Indoor air quality

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GreenYour Indoor air quality

Buy an air filter

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Buying an air filter (also known as an air purifier or air cleaner) can improve indoor air quality (IAQ) by eliminating pollutants like VOCs, dust, tobacco smoke, and mold from your home or office.

How to buy an air filter

  1. Assess air cleaning requirements: First, find out what needs to be filtered out of your air—mold, formaldehyde, tobacco smoke, radon—so that you can determine the appropriate air cleaning solution.
  2. Choose an appropriate air filter type: There are many methods for cleaning air, some more effective than others. Check out the following resources to find out what’s available to you.
  3. Determine filter size: If you’ve uncovered some nastiness in your air and the only way to combat it is with a filter, measure your room to determine what size you’ll need.
    • Do you want to filter all of the air in your home or office? Then you may want to consider a filter that’s attached to your air conditioner or furnace. If you’ve got a small space or require air cleaning in only one room, then look into portable options.
    • Most air filters list a Clean Air Delivery Rate (CADR), which measures the square footage that can be cleaned effectively, and is often broken down by pollutant type. Generally speaking, you'll want a filter with a CADR rating that’s at least 2/3 the size of your room. So, if your room is 450 square feet, you’ll want a CADR that’s at least 300. Just remember, the CADR is calculated for rooms with ceilings up to 8 feet high—any higher and you’ll need to compensate with a higher CADR than average. If a filter doesn’t specify a CADR, you can determine it by dividing the flow rate by the filter efficiency. For example, a filter that operates at 300 cubic feet per minute with a 50 percent efficiency would have a CADR of 150.
  4. Look into certified air filters: Check out these certifiers to find an air filter that’s tested and sure to be efficient and effective for your needs.
    • ENERGY STAR certifies portable electric room air cleaners, but only if they’re 35 percent more energy-efficient than conventional models. Any air filter bearing the ENERGY STAR logo will save $16 or more every year.
    • GreenGuard is a watchdog group not affiliated with the air purifier industry. It publishes this online guide for products that have been tested and certified by the organization. Though not a vendor, GreenGuard can be a useful tool for finding an appropriate air cleaner.
    • The Association of Home Appliance Manufacturers (AHAM) certifies portable electric room air cleaners by running random sample tests for cleaning effectiveness for tobacco smoke, dust, and pollen. The group's product listings can be viewed by brand name, manufacturer, room size, and pollutant.

Find it! Air cleaning products

According to the EPA, the three basic strategies for maintaining indoor air quality are: 1) controlling pollution sources, 2) providing ventilation for your home or office, or 3) using a portable air cleaner.[1] Exploring the first two options before buying an air cleaner can help save money from a purchase, as well as energy costs. But if you're stuck indoors with known pollutants, sometimes an air filter is the only option.

Buying an air cleaner helps you go green because...

  • It can help to eliminate harmful pollutants, like VOCs and irritants such as dust, tobacco smoke, and mold from your home or office.

The quality of indoor air is an increasing concern as evidence suggests that air inside homes and buildings is often more polluted than outdoor air. And since people spend about 90 percent of their time inside, indoor air pollutants are now on the top five list for environmental health risks.[1][2] Pollutants are routinely brought into homes or offices and have negative health and environmental effects. Paints and carpeting, for instance, can contain volatile organic compounds (VOCs) that contribute to ground-level ozone.

For those with recurring respiratory, sinus, or asthma-related problems, or those concerned about the quality of their indoor air, single-room air cleaners are one way to address these concerns. Although many filters on the market today can’t effectively remove large airborne particles, like cat dander and dust mites, they can reduce the adverse health effects of a select group of pollutants (depending on the model).[2]


A new, specialized type of air cleaner—called ionic air cleaners—often produce ozone (O3), which is itself a pollutant and a health concern.[3] At upper atmospheric levels, ozone exists in high concentrations (called the ozone layer) which protect the earth from ultraviolet (UV) radiation. Although at ground-level, ozone is normally formed by the reaction of air (or hydrocarbons and nitrogen oxides in the air) with sunlight, ionic air cleaners produce ozone as a byproduct. This byproduct contributes to the growing problem of ground-level ozone, which is responsible for decreased agricultural yields since it interferes with the photosynthesis of many plants and is therefore considered a pollutant. It can also irritate respiratory function, causing increased rates of asthma, chest pain, shortness of breath, and inflamed lung tissues.[4]


  • ground-level ozone: The main component of smog, ground-level ozone is formed when volatile organic compounds (VOCs) react chemically with nitrogen oxides (NOx) when it is sunny and hot outside. Many urban areas have high levels of this summertime pollutant but rural areas can have increased ozone levels too as wind can carry ground-level ozone hundreds of miles from where it originates. Breathing ozone can cause a number of respiratory health problems plus it damages ecosystems and vegetation including crops.
  • ozone layer: A gaseous layer in the stratosphere where ozone (O3) gas is at the highest concentrations in our atmosphere. It forms a protective layer over the earth by filtering out shorter wavelength ultraviolet (UV) rays (photons or UV rays) that would otherwise be harmful to most lifeforms on earth's surface.
  • volatile organic compounds (VOCs): Organic solvents that easily evaporate into the air. VOCs are emitted by thousands of products, including paints, cleaning supplies, pesticides, building materials, and furnishings, and they may cause immediate and long-term health problems.

External links

Commercial building resources

Residential resources