ACID AEROSOL: Acidic liquid or solid particles that are small enough to become airborne. High concentrations of acid aerosols can be irritating to the lungs and have been associated with some respiratory diseases, such as asthma.

ACTIVATED CARBON: Activated carbon is a highly adsorbent powdered carbon that purifies by adsorption. It is made by burning carbon-based materials at very high temperatures to create a porous internal structure that provides a huge surface area that is ideal for removing odorous compounds and gases. Only one pound of activated carbon typically has a surface area of 125 acres. Activated carbon is so effective that it's used in military gas masks.

ADVERSE HEALTH EFFECT: Any abnormal, harmful, or undesirable effect (occurrence) on the physical, biochemical, biological, or behavioral well-being of a person that results from being exposed to pollutants in the environment.

AHAM: Association of Home Appliances Manufacturers

AIHA: American Industrial Hygiene Association

AIR: A mixture of gasses constituting a compressed fluid tied to the planet by gravitational attraction. Air is 79.0% nitrogen, 20.9% oxygen, and less than 0.1% a mixture of carbon dioxide, argon, helium, and hundreds of other gasses originating from natural and man-made sources.

AIR CHANGES PER HOUR (ACH): Air Changes Per Hour measures the amount of times an air purifier cleans and re-circulates all of the air in a given room during one hour. The more changes per hour the more effective the filter is.

AIR CLEANING: An IAQ control strategy to remove various airborne particulates and/or gases from the air. The three types of air cleaning most commonly used are particulate filtration, electrostatic precipitation, and gas sorption.

AIR CONDITIONING: The process of treating air to meet the requirements of a conditioned space by controlling its temperature, humidity, cleanliness, and distribution.

AIR EXCHANGE RATE: The rate at which outside air replaces indoor air in a space. Expressed in one of two ways: the number of changes of outside air per unit of time air changes per hour (ACH); or the rate at which a volume of outside air enters per unit of time as cubic feet per minute (CFM).

AIR POLLUTANT: Any substance in air that could, in high enough concentration, harm man, other animals, vegetation, or material. Pollutants may include almost any natural or artificial composition of airborne matter capable of being airborne. They may be in the form of solid particles, liquid droplets, gases, or in combination thereof. Generally, they fall into two main groups: (1) those emitted directly from identifiable sources and (2) those produced in the air by interaction between two or more primary pollutants, or by reaction with normal atmospheric constituents, with or without photoactivation. Exclusive of pollen, fog, and dust, which are of natural origin, about 100 contaminants have been identified and fall into the following categories: solids, sulfur compounds, volatile organic chemicals, nitrogen compounds, oxygen compounds, halogen compounds, radioactive compounds, and odors.

AIR PURIFIER: An air purifier is a device that removes contaminants such as viruses, microscopic organisms, pet dander, dust and allergens from the air. Purifiers are especially beneficial to people who suffer from allergies and asthmatics. They also help to reduce and eliminate odors from pets, tobacco smoke and gasses.

AIR QUALITY INDEX (AQI): The AQI is an index for reporting daily air quality. There are six categories each assigned a specific color to make it easier for people to understand the air pollution and associated health concerns for their community.

AIRBORNE PARTICULATES: Total suspended particulate matter found in the atmosphere as solid particles or liquid droplets. Chemical composition of particulates varies widely, depending on location and time of year. Airborne particulates include: windblown dust, emissions from industrial processes, smoke from the burning of wood and coal, and motor vehicle or non-road engine exhausts.

ALLERGEN: A chemical or biological substance (e.g., pollen, mold, animal dander, or house dust mite proteins) that induces an allergic state or reaction, characterized by hypersensitivity.

ALLERGIC RHINITIS: Inflammation of the mucous membranes in the nose that is caused by an allergic reaction.

ANTIMICROBIAL: Agent that kills microbial growth (i.e., chemical or substance that kills mold or other organisms). See "Biocide" and "Fungicide."

ASBESTOS: A naturally-occurring mineral fiber that can cause cancer.

ASTHMA: A condition marked by recurrent attacks of difficult or labored breathing and wheezing resulting from spasmodic contraction and hypersecretion of the bronchi. It is caused by exposure to allergens such as drugs, foods, environmental pollutants, or intrinsic factors.

BIOLOGICAL CONTAMINANTS: Agents derived from, or that are, living organisms (e.g., viruses, bacteria, fungi, and mammal and bird antigens) that can be inhaled and can cause many types of health effects including allergic reactions, respiratory disorders, hypersensitivity diseases, and infectious diseases. Also referred to as "microbiologicals" or "microbials."

BIOCIDE: A substance or chemical that kills organisms such as mold.

BUILDING ENVELOPE: Elements of the building, including all external building materials, windows, and walls, that enclose the internal space.

BUILDING-RELATED ILLNESS (BRI): Diagnosable illness whose symptoms can be identified and whose cause can be directly attributed to airborne building pollutants (e.g., Legionnaire's disease, hypersensitivity pneumonitis). Also: A discrete, identifiable disease or illness that can be traced to a specific pollutant or source within a building. (Contrast with "Sick building syndrome").

CARBON DIOXIDE: A colorless, odorless, nonpoisonous gas which results from fuel combustion and human activity indoors. Elevated levels of carbon dioxide indicate ineffective ventilation indoors.

CARBON MONOXIDE: A colorless, odorless, poisonous gas which results from incomplete combustion.

CARCINOGEN: A substance that can cause or contribute to cancer.

CEILING PLENUM: Space between a suspended ceiling and the floor above that may have mechanical and electrical equipment in it and that is used as part of the air distribution system. The space is usually designed to be under negative pressure.

CHEMICAL SENSITIZATION: Evidence suggests that some people may develop health problems characterized by effects such as dizziness, eye and throat irritation, chest tightness, and nasal congestion that appear whenever they are exposed to certain chemicals. People may react to even trace amounts of chemicals to which they have become "sensitized."

CLEAN AIR DELIVERY RATE (CADR): The CADR indicates the total volume of air that a specific air purifier cleans of a particular pollutant in one minute. CADR delivers test results for three main pollutants: tobacco smoke, pollen and dust. The higher the numbers, the faster the unit filters the air.

CUBIC FEET PER MINUTE (CFM): A measure of the volume of a substance flowing through air within a fixed period of time. Indoors, it is the amount of air measured in cubic feet that is delivered and exchanged in one minute.

DECIBEL (DB): A unit of sound measurement. Sound doubles in loudness for every 10 decibels.

DISINFECTION: A chemical or physical process that kills pathogenic organisms.

DUST: An air suspension of particles (aerosol) of any solid material, usually with particle size less than 100 micrometers.

DUST MITE: A microscopic arachnid, commonly Dermatophagoides pteronyssinus or Dermatophagoides farina.

EMISSION: Pollution discharge from a source.

ENERGY STAR: Energy Star is a program that was developed in 1992 by the EPA to identify and promote products that are energy efficient. Devices carrying the Energy Star rating are generally 20-30% more efficient than non-rated models, which save the consumer money and help protect the environment.

ENVIRONMENT: The sum of all external conditions affecting the life of an organism.

ENVIRONMENTAL FACTORS: Conditions other than indoor air contaminants that cause stress, comfort, and/or health problems (e.g., humidity extremes, drafts, lack of air circulation, noise, and over-crowding).

ENVIRONMENTAL TOBACCO SMOKE (ETS): Mixture of smoke from the burning end of a cigarette, pipe, or cigar and smoke exhaled by the smoker (also secondhand smoke (SHS) or passive smoking).

EPA: EPA is the acronym for the US Environmental Protection Agency. The EPA is responsible for implementing laws that promote public health by protecting our air, water and soil from harmful pollution.

EXPOSURE: An event in which an organism comes in contact with a chemical or biological agent.

FABRIC FILTER: A cloth that catches dust particles.

FORMALDEHYDE: A colorless, pungent, and irritating gas, CH20, used chiefly as a disinfectant and preservative and in synthesizing other compounds like resins.

FUNGI: A separate kingdom comprising living things that are neither animals nor plants. The kingdom Fungi includes molds, yeasts, mushrooms, and puffballs. In this course, the terms fungi and mold are used interchangeably.

FUNGICIDE: A substance or chemical that kills fungi.

HEPA: High Efficiency Particulate Air (filter).

HYPERSENSITIVITY DISEASES: Diseases characterized by allergic responses to pollutants. The hypersensitivity diseases most clearly associated with indoor air quality are asthma, rhinitis, and hypersensitivity pneumonitis. Hypersensitivity pneumonitis is a rare but serious disease that involves progressive lung damage as long as there is exposure to the causative agent.

HYPERSENSITIVITY PNEUMONITIS: A group of respiratory diseases that cause inflammation of the lung (specifically granulomatous cells). Most forms of hypersensitivity pneumonitis are caused by the inhalation of organic dusts, including molds.

IDEAL COVERAGE AREA: The recommended coverage area is for optimal purification in an area with 8 ft. ceilings at 6 air changes per hour, meaning that all the air in the space is circulated through the purifier 6 times per hour. The maximum coverage area can be up to three times larger at about 2 air changes per hour.

INDOOR POLLUTION: Indoor air pollution describes the contaminants inside of a building. It is often ignored, but can actually be worse than outdoor air pollution due to poor ventilation. Sources of indoor pollution include tobacco smoke, pet dander, dust mites, mold, pollen, pesticides and gases such as radon and carbon monoxide. Breathing air inside a habitable structure, often highly polluted because of lack of exchange with fresh oxygen from outdoors. Solvents, smoke, paints, furniture glues, carpet padding, and other synthetic chemicals trapped inside contribute to an often unhealthy environment.

INDOOR AIR QUALITY (IAQ): Indoor Air Quality (IAQ) is a term referring to the air quality within a confined space, especially as it relates to the health and comfort of the occupants. It can be affected by such things as mold, bacteria and gases and is becoming an increasingly more concerning health hazard than outdoor air. The IAQ is measured according to guidelines set by the government and is used to measure the efficiency of air purification and filtration systems.

IONIZERS: Ionizers use high voltage electricity to electrically charge air molecules and create negative electrons. The negative ions charge small particles that clump together and become too heavy to remain airborne. These charged particles end up sticking to any surface available. This process often creates ozone as a dangerous byproduct.

MERV: Minimum Efficiency Reporting Value is a number from 1 to 16 that is relative to an air filter's efficiency. The higher the MERV, the more efficient the air filter is at removing particles. At the lower end of the efficiency spectrum a fiberglass panel filter may have a MERV of 4 or 5. At the higher end, a MERV 14 filter is typically the filter of choice for critical areas of a hospital to prevent the transfer of bacteria and infectious disease. Higher MERV filters are also capable of removing higher quantities of extremely small contaminants. A higher MERV creates more resistance to airflow because the filter media becomes denser as efficiency increases.

MOLD: A group of organisms that belong to the kingdom Fungi. In this course, the terms fungi and mold are used interchangeably.

mVOC (MICROBIAL VOLATILE ORGANIC COMPOUND): A chemical made by mold that is a gas at room temperature and may have a moldy or musty odor.

MULTIPLE CHEMICAL SENSITIVITY (MCS): MCS is an unusually severe sensitivity to many different pollutants including solvents, VOC's, perfumes, diesel, smoke and chemicals in general. Studies show that MCS is more common in women than men and most often in younger adults between the ages of 30 and 50.

MYCOTOXIN: A toxin produced by a mold.

NEGATIVE PRESSURE: A 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. Under this condition, if an opening exists, air will flow from surrounding areas into the negatively pressurized space.

ODOR: A quality of gases, liquids, or particles that stimulates the olfactory organ or sense of smell.

OFF-GASSING: Off-gassing is the evaporation of volatile chemicals in non-metallic materials at normal atmospheric pressure. Materials such as paints, stains and varnishes can produce significant off-gassing in your home or office. The off-gassing of Volatile Organic Compounds (VOCs) seriously affect the quality of air indoors.

OZONE: An unstable, poisonous allotrope of oxygen that is formed naturally in the ozone layer from atmospheric oxygen by electric discharge or exposure to ultraviolet radiation, also produced in the lower atmosphere by the photochemical reaction of certain pollutants.

OZONE GENERATORS: Appliances that use UV lamps or electrical discharges to produce ozone that reacts with chemical and biological pollutants and transforms them into harmless substances. Ozone is a potent lung irritant, which in concentrations that do not exceed public health standards, has little potential to remove indoor air contaminants. Thus ozone generators are not always safe and effective in controlling indoor air pollutants.

PARTICULATE MATTER: Particulate matter is composed of microscopic solids, liquid droplets, or a mixture of solids and liquid droplets suspended in air. Also known as particle pollution, it is made up of a number of components, including acids such as nitric and sulfuric acids, organic chemicals, metals, soil or dust particles, and biological contaminants.

PET DANDER: Pet dander is the tiny scales of an animal's dead skin that is shed. Pet Dander can float in the air for a long time before sticking to a surface allowing it to be spread widely around a home.

PHOTOCATALYTIC OXIDATION (PCO): A process that exposes UV light to a catalyst such as titanium dioxide (tiO2) to produce radicals, which can oxidize or break down typical VOCs, viruses, bacteria and mold, and are commonly used in conjunction with particle filters such as HEPA filters.

PPM: Parts Per Million.

PRE-FILTER: A pre-filter captures larger particles before other filtration steps to help extend the life of the HEPA filter.

PRESSED WOOD PRODUCTS: A group of materials used in building and furniture construction that are made from wood veneers, particles, or fibers bonded together with an adhesive under heat and pressure.

SICK BUILDING SYNDROME (SBS): Term that refers to a set of symptoms that affect some number of building occupants during the time they spend in the building and diminish or go away during periods when they leave the building. Cannot be traced to specific pollutants or sources within the building. (Contrast with "Building related illness"). Term sometimes used to describe situations in which building occupants experience acute health and/or comfort effects that appear to be linked to time spent in a particular building, but where no specific illness or cause can be identified. The complaints may be localized in a particular room or zone, or may be spread throughout the building.

SPORE: The means by which molds reproduce. Spores are microscopic. They vary in shape and range from 2 to 100 microns in size. Spores travel in several ways: passively moved by a breeze or water drop, mechanically disturbed (by a person or animal passing by), or actively discharged by the mold (usually under moist conditions or high humidity).

TOXIGENIC: Producing toxic substances.

UV: Ultraviolet.

UVGI: Ultraviolet germicidal irradiation.

VENTILATION RATE: The rate at which outdoor air enters and leaves a building. Expressed in one of two ways: the number of changes of outdoor air per unit of time (air changes per hour, or "ACH") or the rate at which a volume of outdoor air enters per unit of time (cubic feet per minute, or "CFM").

VINYL CHLORIDE: A chemical compound, used in producing some plastics, that is believed to be oncogenic.

VIRUS: The smallest form of microorganisms capable of causing disease.

VOLATILE ORGANIC COMPOUNDS (VOCs): Compounds that vaporize (become a gas) at room temperature. Common sources which may emit VOCs into indoor air include housekeeping and maintenance products, and building and furnishing materials. 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. They can be emitted by a wide range of products found around the home such as paints and lacquers, cleaning supplies, pesticides and building materials, office equipment such as copiers and printers, correction fluids and carbonless copy paper, graphics and craft materials including glues and adhesives, permanent markers, and photographic solutions. Pollution indoors can be up to five times worse than pollution outdoors, due to high levels of VOCs.