ASHRAE - The American Society of Heating Refrigeration and Air Conditioning Engineers.

Blower - In HVAC the fan in an air conditioner that distributes the filtered air from the return duct over the coil/heat exchanger. This circulated air is cooled/heated and then sent through the supply duct, past dampers, and through supply diffusers to the living/working space.

Carbon filters are most effective at removing volatile organic compounds (VOCs) from the air.

CFM Cubic feet per minute - HVAC term for the amount of air, in cubic feet, that flows through a given space in one minute. 1 CFM equals approximately 2 litres per second (l/s).

Electronic Air Cleaner - An electronic device that filters out large particles and contaminants in indoor air. It then electronically pulls out tiny particles that have been magnetized, such as viruses and bacteria, drawing them to a collector plate.

Electrostatic Air Filters
The electrostatic charge acts like a magnet to attract and capture particles that can pass through fiberglass filters or other non-charged pleated filters. A 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 or Furnace HVAC term for a type of heating system which uses air blown by a fan through air channels or ducts to rooms to transfer heat to the living or work space.

HEPA
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.

Humidifier - A humidifier is a household appliance that increases humidity (moisture) in a single room or in the entire home.

HVAC - HVAC is an acronym for heating, ventilation, and air-conditioning system.

Media Filters - Media based purification traps airborne particles by size exclusion. Air is forced through a filter and particles are physically captured by the filter. Higher-efficiency MERV filters use dense media with deep pleats to increase air/media surface contact. The media filters offer greater and longer holding capacity.

MERV Rating - The MERV (Minimum Efficiency Reporting Value) rating of a filter describes the size of the holes in the filter that allow air to pass through. The higher the MERV rating, the smaller the holes in the filter,the higher the efficiency.

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.

Pre-filters - Remove coarser impurities to reduce the frequency of cell cleaning or media filter replacing.

Relative Humidity - A measure of the percent of moisture actually in the air compared with what would be in it if it were fully saturated at that temperature. When the air is fully saturated, its relative humidity is 100 percent. The relative humidity should be kept between 40% and 60% in the average home.

Return Air - Air that is returned to a heating or cooling appliance from a heated or cooled space.

Static Pressure - In flowing air, the total pressure minus velocity pressure. The portion of the pressure that pushes equally in all directions.

Supply Duct - HVAC term for the duct(s) of a forced air heating/cooling system through which heated or cooled air is supplied to rooms by the action of the fan of the central heating or cooling unit.

Volatile Organic Compound (VOC)
A VOC is a compound that vaporizes 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.