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Helpful Terms to Know

The following are definitions commonly associated with indoor air quality.


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  • Airborne particles include smoke, smog, bacteria, household dust, pet dander, mould 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 through ordinary furnace filters and return to the air in your home. This can negatively impact your indoor air quality.

  • An allergen is a substance capable of producing a reaction in people sensitive to allergens. In the case of people with asthma, allergens that are inhaled can trigger symptoms such as coughing, wheezing and shortness of breath. Allergens that may cause asthma symptoms include animal dander, dust mites, mould and pollen.
  • Allergies are an abnormally high sensitivity to certain substances, such as pollen, certain foods or microorganisms. Common indications of an allergy may include sneezing, itching and skin rashes.
  • Asthma is a chronic, inflammatory lung disease characterized by recurrent breathing problems. Symptoms can be triggered by allergens, as well as infection, exercise, cold air and other factors.
  • Bacteria are living organisms, microscopic in size, which usually consist of a single cell. Most bacteria feed on organic matter and produce waste products. Bacteria are everywhere—on everything we see and touch, and even in the air we breathe.


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  • Chemical emissions are gases or particulates that have been released into the air.

  • Carbon monoxide is a highly toxic gas that is colourless, odourless 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 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 is composed of a wide variety of particles including dead skin from humans and pets, finely ground plant and insect parts, minute particles of sand and soil, and fabric fibres. Daily activities can stir up dust into the air. Dust can trigger allergic reactions in sensitive people, and can cause sneezing, runny nose and itchy/watering eyes.
  • Dust mites are tiny microscopic creatures related to ticks and spiders. Dust mites feed on skin flakes and can be found throughout the home, in mattresses, pillows, carpets and furniture. They produce airborne particles that can trigger allergic reactions or asthma episodes when inhaled by people who are sensitive to them.
  • Dust mite debris is made up of the excrement and fragments of dust mites.


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  • The electrostatic charge of Filtrete™ Air Filters acts like a magnet to attract and capture particles that can pass through fibreglass filters or other non-charged pleated filters. A Filtrete™ Filter with electrostatically charged fibres 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.

  • A forced air system is a heating and cooling system in which air is blown by a fan through air channels or ducts to rooms.
  • Formaldehyde is a volatile organic compound (VOC). Potential sources in the home include pressed wood products such as particleboard or fibreboard, smoking, and glues and adhesives.


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  • HEPA stands for High Efficiency Particulate Air. This is a rating system 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.

  • 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.


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

  • The 3M MPR (Microparticle Performance Rating) reports a filter's ability to capture tiny particles between 0.3 and 1 micron in size.
  • Microparticles are tiny airborne particles measuring between 0.3 and 1.0 micron. These include fine dust, smoke, smog, bacteria and some pet dander and pollen particles.
  • Mould spores are generated from mould, which is a fungus that grows in humid conditions. These spores can produce allergic reactions.
  • Non-electrostatic filters include 3-month pleated, washable and fibreglass filters that do not have electrostatically charged fibres. Filtrete™ Brand 1" and 4" residential filters with electrostatically charged fibres have been proven to perform better than 1" and 4" residential non-electrostatic filters.


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  • Parasitic cysts are egg-like sacs formed by the larva of a parasite. Sometimes found in unfiltered tap water, parasitic cysts can cause serious gastrointestinal infection and illness if consumed.

  • Pet dander is made up of shed animal skin cells and dried saliva. It is extremely lightweight and tiny (approximately 2.5 microns in size) and can stay airborne for hours before settling on surfaces. Pet dander can be problematic for people sensitive to pet dander. If they are allergic to dander, it can worsen breathing problems.
  • Pollen is made up of light, dry protein particles from trees, grasses, flowers and weeds. It is carried by the wind and can a potent stimulator of allergic reactions.
  • Radon is a colourless, odourless 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.


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  • Smoke can be generated by 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. While it can cause the typical allergic reaction like sneezing and runny nose, exposure to smoke can also cause burning eyes, bronchitis and even trigger asthma attacks to people who are sensitive.

  • A virus requires host cells to survive. Once inside our cells, viruses can cause diseases. Like bacteria, viruses can be found nearly everywhere—particularly in modern, tightly sealed homes. Airborne particles in your indoor air can carry viruses from place to place, and from person to person.
  • A VOC is a compound that vapourizes at room temperature. Common sources that may emit VOCs into indoor air include cleaning and maintenance products, and building and furniture materials. In sufficient quantities, VOCs can cause eye, nose and throat irritations, headaches, dizziness, visual disorders and memory impairment.

    Some VOCs are known to cause cancer in animals, and 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 VOCs typically found in public and commercial buildings.