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The following are definitions commonly associated with indoor air quality.

(airborne) particles
allergen (or allergens)
allergies
asthma
bacteria
chemical emission
CO carbon monoxide
combustion pollutants
(household) dust
dust (particles)
dust mite debris
dust mites
electrostatic
electrostatically charged
forced air system
formaldehyde
HEPA
humidity
irritant
lint
low toxicity
micron
Microparticle Performance Rating (MPR)
microparticles
moisture
mold
mold spores
non-electrostatic
pet dander
pollen
radon
smog
smoke
virus (viruses)
VOC volatile organic compound


(airborne) particles
Airborne particles include smoke, smog, bacteria, household dust, pet dander, mold spores, dust mite debris and pollen. These particles range in size between 0.3 to 100 microns. Considering that the average diameter of a human hair is 50 microns, these particles are so small that most pass right through ordinary furnace filters right back into the air in your home.

allergen (or allergens)
An allergen is a substance that's capable of producing an allergic reaction in people who are sensitive to allergens. In some people with asthma, allergens that are breathed in can trigger symptoms such as coughing, wheezing, and shortness of breath. Allergens that may cause asthma symptoms include animal dander, dust mites, mold, and pollen.

allergies
Allergies are an abnormally high sensitivity to certain substances, such as pollens, foods, or microorganisms. Common indications of allergy may include sneezing, itching, and skin rashes. Doctors typically diagnose allergies.

asthma
Asthma is a chronic, inflammatory lung disease characterized by recurrent breathing problems which can be triggered by allergens. (Infection, exercise, cold air, and other factors can also be triggers.)

bacteria
Bacteria are living organisms, microscopic in size, which usually consist of a single cell. Most bacteria use organic matter for their food and produce waste products as a result of their life process. Bacteria are everywhere. They are on everything we see and touch, and even in the air we breathe.

chemical emission
Chemical Emissions are the release or discharge of a chemical substance into the environment. The term generally refers to the release of gases or particulates into the air.

CO carbon monoxide
Carbon Monoxide is a highly toxic gas that is colorless, odorless and tasteless. It is created by the incomplete burning of natural gas or any other material containing carbon, including gasoline, kerosene oil, propane, coal and wood.

combustion pollutants
Combustion Pollutants are byproducts of the combustion or burning process. Burning fuels such as coal, oil, gas, and wood produces many pollutants, such as sulfur dioxide, nitrogen oxides, and particulates. Combustion also produces airborne emissions and solid waste such as ash and sludge.

(household) dust
Household dust is made up of a wide variety of things including dead skin from humans and pets, finely ground plant and insect parts, minute particles of sand and soil, fabric fibers from clothes, carpets, and upholstery. Dust typically accumulates in carpets, on horizontal surfaces, computer and TV screens, and sometimes clumps into dirty balls of fabric fibers, also known as "dust bunnies". Daily activities can stir up dust into the air. Like other allergens, dust can trigger allergic reactions to people who are sensitive and can lead to sneezing, runny nose, and itchy-watering eyes.

dust (particles)
Dust particles are made up of a wide variety of things including dead skin from humans and pets, finely ground plant and insect parts, minute particles of sand and soil, and fabric fibers from clothes, carpets, and upholstery. Dust typically accumulates in carpets, on horizontal surfaces, computer and TV screens, and sometimes clumps into dirty balls of fabric fibers, also known as "dust bunnies". Daily activities can stir up dust into the air. Like other allergens, dust can trigger allergic reactions to people who are sensitive and can lead to sneezing, runny nose, and itchy-watering eyes.

dust mite debris
Dust mite debris is made up of the excrement and fragments of dust mites, which are tiny microscopic animals related to ticks and spiders that live in virtually every home.

dust mites
Dust mites are tiny microscopic animals related to ticks and spiders that live in virtually every home. Dust mites feed on skin flakes and can be found throughout the home, including mattresses, pillows, carpets, and furniture. These creatures produce airborne particles that can trigger allergic reactions or asthma episodes when inhaled by people who are sensitive to them.

electrostatic
An electrostatic charge has been placed on the fibers of Filtrete filters so that they act like tiny magnets to attract and capture particles. A Filtrete filter with electrostatically charged fibers performs better than non-electrostatic filters. The actual effectiveness of an air filter in allergen reduction depends on a variety of factors including the amount of air that the filter processes, the nature of the allergens, and the rate at which the allergens are being introduced into the home. Electrostatic filters are most effective when new and clean.

electrostatically charged
Electrostatically charged fibers act like tiny magnets to attract and capture particles that can pass right through fiberglass filters or other non-charged pleated filters. A Filtrete filter with electrostatically charged fibers performs better than non-electrostatic filters. The actual effectiveness of an air filter in allergen reduction depends on a variety of factors including the amount of air that the filter processes, the nature of the allergens, and the rate at which the allergens are being introduced into the home. Electrostatic filters are most effective when new and clean.

forced air system
Forced Air System is a heating system in which heated air is blown by a fan through air channels or ducts to rooms.

formaldehyde
Formaldehyde is a volatile organic compound (VOC). Potential sources in the home include pressed wood products such as particleboard or fiberboard; smoking; and glues and adhesives.

HEPA
HEPA is an abbreviation for high efficiency particulate air [filter], a rating used by the Department of Energy to denote an air cleaner or filter that is 99.97% efficient or better at removing 0.3 micron-sized particles from the air passing through it.

humidity
Humidity is the amount of water vapor in the air.

irritant
An Irritant is a substance that, when breathed in, irritates the airways and can trigger asthma symptoms. Common examples include strong perfumes, cigarette smoke, and fumes from harsh cleaning fluids.

lint
Lint consists of particles and short fibers that fall off a fabric product during the stresses of use.

low toxicity
Substances of low toxicity are materials which have a low ability to produce irritation, illness or damage to an exposed organism.

micron
One micron is one millionth of a meter or approximately 1/25,000 of an inch. For comparison, a human hair is 50-70 microns thick.

Microparticle Performance Rating (MPR)
The 3M MPR (Microparticle Performance Rating) focuses on a filter's ability to capture smaller particles between 0.3 and 1 micron in size. Based on independent laboratory tests, 3M’s MPR measures a filter’s ability to capture submicron particles that make up 99% of the particles in the air, such as bacteria, smoke and smog. The MPR can be used to compare filters, however MPR cannot predict how a filter will actually perform in your home. The independent laboratory tests overstate the effectiveness of electrostatic filters, but still indicate that Filtrete filters with electrostatically charged fibers outperform all other non-electrostatic filters in their respective categories.

microparticles
Microparticles are the smaller particles in the air that are between 0.3 and 1.0 micron and include fine dust, smoke, smog, bacteria and some pet dander and pollen particles.

moisture
Moisture is diffuse wetness that can be felt as vapor in the atmosphere or seen as condensed liquid on the surfaces of objects; dampness.

mold
Mold is a fungus that grows in damp or very humid areas and generates spores that can produce allergic reactions.

mold spores
Mold spores are generated from mold, which is a fungus that grows in damp or very humid areas and can often produce allergic reactions.

non-electrostatic
Non-electrostatic filters include 3-month pleated, washable and fiberglass filters that do not have electrostatically charged fibers. A Filtrete 1" or 4" residential filter with electrostatically charged fibers will perform better than 1" and 4" residential non-electrostatic filters.

pet dander
Pet dander is made up of old scales; shed animal skin and dried saliva. It is extremely lightweight and tiny in size (approximately 2.5 microns) and can stay airborne for hours and settle on surfaces. Pet dander can be trouble for people who are sensitive to pet dander and if they are allergic to dander, it can worsen breathing problems.

pollen
Pollen is made up of light, dry protein particles from trees, grasses, flowers and weeds. It is carried by the wind and is a potent stimulator of allergic responses.

radon
Radon is a colorless, odorless gas that seeps up from the earth. It is created by the natural decay of uranium in the earth, and exists naturally in many locations. Radon may present a serious health risk when it accumulates in basements or crawl spaces beneath homes.

smog
Smog is the most visible form of air pollution. It is a brownish-yellow, hazy cloud caused when heat and sunlight react with various pollutants emitted from industry, cars, pesticides and oil-based home products. The word "smog" is a combination of the words smoke and fog.

smoke
Smoke can be generated by several things including cigarettes, cigars, wood burning stoves, and fireplaces. In addition to several known carcinogens, smoke can contain fine particles composed of wood tars, gases, soot, and ashes. In addition to causing the typical allergic reaction like sneezing and runny nose, exposure to smoke can cause burning eyes, bronchitis, and can even trigger asthma attacks to people who are sensitive.

virus (viruses)
A virus is incredibly small and simple. It's not really a living organism, in that it doesn't have a cellular structure, and it can't metabolize food or reproduce itself outside of a host cell. Once inside our cells, viruses can cause diseases. Like bacteria, viruses can be found nearly everywhere - particularly in our modern, tightly sealed homes. Unfortunately, the tiny particles floating around our houses carry viruses from place to place, and from person to person.

VOC volatile organic compound
Volatile Organic Compounds (VOC): Compounds that vaporize (become a gas) at room temperature. Common sources that may emit VOC's into indoor air include housekeeping and maintenance products, and building and furniture materials. In sufficient quantities, VOC's can cause eye, nose, and throat irritations, headaches, dizziness, visual disorders, memory impairment; some are known to cause cancer in animals; some are suspected of causing, or are known to cause, cancer in humans. At present, not much is known about what health effects occur at the levels of VOC's typically found in public and commercial buildings.

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Tips for improving air quality in and around your home at The Lung Association - Your Healthy Home.