Allergies can affect almost any aspect of your life. Outdoor sources of allergens are plentiful, especially in the spring and summer, but even indoor air can be full of particles that can irritate your lungs. Air purifiers use a variety of technologies to clean the air in your home, reducing the airborne pollutants that might set off an allergic reaction.
Types
Air purifiers can be broken down into two major styles: active and passive. Passive purifiers draw air into the unit and clean it, usually either by a filtration system or by attracting particles to charged plates. Active purifiers either charge the air in the room or produce a substance that attacks particles outside of the unit, altering particles to reduce odor or causing them to fall out of the air. Some units use both types of technology at once for maximum cleaning effect.
Mechanical Filtration
The most basic type of air purifier uses a physical filter to clean the air. Air flows through the filter, which traps airborne contaminants. The most effective type of air filter is the high efficiency particulate arrestor filter, also known as HEPA. According to the Department of Energy, to bear the HEPA standard a filter must catch 99.97 percent of all particles 0.3 microns in size or larger. HEPA filters are excellent at capturing pollen, spores and large particles, and often include an activated carbon filter to remove smoke, pet dander and odors from the air.
Electronic Air Purification
Electronic air purification systems rely on the fact that opposite electrical charges attract. One type of electric purifier charges all particles that pass through it with a negative charge, causing them to be attracted to any positively charged surface. Some units feature positive collection plates in the unit, while others rely on the charged particles' tendency to stick to walls and other surfaces in your home. These units can treat a large volume of air quickly, but because they do not remove particles from circulation immediately, the effect can take longer to notice.
Ozone
Another type of air purification system uses ozone to destroy biological contaminants and odor. Ozone is an unstable molecule that can oxidize and damage particles it touches. Unfortunately, ozone is also harmful to humans in high concentrations, so many states have restricted the sale of ozone generators for home use. Most electronic air purifiers create some ozone as a byproduct, but the amount is usually low enough to be harmless.
Ratings
One way to compare the effectiveness of air purifiers is to look for ratings. The Association of Home Appliance Manufacturers rates air purifiers with a Clean Air Delivery Rating figure, which is based on how fast a given unit can purify the air. According to AHAM, dividing the square footage of a room by two-thirds will give you the minimum CADR rating needed to clean the air within the room.
References
- Allergy Consumer Review: Air Purifiers - Everything You Need To Know But Were Afraid To Ask
- Allergy and Asthma Foundation of America: Air Filters
- Department of Energy: Specification for HEPA Filters Used By DOE Contractors
- Air Purifiers: Technology of Air Purifiers
- Association of Home Appliance Manufacturers: What is AHAM's Clean Air Delivery Rate?
