Glossary of IAQ Terms
Absorption – The physiological process by which toxicants pass body membranes and enter the bloodstream or other body components from the site of exposure.
ACH – Air changes per hour. One ACH means a volume of outdoor air equal to the volume of the space being ventilated has entered that space in one hour.
Animal dander – Tiny scales of animal skin.
Antagonistic effect – A biological response to exposure to a single chemical interfering with the action of another or to multiple chemicals interfering with each other’s actions.
Antimicrobial – Agent that kills microbial growth. See disinfectant, sanitizer, and sterilizer.
ASHRAE – American Society of Heating, Refrigeration, and Air Conditioning Engineers.
Asphyxiants – Substances that starve the cells of an individual from the life-giving oxygen needed to sustain metabolism.
Bacteria – Microorganisms that have no true nucleus, a single chromosome, and no mitochondria, capable of causing adverse health effects.
Bake-out – A process whereby an unoccupied building is maintained at elevated temperatures to enhance the emission of VOCs prior to the occupation of the building, in the theory that the VOCs will be ventilated out of the building. This practice is controversial and not without risk of incurring other types of problems.
Bioaerosols – Tiny airborne particles that are alive, were once alive, or are a part of something that is or once was alive.
Biocide – a physical or chemical agent that is capable of killing microorganisms.
Biofilm – a surface layer of microorganisms.
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.
Breathing Zone – Area of a room in which occupants breathe as they stand, sit, or lie down.
BRI – See Building-Related illness
Bronchi – The two respiratory tubes branching into the two lungs at the lower end of the trachea. They branch into progressively smaller passageways, the bronchioles, and finally reach the alveoli, the location where gas exchange occurs.
Building Envelope – Elements of the building, including all external building materials, windows, and walls, that enclose the internal space.
Building-related illness – A discrete, identifiable disease or illness that can be traced to a specific pollutant or source within a building. (e.g., Legionnaires’ disease, hypersensitivity pneumonitis) (Contrast with sick building)
Calibration – The comparison of an instrument response to known values of a parameter being measured.
CAV – See Constant Air Volume.
Ceiling Plenum – Space below the flooring and above the suspended ceiling that accommodates the mechanical and electrical equipment and is used as part of the air distribution system. The space is kept under negative pressure.
CENTRAL AIR HANDLING UNIT (Central AHU)- This is the same as an Air Handling Unit, but serves more than one area.
CFM – Cubic feet per minute.
Chemical sensitivity – Health problems characterized by effects such as dizziness, eye and throat irritation, chest tightness, and nasal congestion that appear whenever individuals are exposed to certain chemicals. People may react to even trace amounts of chemicals to which they have become sensitized.
Clean – visually free of sludge, sediment, slime, algae, fungi, rust and scale.
Cleaning – physical and/or chemical removal of scale, corrosion, biofilm, sludge, sediment and extraneous matter.
CO – Carbon monoxide.
CO2 – Carbon dioxide.
Colony Forming Unit (cfu) – a colony arising from a viable unit of one bacterium or more in a clump. For statistical significance, only those plates with 30 to 300 cfu’s are selected for counting.
Conditioned air – Air that has been heated, cooled, humidified, or dehumidified to maintain an interior space within the comfort zone. (Sometimes referred to as tempered air.)
Constant Air Volume (CAY) System – Refers to a type of HVAC system where air volume is constant and airstream is either heated or cooled so as to maintain a constant temperature.
Constant volume systems – Air handling systems that are designed to provide constant airflow and vary air
Criteria Air Pollutants – Include sulfur dioxide, particulates, lead, ozone, nitrogen oxides, and carbon monoxide, all designated by the EPA and which have national standards under the National Ambient Air Quality Standards (NAAQS).
Dampers – Controls that vary airflow through an air outlet, inlet, or duct. A damper position may be immovable, manually adjustable, or part of an automated control system.
Detergent – a cleansing agent capable of penetrating biological films, sludge and sediment and having the ability to emulsify oil and hold materials in suspension. Water treatment specialist have developed detergent formulations which are capable of thoroughly cleaning components which are difficult to access and inspect, such as cooling tower fill.
Diffusers and grilles – Ventilation system components that distribute and diffuse air at various points in the ventilation system. Diffusers (supply) and grilles (return) are arranged to promote air circulation.
Diffusion – Movement of molecules (gases and some liquids) from a region of higher concentration to a region of lower concentration.
Dilution – additional air beyond that which is needed to provide combustion. This may either be within the combustion chamber as excess air or as induced flow in the exhaust stack.
Disinfectants – One of three groups of antimicrobials registered by EPA for public health uses. EPA considers an antimicrobial to be a disinfectant when it destroys or irreversibly inactivates infectious or other undesirable organisms, but not necessarily their spores. EPA registers three types of disinfectant products based upon submitted efficacy data: limited, general or broad spectrum, and hospital disinfectant.
Dust spot efficiency – A measure (expressed in percent) of the ability of a filter to remove atmospheric dust from air.
Environmental Agents – 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 overcrowding).
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.
Epidemiology – The study of the incidence, distribution, and control of disease in a population.
Exhaust – air removed form the house through fans. Typical examples are bathroom exhaust, and kitchen hoods.
Exhaust ventilation – Mechanical removal of air from a portion of a building (e.g., piece of equipment, room, or general area).
Exposure – The initial contact of the body with a substance.
Exposure assessment – Analysis of a set of exposure profiles which address for each pollutant, the size of the exposed population, and the routes, duration, frequencies, and intensities of exposure.
False negative – Test or investigation results that indicate a particular condition does not exist when it actually does.
False positive – Test or investigation results that incorrectly indicate the existence of a particular condition.
FIFRA – Federal Insecticide, Fungicide, and Rodenticide Act.
Fumes – Refers to solid particles generated by condensation of vapors or gases, generally after volatilization from combusted melted substances. Popular usage sometimes loosely includes any type of contaminant.
Fungi – Any of a group of parasitic lower plants, including molds and mildews, that lack chlorophyll.
Gases – Individual atoms or molecules that spread evenly throughout a volume of air, and cannot be collected by ordinary particulate filters.
Hazardous Air Pollutants – 189 chemicals considered by the EPA to be hazardous to human health.
HEPA – High efficiency particulate arrestance (filters).
Humidifier – A device to add moisture to air.
Humidifier fever – A respiratory illness that may be caused by exposure to toxins from microorganisms found in wet or moist areas of humidifiers and air conditioners. Also called air conditioner fever or ventilation fever.
HVAC – Acronym for heating, ventilating, and air conditioning system.
Hydronic Heat – Heat transferred from a boiler, to conditioned water, to a radiator in the living space. (Called hydropic because water [hydro-] is the medium of heat transfer.)
IAQ – Indoor air quality.
IAQ BACKGROUNDER – A component of the IAQ Tools for Schools Kit that provides a general introduction to IAQ issues, as well as IAQ program implementation information.
IAQ COORDINATOR – An individual at the school and/or school district level who provides leadership and coordination of IAQ activities.
IAQ CHECKLIST – A component of the IAQ Tools for Schools Kit containing information and suggested easy-to-do activities for school staff to improve or maintain good indoor air quality. Each Activity Guide focuses on topic areas and actions that are targeted to particular school staff (e.g., Teacher’s Checklist, Administrative Staff Checklist, Health Officer’s Checklist, Ventilation Checklist, Building Maintenance Checklist, Food Service Checklist, Waste Management Checklist, Renovation and Repair Checklist and Walkthrough Checklist) or specific building functions (e.g., HVAC system, roofing, renovation, etc.). The Checklists are to be completed by the staff and returned to the IAQ Coordinator as a record of activities completed and assistance as requested.
IAQ INFO – EPA’s Indoor Air Quality Information Clearinghouse (1-800-438-4318 or 301-585-9020)
IAQ MANAGEMENT PLAN – A component of the IAQ Tools for Schools Kit, specifically, a set of flexible and specific steps for preventing and resolving IAQ problems.
IAQ TEAM – People who have a direct impact on IAQ in the schools (school staff, administrators, school board members, students and parents) and who
Irritants – Substances that inflame living tissue by chemical action at the site of contact, causing pain or swelling.
Legionnaires’ disease – An illness which is sometimes fatal and whose symptoms mimic pneumonia. It is caused by a bacterium (Legionnella pneumophila) and primarily attacks immunocompromised individuals.
Macrophage – A large phagocytic cell found in the lung tissues that helps defend the body against viruses, bacteria, and other foreign intruders, generally by engulfing them.
Make up – Air which enters the house, either intended or not, to replace the air removed through exhaust and dilution.
Make-up Air – Air brought into a building from the outdoors through the ventilation system, which has not been previously circulated through the system.
Management – Operation of an IAQ program-including personnel and budgeting decisions, monitoring and feedback, legislative initiatives, internal information flows, and enforcement of State requirements.
mg/L (ppm) – milligrams per liter (parts per million). For practical purposes mg/L is assumed to be equal to ppm.
MODEL BUILDING CODES – The building codes published by the 4 Model Code Organizations and commonly adopted by state or other jurisdictions to control local construction activity.
Mold – Growth produced by any of a large group of fungi that has a cottony or furry appearance.
MSDS – Material Safety Data Sheet.
Mutagens – Substances that induce a permanent change in the genetic material.
Mycotoxins – Metabolites produced by fungi that have a broad spectrum of toxic effects ranging from mild acute toxicity to potent carcinogenicity.
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.
NIOSH – National Instititute for Occupational Safety and Health (U.S.A.)
Occupational Standards – Maximum pollutant concentration levels, usually set by the Occupational Safety and Health Administration (OSHA).
Off-gassing – The production of gases from the chemical deterioration of a substance over time.
Organic compounds – Chemicals that contain carbon. Volatile organic compounds vaporize at room temperature and pressure and are found in many indoor sources including many common household products and building materials.
OSHA – Acronym for the Occupational Safety and Health Administration, a part of the U.S. Department of Labor responsible for determining whether employers are providing working conditions that are safe for employees.
OUTDOOR AIR SUPPLY – Air brought into a building from the outdoors (often through the ventilation system) that has not been previously circulated through the system. Also known as “Make-Up Air.”
Particles – Solids or liquids light enough to be suspended in air.
Pathogens – Disease-producing microorganisms or materials.
PELs – Permissible Exposure Limits (standards set by OSHA), workplace exposure limits established to protect on-the-job workers.
Plenum – An air compartment connected to a duct or ducts.
Pollutant pathways – The routes followed by a pollutant from its emission (source) as it travels through a structures, air streams, etc.
Positive Pressure – Condition that exists when more air is supplied to a space than is exhausted, so that air pressure within that space is greater than that found in surrounding areas.
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.
PRESSURE, STATIC – In flowing air, the total pressure minus velocity pressure. The portion of the pressure that pushes equally in all directions.
PRESSURE, TOTAL – In flowing air, the sum of the static pressure and the velocity pressure.
PRESSURE, VELOCITY – In flowing air, the pressure due to the velocity and density of the air.
Public information – Development and dissemination of both technical and non-technical IAQ information to homeowners, private companies, the media, local officials, and other concerned parties.
QA/QC – Quality Assurance/Quality Control procedures are used to assess method performance, accuracy, and precision.
Radon – A radioactive gas formed by the decay of uranium.
Re-entrainment – Situation that occurs when the air being exhausted from a building is immediately brought back into the system through the air intake and other openings in the building envelope.
RELs – Recommended Exposure Limits (recommendations made by NIOSH)Respirable Particles – Those particles found in air that are capable of penetrating and being deposited in the deeper (non-ciliated) portion of the lung.
Risk Assessment – Broadly defined as the scientific activity of evaluating the toxic properties of a substance and its potentials for human exposure, to determine the probability of exposed humans being adversely affected.
Sanitizer – One of three groups of antimicrobials registered by EPA for public health uses.’ EPA considers an antimicrobial to be a sanitizer when it reduces, but does not necessarily eliminate, all the microorganisms on a treated surface. To be a registered sanitizer, the test results for a product must show a reduction of at least 99.9% in the number of each test microorganisms over the parallel control.
SARA – Acronym for the Superfund Amendments and Reauthorization Act of 1986. Title IV of this Act requires EPA to establish a research program for radon gas and IAQ and to disseminate information on IAQ problems and solutions based on current research.
SBS – See Sick Building Syndrome.
Sick Building Syndrome – Term that refers to a set of symptoms affecting a 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.)
Sodium Hypochlorite – a chlorine-releasing material used for disinfection. The strength of sodium hypochlorite solution reduces on storage.
Soil Gases – Gases that enter a building from the surrounding ground (e.g., radon, volatile organics, pest ticides)
Source emissions – Emissions generated at the origin of a pollutant.
Standards – Usually, mandatory guidance which is founded on statutory authority and involves an enforcement program; however, sometimes used to refer to nonregulatory guidance (e.g., ASHRAE ventilation standards).
Static Pressure – Condition that exists when an equal amount of air is supplied to and exhausted from a space. At static pressure, equilibrium has been reached.
Sterilizer – One of three groups of antimicrobials registered for public health uses. EPA considers an antimicrobial to be a sterilizer when it destroys or eliminates all forms of bacteria, fungi, viruses, and their spores. Because spores are considered the most difficult form of a microorganism to destroy, EPA considers the term sporicide to be synonymous with sterilizer.
Surfactant – a soluble surface-acting agent that reduces surface tension between particulate matter and water.
TEAM Studies – Acronym for Total Exposure Assessment Methodology Studies. The goal of these long-term series of EPA-conducted studies is to determine the actual exposure of people to a substance or substances.
Threshold – The lowest dose of a chemical at which a specific measurable effect is observed. Below this dose, the effect is not observed.
Total Bacteria Count (TBC) – an estimate of the number of viable units of bacteria per milliliter of water under the conditions of testing. Note that no single method, culture medium or conditions of incubation can satisgy the growth requirements of all bacteria in a water sample.
Toxic – Harmful, poisonous.
Toxic Air Pollutants – Aggregate emissions of the following are determined by the EPA to be toxic -Benzene, 1,3 Butadiene, Polycyclic Organic Matter, Acetaldehyde, Formaldehyde.
Toxicity – The innate ability of a contaminant to cause injury to biological tissue.
Toxicology – The study of the adverse effects of chemicals on living organisms.
Tracer Gases – Compounds, such as sulfur hexafluoride, which are used to identify suspected pollutant pathways and quantify ventilation rates. Tracer gases may be detected qualitatively by their odor or quantitatively by means of air monitoring equipment.
Turbidity – a cloudy appearance in water that is caused by a suspension of colloidal or particulate matter.
TVOCs – Total volatile organic compounds.
Vapors – Vapors represent the gaseous phase of a substance that is normally liquid or solid at room temperature and atmospheric pressure.
Variable Air Volume (VAV) systems – Air handling systems designed to condition air to a constant temperature and vary airflow to ensure thermal comfort.
Ventilation – a minimum amount of air required for IAQ and moisture control. This may be natural through leaks and infiltration or controlled in a tight house through a heat exchanger.
Ventilation Air – Defined as the total air, which is a combination of the air brought into a system from the outdoors and the air that is being recirculated within the building. (Sometimes used to refer only to air brought into a system from the outdoors.)
Ventilation Rate – The rate at which outside air replaces indoor air (also referred to as air exchange rate), expressed in one of two ways-the number of changes of outside air per hour (ACH), or the rate at which a volume of outside air enters per unit of time (cubic feet per minute, or cfm).
Viruses – The smallest of all life forms containing either RNA or DNA. Viruses are responsible for a variety of human infections.
VOCs – See Volatile Organic Compounds.
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 know about what health effects occur at the levels of VOCs typically found in public and commercial buildings.
WHO – Acronym for the World Health Organization.