Glossary of Air Purification Terms |

Glossary of Air Purification Terms

How to Choose a Purifier

Air purification comes with it's own set of terms. Chemicals, acronyms, and industry terms can be unfamiliar to first-time buyers. These terms are defined below to make picking the correct purifier a breeze!



Stands for the Association of Home Appliance Manufacturers, a trade association of the home appliance manufacturing industry, whose members include the manufacturers of portable room air cleaners. AHAM develops and maintains technical standards for various appliances to provide uniform, repeatable procedures for measuring specific product characteristics and performance features. The AHAM seal (usually found on product packaging) will list Clean Air Delivery Rate (CADR) numbers for tobacco smoke, pollen and dust.



Stands for Clean Air Delivery rating, a standard designated by the AHAM. The CADR indicates volume of filtered air delivered by an air cleaner. The higher the ratings, the faster the unit filters the air. Typically the AHAM rates the CADR of a unit for tobacco smoke, pollen, and dust.



Formaldehyde is a chemical widely used in industrial processes, including manufacture of building materials and household products.  It is one of the VOCs, or volatile organic compounds, that turn into gas, or vaporize, at normal room temperatures. Formaldehyde is an irritant and even at low levels can cause anything from allergic reactions, burning in the eyes, nose, and throat, rashes, coughing, and nausea. It comes from a wide variety of sources, including adhesives used in particleboard, fiberboard, and plywood; preservatives in paints and coatings; some insulation materials, burning wood, natural gas and kerosene; car engines; and cigarettes.

Learn more about Formaldehyde on the CDC's site



High Efficiency Particulate Air (HEPA) filters are a type of filter that has met specific US government standards. To qualify as HEPA, a filter must remove 99.7% of all particles 0.3 microns of greater from the air that passes through it.



Minimum Efficiency Reporting Value (MERV) is a way to categorize filters based on the air filter's effectiveness. The higher the MERV rating, the more air particles a filter captures. MERV ratings range from 1 to 16, with 1 being the least efficient and 16 being the most efficient. These ratings are based on the filter's ability to remove particles 3 to 10 microns in size.



Refers to a micrometer, one millionth of a meter or about 1/25,000th of an inch. Microns are used to measure the size of airborne particles, many of which are too small to be seen with the naked eye but still easily inhaled. These microscopic particles can be distributed throughout your home or office and have detrimental effects on your health. Most of the dangerous particles are 0.3 microns or smaller. For example, a dust mite is usually between 0.1 and 0.3 microns, while a strand of human hair is typically between 30 and 120 microns.



Ozone is a molecule made up of three oxygen atoms:  O3. Ozone is great for humans when it's way up in the atmosphere; it helps protect us from ultraviolet (UV) light from the sun.  But down by the ground, where we can breathe it in, it's a component of smog and dangerous to human health. Ozone is produced indoors by some photocopiers, laser printers, electrostatic or ionizing air cleaners, and ozone generators. Ozone reacts with molecules in our bodies' airway lining, inflaming the tissue and impairing the airways' ability to protect us from microbes, allergens, and toxic chemicals.  When that happens, our bodies respond by contracting muscles in the inflamed airways and coating them with fluid, making it harder to breathe. Ozone can also trigger asthma and allergies, and can worsen the symptoms of pneumonia, emphysema, bronchitis, and other respiratory ailments. While short-term effects of ozone exposure are reversible, long-term effects may not be--studies have shown that repeated exposure can permanently scar lung tissue, and may even reduce your immune system's capacity to fight respiratory bacterial infections.

For more information in Ozone, visit the EPA's site.



Stands for Volatile Organic Compounds. VOCs are organic chemicals, i.e. any compound of carbon, although there are some exceptions. VOCs have very low boiling points, meaning that they will change from a liquid or solid state and evaporate into the air at room temperature. There is a vast number and variety of VOCs, both man-made and naturally occuring. Most odors that you encounter throughout that day are, in fact, VOCs. While some VOCs play important roles in the environment, others can be dangerous to human health, especially indoors, where they are most concentrated. Most negative effects from VOCs are the results of long-term exposure. VOCs are practically ubiquitous, but some prominent sources are paints and protective coatings, the CFCs contained in cleaning products and refrigerants, tobacco smoke, car exhaust, adhesives and building materials. Chemicals such as benzene and formaldehyde are prominent VOCs. Reactions to VOCs include sinus irritation, headaches, nausea, and allergic reactions.