Air purifiers help to improve overall air quality by filtering out contaminants, and they can be used in homes, offices and vehicles or even be worn around the neck. Studies have shown that indoor air is often more polluted and toxic than outdoor air, because of a buildup of smoke, mold, pet dander, chemicals from furniture and more that gets trapped in buildings with poor ventilation. Indoor air pollution can cause a host of health problems, from headaches and asthma to cancer and heart disease. An indoor air purifier can drastically reduce your risk of illness and improve your sense of well-being.
How They Work
Air purifiers use a number of different methods to filter indoor air. For most models, an internal fan draws air into the unit through a series of filters that remove contaminants before releasing the air back into the room. Some fan-less air purifiers consist of filter cartridges that mount to heating and air conditioning ducts. Ionizers offer another purification method. Available with or without a fan, they work by emitting microscopic negative ions that act as magnets for airborne particles. Once joined, their combined weight forces them to the ground where they are no longer a threat to be inhaled.
Airborne contaminants that contribute to indoor air pollution include dust, pet dander, mold spores, pollen, smoke and pathogens such as bacteria and viruses. In addition to bacterial pollutants are chemical pollutants that originate from furniture, varnish, building supplies, carpeting, plastics, cleaning supplies, paint and more. Even if you don't suffer from allergies or asthma, you could still be feeling the effects of indoor air pollution, which can at times feel more like a mild cold.
Types of Air Purifiers
The most commonly used types of air purifiers include absorptive carbon filters, pleated or woven screens made of polypropylene or glass microfibers, electrostatic filters and ultraviolet germicidal irradiant (UVGI) lamps. Other types include photocatalytic oxidizers, ionizers and ozone generators. It is routine for air purifier manufacturers to combine two or more types into a single product, thereby eliminating the widest variety of airborne contaminants.
Granular activated carbon is an incredibly porous material used to absorb odors and volatile organic compounds (VOCs). A single gram of activated carbon has a 500-square-meter surface area, so a small amount goes a long way. Carbon is primarily found in air purifier pre- or post-filters to deodorize a space. Most often, activated carbon filters are used in conjunction with other types of purifiers.
True HEPA and HEPA-Type Filters
HEPA (high efficiency particulate air) filters are renowned for their ability to capture very small airborne particles. HEPA filters come in two basic varieties: true HEPA and HEPA-type filters. True HEPA filters are tested and certified for effectiveness. With a true HEPA filter, 99.97 percent of all airborne particles 0.3 microns or larger cannot pass through. HEPA-type filters use similar technology, although they are not effective at stopping tiny particles. Purifiers with HEPA-type inserts stop around 90 to 95 percent of 2- to 3-micron particles. IQAir makes very comprehensive purifiers that use their patented HyperHEPA filter, which traps particles as small as 0.003 microns, far smaller than most filters can stop.
UV Germicidal Lamps
Select whole-house air purifiers as well as numerous room models feature a germicidal ultraviolet lamp. UV light is especially effective at destroying living microorganisms that can cause disease. Breaking the microscopic lifeforms down and disrupting their DNA prevents them from replicating, and they die. UV lamps produce a trace amount of ozone, which can be harmful to humans in higher amounts. UV lamps require a fan to force air past the light. Whole-house, duct-mounted filters don't need a fan because the furnace or air conditioner moves the air through the purifier, past the UV lamp.
Electrostatic Filters and Ionizers
Utilizing the same basic principles that govern static electricity, an electrostatic filter creates an electrically charged field through which particle-filled air passes. As it moves through, airborne contaminants are charged or ionized. They next encounter a metal collection plate or set of blades charged oppositely that attracts the charged particles like a powerful magnet. Electrostatic filters have the advantage of being reusable once their collection plate is cleaned.
Ionizers work in a similar fashion. They use an electrically charged needlepoint or some other surface, creating negative ions or anions and sending them out into a space. Once they come into contact with airborne contaminants, they are electrostatically attracted to them. Their combined mass is too heavy to float, so gravity takes hold and drags them to the floor, out of breathing range.
The designs of the purifiers themselves are as numerous as the purification methods are. The basic designs are room, whole-house and personal purifiers. Room models consist of desktop and floor or tower units that typically cover spaces ranging from 80 to 800 square feet. Whole-house systems may be comprised of several room units, such as those offered by Alen, or duct-mounted units offered by Honeywell and other makers. Drop-in HVAC filters made by 3M and other brands serve as air purifiers as well. Personal air purifiers include small desktop units as well as neck-worn ionizers that give new meaning to "personal bubble." These units constantly emit negative ions to guard against airborne contaminants on buses and planes and in other enclosed spaces where sickness lingers.
Prices and Brands
The cost of an air purifier varies widely, depending upon the brand, type, capacity and overall quality. Air purifiers are available for as little as $20 or as much as $1,200. Whole-house systems can cost up to $3,000 with installation. Brands include familiar names like Honeywell, Holmes, Hunter, Bionaire, Whynter and Whirlpool. Less well-known makers of high-quality units include IQAir, Alen and Austin Air. Besides the initial purchase, ongoing costs include replacement filters and lamp bulbs. Filters may last anywhere from 3 months to 5 years, while some are designed for a lifetime of use with the proper maintenance.
Operational features common to many air purifiers include conveniences such as filter change indicator lights, electronic or digital one-touch controls, programmable timers and multi-speed fans. Air purifiers are typically very energy efficient, costing just pennies a day to operate.