Devices to Improve Air Quality:
Air Filters, Hepa Vacuum Cleaners,
and Air Conditioners
After you've followed many of the recommendations we've already listed, you may still feel that your house could be more pollutant-free. In fact, there are a few more things you can do to reduce biological and chemical particles, including use of efficient air filters, vacuums, and electric air purifiers.
Vacuuming Up Pollutants
One of the most effective ways to get rid of accumulated dust and other particles is to thoroughly vacuum it up. Carpets, drapes, and upholstery-places where dust mites thrive and other particles cling-benefit from frequent cleanings. A vacuum cleaner is an effective way to pull these particles out from deep within the fabric. So try to vacuum well twice a week.
But you have to be careful. Standard vacuum cleaners backdraft-that is, they push particles right back out through their exhaust. I Consumer Reports found that canister-style cleaners spew out more dust than uprights. Eureka, Hoover, Nilfisk, Euroclean, and Miele now manufacture vacuum cleaners outfitted with HEPA and ULPA filters, which are very effective for capturing even minute particles (see below). This option may add $100 or more to the cost of the vacuum cleaner. Patty Arlotta, the mother of a child with allergies and asthma, bought a Hoover "Wind Tunnel" for $200. "I waited until it was on sale, plus I had a coupon. It's normally $300," she says.
While you can't use a HEPA or ULPA filter on vacuum cleaners that are not made for them, there are vacuum cleaner bags for standard machines that trap and retain small particles better than standard bags.
Air filters work by capturing particles and gasses in some type of material before they can enter a room. Your home probably already has a few filters-in the furnace, air conditioners, ducts, and in your vacuum cleaner. Replace these frequently as they get dirty and clogged. You can also substitute more efficient filters for the old ones to improve filtration. And you can install them in places that usually don't have filters, like window screens and fans, and heating/cooling vents.
Filters can be used on ventilation systems to block pollutants in outdoor air before they enter the house. This only works in tightly constructed houses, though. Many homes, especially older ones, have air coming into the house from many places besides the ventilation system. An alternative is to filter indoor air through forced-air heating and cooling systems. Indoor air is pulled through the system and a filter, then forced back into living spaces. While outdoor air may enter the house, it will eventually get filtered as air moves through the forced-air system. Filtration is optimal if air-handling fans continuously operate.
Portable electric air purifiers, quite popular these days, have some advantages and some drawbacks. Prior to purchasing one of these devices, take as many steps as possible to reduce the entry of dust, pollen, mold, VOCs, and particulates into your house. Electric purifiers will not remove all pollutants and are much more effective contending with minor pollution. Preventing indoor air pollution in the first place will be more effective in the long run. If you've taken steps to keep your home pollutant-free, but feel that particles and gasses continue to find a way into your house, then a portable filter may help. It is important to select the right type of machine for your purposes (see below).
Filters for Household Appliances and Portable Air Purifiers
Various types of filters are on the market. Some only block gasses, while others only eliminate particles. You can buy combination filters, for some purposes, that will do both. Filters that effectively block tiny particles, such as HEPA and ULPA filters, restrict airflow. This may mean having more powerful fans, in some cases, to push air through them. The following are some of the most frequently used filters.
Activated charcoal filters, for forced-air furnaces, air conditioners, and portable air purifiers, absorb gasses, such as some VOCs. They won't remove formaldehyde and other low-weight gasses, but there are specially treated charcoal filters that will. Activated alumina filters will also absorb low-weight gasses, including formaldehyde.
Medium efficiency particulate filters, used in ducts, furnaces, and air conditioners, capture 25 to 45 percent of the particles in the filtered air. This means that they will block pollen and mold spores, but tiny particles may escape them. The thicker the filter, the greater the probability that it will capture tiny particles. But thick filters may block airflow, which could damage machines. So make sure your furnace and air conditioner can handle them.
Electrostatic filters, usually made of vinyl, polyester, or polystyrene, rely on static electricity to attract particles to them. They filter only larger pollens, mold spores, and particles. Electrostatic filters also need to be changed often, about every month or so. They are useful in appliances that cannot be fitted with higher-efficiency filters, such as standard vacuum cleaners and window air conditioners. 3M's Filtrete filters can be cut to fit. You can order them directly from 3M or Priorities.
High Efficiency Particulate Arresting (HEPA) filters are the most efficient filters available, for use in everything from specially equipped vacuum cleaners and filtration machines to central heating ducts. Made of fiberglass or polyester, a HEPA filter's tiny pores catch nearly everything-about 95 percent of what's in the air, including particles as small as 0.3 microns (a micron is one-millionth of a meter). Because of its ability to capture so much, a HEPA filter requires a powerful fan to push air through it. This means that some devices, such as vacuum cleaners, must be equipped to use them (see section on vacuum cleaners). Installed improperly, a HEPA filter used in appliances not designed for them may cause some damage. HEPA filters are also more expensive than other filters but last for a few years.
ULPA filters, used in Nilfisk vacuum cleaners, are similar to HEPA filters; they catch even smaller particles-as small as 0.12 micron.
You don't necessarily need a HEPA filter for every air conditioner, duct, and furnace in your home, especially if you've attempted to improve indoor air quality by eliminating sources of pollution. Instead, you may want to use a combination of filters. For example, medium efficiency particulate and activated charcoal/alumina filters could be installed in ducts, furnaces, and forced-air heating and cooling systems to catch gasses, pollen, mold spores, dust, and other larger particles. HEPA filters used in vacuum cleaners and portable air purifiers would clean up any remaining small particles.
Selecting and Using a Portable Electric Air Purifier
While portable air cleaners are not absolutely necessary, they can improve indoor air quality if they are used in conjunction with other measures. The best performing machines are the room-size type. Desktop or tabletop models don't work as well, according to Consumer Reports. Larger air purifiers pull more air through them at a faster rate than do smaller ones, thus cleaning more efficiently. Desktop or personal air purifiers are really too small to be of value.
Not all machines are equipped to eliminate gasses and particles. Look for a purifier that has a combination of filters that will handle both. Don't assume it will remove formaldehyde and other VOCs. Ask the salesperson.
We don't recommend ozone machines and negative-ion generators (which also produce ozone). At high concentrations, ozone attacks gas molecules, but does nothing to eliminate dust and other particles. Negative-ion generators spew out electrons that attach themselves to particles in the air and give them a negative charge. The negatively charged particles then cling to walls and furnishings. Salespeople will sometimes claim that you can simply clean the walls to remove pollutants, but this method of air purification is hardly efficient. And if the particles lose their negative charge before you've wiped them up, they'll just re-enter the air. The greater problem, though, is that ozone is a lung irritant. Asthmatics and children may feel discomfort and may possibly experience some respiratory problems while these machines are in operation.
Portable air purifiers work best when they are operated continuously. While using them, close the door to prevent contamination from other rooms. Also, if you have central heating or cooling, seal off the heating and cooling vents where the machine is operating to prevent entry of polluted air and escape of clean air. This may require installing a window air conditioner in the room for cooling in summer and a heater that is independent of the central system. If you want to purify several rooms, it may be more practical to install a central air filtration system. For more information about air purifiers, read the EPA booklet "Residential Air-Cleaning Devices: A Summary of Available Information" available by calling the Indoor Air Quality Hotline.
During the summer months, unbearable heat waves and high humidity prompt many of us to turn on air conditioners. Air conditioners have the added benefit of reducing relative humidity levels, which helps keep mold and dust mites in check. And since windows are kept closed, use of an air conditioner means less pollen entering your home. Use of fans, while more energy-efficient, can be problematic for asthma and allergy sufferers because they make pollutants airborne and pull unfiltered outdoor air inside (though you can buy fans with filters from Priorities and Harmony).
Central air conditioners can be fitted with HEPA filtration systems designed by Allermed Corporation and Pure Air Systems. Window air conditioners generally cannot be fitted with HEPA filters, but you can use electrostatic filters, such as 3M's Filtrete, for improved filtration.
To find the most energy-efficient air conditioners, consult Consumer Reports' annual buying guide and Consumer Guide to Home Energy Savings by Alex Wilson. Note that, in general, the higher the energy-efficiency or SEER (Seasonal Energy Efficiency Rating) of the air conditioner, the less effective it is at reducing relative humidity. To compensate, Rick Heede, a researcher at the Rocky Mountain Institute and author of Homemade Money: How to Save Energy and Dollars in Your Home, suggests lowering the air conditioner's fan speed on humid days to keep coils cool and, if your air conditioner has a recirculation setting, use it. Both of these books also offer tips on how to decrease your energy usage.
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