Below is the Guardian Technologies™ glossary defining the words and acronyms used when referring to air purifiers. Also, don’t miss out on the definitions related to our home environment products.

Activated Carbon — Specially treated carbon that has been exposed to heat around 800–900 degrees Celsius. The great thing about activated carbon is that it has a large internal surface area and can trap a lot of impurities inside it.

Airborne — Used to describe any particles or substances that float in the air. Airborne particles are the reason that air filters are used to clean air in a given area.

Air Changes per Hour — Used to describe the amount of times per hour that an air purifier can clean and re-circulate all of the air in a room.

Allergen — A normal substance that causes an acute defensive reaction in a person's immune system. Common allergens are pet dander, smoke, and pollen, although the list of possible allergens is long and varied. When a person has a reaction to an allergen that person is said to be allergic to it.

Animal Dander — Tiny scales of animal skin.

Bacteria — Microscopic, single-celled organisms that have a cell wall and a specific shape depending on the type of bacteria. Bacteria have no easily identifiable nucleus. There are many types of bacteria, and although many are harmful to humans there are some that actually help.

Biohazard — Used to describe any time of biological waste. Often, this biological waste is pathogenic in nature or contaminated in some way.

Black Wall — An occurrence common with ionic air purifiers that happens when the air around an ionic type air purifier becomes negatively charged. This negatively charged area causes airborne particles to stick to surrounding surfaces (often the wall behind the device) and cause a buildup of dirt and bacteria. Black Wall can be a breeding ground for microscopic organisms.

Coronal Discharge — A type of air purifier that uses ozone to clean the air, a Coronal Discharge device is sometimes referred to as a "thunderstorm in a box". The air inside a coronal discharge device is charged with between 5,000 and 10,000 volts of electricity. The massive shock causes unstable bonds to form between single atoms of oxygen (O) and Oxygen molecules (O2). Ozone then attacks any airborne particles in the surrounding area (O3).

CADR — Clean Air Delivery Rate is a measure of the air purifier's ability to reduce smoke, dust, and pollen particles in the 0.1 to 11 micron size range from the air. CADR is defined as " the rate of contaminant reduction in the test chamber (1008 sq. ft) when the unit is turned on, minus the rate of natural decay when the unit is not running, multiplied by volume of the test chamber as measured in cubic feet.

CFM — Cubic feet per minute.

Electrostatic Precipitators — These blow air into a cell where it is given a positive electrical charge. The air is then blown through special stainless steel plates which carry a negative charge and attract dust and allergen. This type of air purifier emits ozone as by-product.

EPA — Acronym for the U.S. Environmental Protection Agency, the Federal agency responsible for the regulation of pesticides, toxic chemicals, hazardous wastes, and toxic pollutants in water and air.

Filter — Any porous device that allows the passage of air but traps airborne particles, thus cleaning the air.

HEPA Filter — HEPA stands for High Efficiency Particulate Air. HEPA filters were developed during World War Two as a safety device for the Manhattan Project, the American effort to develop nuclear weapons. HEPA filters use glass fiber as a filter and can clean particles out of the air. Though brittle, these filters are now widely used in a variety of filtration devices, and are widely considered to be the best air filter available to the public.

Histamine — A substance your body injects into your bloodstream to help you stay alert. However, it is often triggered by allergens. It causes fluid to be released into the skin (which causes swelling and hives), and when released into the sinuses can cause a runny nose and watery eyes.

Indoor Air Pollution — The term used to describe the amount of contaminants in the air inside a building. Indoor air pollution can often be worse than outside air pollution due to poor ventilation. Unfortunately, it is often ignored. About 80 per cent of all indoor air pollution is human skin. The remaining 20 percent is usually made up of dust mites, pet dander, smoke, pollen, sweat, and chemical compounds from various substances.

Indoor Air Quality (IAQ) — A term used to describe how polluted the air inside a confined space is. The IAQ of any building is measured according to guidelines set by the government and is used as a measuring stick for the efficiency of air purification and filtration systems.

Ionizers — These use high voltage electricity to create negative electrons. These electrons run up the length of a pointed spike, or needle, where they stream into the air and attract oxygen molecules. At this point, they become negative ions and are attracted to airborne particles. These molecules build up around the particles until they become too heavy to remain air borne and float to the ground. This process is known as agglomeration.

Negative Ion — Odorless, tasteless, and invisible molecules that we inhale in abundance in certain environments. Think mountains, waterfalls, and beaches. Once they reach our bloodstream, negative ions are believed to produce biochemical reactions that increase levels of the mood chemical serotonin, helping to alleviate depression, relieve stress, and boost our daytime energy.

Natural Ventilation — Occurs when outdoor air enters through open windows and doors and through cracks and leaks in the home.

Negative Pressure — Condition that exists when less air is supplied to a space than is exhausted from the space, so the air pressure within that space is less than that in surrounding areas.

Ozone — A special type of oxygen molecule caused by bonding a third oxygen atom to an oxygen pair. This is most often accomplished using ultraviolet light. Ozone (O3) is highly unstable and reacts with air borne particles by launching the extra oxygen at anything near it. The oxygen atom reacts with the air borne particle, causing a tiny explosion and the destruction of the particle. Ozone purifiers are highly effective against both dust and microscopic organisms, but can be unhealthy if a person is exposed to large quantities.

Off-Gassing — The production of gases from the chemical deterioration of a substance over time.

Purifier — A purifier is a device that cleans the air of viruses and microscopic organisms as well as dust and allergens. Purifiers are especially useful for people who suffer from allergies and wish to live an allergy-free lifestyle.

Volatile Organic Compounds (VOCs) — Compounds that evaporate from housekeeping, maintenance, and building products made with organic chemicals. These compounds are released from product that are being used and are in storage. In sufficient quantities, VOCs 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 VOCs typically found in public and commercial buildings.