective way to keep indoor air as allergen-free as possible? Yes, in fact, there are several, ranging from pretty darn expensive to very reasonable. Let's take a look at them:
Whole-house electronic air cleaners do the same job at a relative fraction of the cost of some of the room-size units, and they’ve been on the market for years (but not as well-advertised).
The nice thing about whole-house electronic air cleaners is that no particle is too small to be captured by them, so they can collect bacteria and mold spores? And even smoke! However, they require a standard household air filter to be mounted ahead of them to catch larger particles, and it's best to keep the furnace fan running all the time so the filter is constantly cleaning the air.
The downside of electronic air cleaners is that they may snap with an electrical discharge when they are dirty, they create small amounts of ozone (the "clean smell" that advertisers like to brag about), and they don't remove vapors or odors from the air. Also, they see a rapid falloff in efficiency as they get dirty, so regular cleaning is important. And they should be installed when the home is being built, since they are difficult and expensive to install after the furnace or air-handler is in place.
Some gimmick air cleaners claim to be electronic, but most work poorly if at all. A true electronic air cleaner requires electric power and is usually at least 4 inches thick. (We often hear people touting "electrostatic" air cleaners as a less-expensive alternative to the electronic types. They fit into standard air-filter holders, and they require no electric power. The idea is that they develop a static charge from the air, which may work somewhat during the winter when there’s a lot of static charge in the air, but what about in summer, when mold and pollen are most active?)
An "almost HEPA" air filter is a good alternative to an electronic air cleaner. These 4-inch-thick pleated filters do almost as good a job as electronic air cleaners. They filter more over a longer period of time, since their efficiency remains high even after they get dirty. They don't snap, crackle or pop, they don’t create ozone and they don’t require a pre-filter.
But on the down side, they have to be replaced every three months, and they are much more expensive than standard filters. Due to their size, these filter systems also are best installed along with the furnace.
An activated-charcoal filter is the only solution if the allergy sufferer is bothered by odors or chemicals. Activated charcoal and certain other man-made substances can absorb both, but there has to be sufficient depth to the product to do much absorbing. I've seen gimmicky air filters with charcoal grains placed here and there, but I doubt that they do any good. Something that will remove odors and chemicals must be filled at least an inch thick, and, since these devices aren’t made to remove dust, dander and spores, they require pre-filters.
Some more good news about activated-charcoal filters, though: They are very durable, because the charcoal can be reactivated several times by baking it. That means that they don't have to be replaced nearly as often. The upshot is that if your client has allergies, you can offer help. Work with a knowledgeable HVAC professional to provide the most effective and cost-effective solution.