AHERA: Asbestos Hazard Emergency response Act
AQI: The Air Quality Index is a tool that provides the public with clear and timely information on local air quality and whether air pollution levels pose a health concern.
ASHRAE: American Society of Heating, Refrigerating, and Air-Conditioning Engineers. See Appendix L: Resources for more information.
ASTM: Consensus standard-setting organization. See Appendix L: Resources for more information.
After treatment Device: Engine pollutant emissions are generally reduced by engine modifications, fuel specifications, or exhaust gas after treatment. An after treatment device is a component used to reduce engine pollutant emissions downstream of the combustion chamber. Catalytic converters and particulate filters are examples of after treatment devices.
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 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 — cubic feet per minute (cfm).
Air Handling Unit, or AHU: For purposes of this document, refers to equipment that includes a blower or fan, heating and/or cooling coils, and related equipment such as controls, condensate drain pans, and air filters. Does not include ductwork, registers and grilles, or boilers and chillers.
Air Toxics: Chemicals in the air that are known or suspected to cause cancer or other serious health effects, such as reproductive problems or birth defects. Air toxics are also known as "hazardous air pollutants." Mobile sources emit a number of air toxics associated with both long-term and short-term health effects in people, including heart problems, asthma symptoms, eye and lung irritation, cancer, and premature death.
Alternative Fuel: An alternative fuel is any fuel other than gasoline and diesel fuels, such as methanol, ethanol, compressed natural gas, and other gaseous fuels. Generally, alternative fuels burn more cleanly and result in less air pollution.
Antimicrobial: Agent that kills microbial growth. See disinfectant; sanitizer; and sterilizer.

Top of page

Benzene: A cancer-causing hydrocarbon (C6H6) derived from petroleum. Benzene is a component of gasoline. Benzene emissions occur in exhaust as a byproduct of fuel combustion and when gasoline evaporates.
Biological Contaminants: Biological contaminants are or are produced by living organisms. Common biological contaminants include mold, dust mites, pet dander (skin flakes), droppings and body parts from cockroaches, rodents and other pests, or insects, viruses, and bacteria. Biological contaminants 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. See Appendix E: Typical Indoor Air Pollutants for more information.
Building-Related Illness, or BRI: Diagnosable illness with identifiable symptoms for which the cause can be directly attributed to airborne building pollutants (e.g., Legionnaire’s disease, hypersensitivity pneumonitis).

Top of page

Central Air Handling Unit, or Central AHU: For purposes of this document, this is the same as an Air handling unit, but serves more than one area.
CFM: Cubic feet per minute. The amount of air, in cubic feet, that flows through a given space in one minute. 1 CFM equals approximately 2 liters per second (L/s).
CO: Carbon monoxide. See Appendix E: Typical Indoor Air Pollutants for more information.
CO₂: Carbon dioxide. See Appendix B: Basic Measurement Equipment and Appendix E: Typical Indoor Air Pollutants for more information.
Combustion: The process of burning. Motor vehicles and equipment typically burn fuel in an engine to create power. Gasoline and diesel fuels are mixtures of hydrocarbons, which are compounds that contain hydrogen and carbon atoms. In "perfect" combustion, oxygen in the air would combine with all the hydrogen in the fuel to form water and with all the carbon in the fuel to form carbon dioxide. Nitrogen in the air would remain unaffected. In reality, the combustion process is not "perfect," and engines emit several types of pollutants as combustion byproducts.
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.)

Top of page

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.
Diesel Engine: An engine that operates on diesel fuel and principally relies on compression-ignition for engine operation. The non-use of a throttle during normal operation is indicative of a diesel engine.
Diffusers and Grilles: Components of the ventilation system that distribute and return air to promote air circulation in the occupied space. As used in this document, supply air enters a space through a diffuser or vent and return air leaves a space through a grille.
Disinfectants: One of three groups of antimicrobials registered by EPA for public health concerns. A disinfectant destroys or irreversibly inactivates undesirable (and often infectious) organisms. EPA registers three types of disinfectant products based upon submitted efficacy data: limited, general/broad spectrum, and hospital disinfectant.
Drain Trap: A dip in the drain pipe of sinks, toilets, floor drains, etc., which is designed to stay filled with water, thereby preventing sewer gases from escaping into the room.

Top of page

Emissions: Releases of pollutants into the air from a source, such as a motor vehicles, furnishings, or cleaning products.
Emissions Standards: Rules and regulations that set limits on how much pollution can be emitted from a given source. Vehicle and equipment manufacturers have responded to many mobile source emissions standards by redesigning vehicles and engines to reduce pollution.
EPA: United States Environmental Protection Agency. See Appendix L: Resources for more information.
ETS: Environmental tobacco smoke. Mixture of smoke from the burning end of a cigarette, pipe, or cigar and smoke exhaled by the smoker (also secondhand smoke or passive smoking). See Appendix E: Typical Indoor Air Pollutants and Appendix F: Secondhand smoke and Appendix L: Resources for more information.
Evaporation: The process by which a substance is converted from a liquid to a vapor. "Evaporative emissions" occur when a liquid fuel evaporates and fuel molecules escape into the atmosphere. A considerable amount of hydrocarbon pollution results from evaporative emissions that occur when gasoline leaks or spills, or when gasoline gets hot and evaporates from the fuel tank or engine.
Exhaust Ventilation: Mechanical removal of air from a building.

Top of page

Fine Particulate Matter (PM_2.5 or PM fine): Tiny particles or liquid droplets less than 2.5 microns in diameter suspended in the air that can contain a variety of chemical components. PM fine particles are so small that they are not typically visible to the naked eye. These tiny particles can be suspended in the air for long periods of time and are the most harmful to human health because they can penetrate deep into the lungs. Some particles are directly emitted into the air. Virtually all particulate matter from mobile sources is PM_2.5. See Appendix E: Typical Indoor Air Pollutants for more information.
Flow Hood: Device that easily measures airflow quantity, typically up to 2,500 cfm.

Top of page

Highway Engine: Any engine that is designed to transport people or property on a street or highway.
HVAC: Heating, ventilation, and air-conditioning system.
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.

Top of page

IAQ: Indoor air quality.
IAQ Backgrounder: A general introduction to IAQ issues as well as IAQ program implementation information that accompanies the IAQ checklists.
IAQ Checklist: A list of suggested easy-to-do activities for school staff to improve or maintain good indoor air quality. Each focuses on topic areas and actions that are targeted to particular school staff (e.g., teachers, administrators, kitchen staff, maintenance staff) or specific building functions (e.g., HVAC system, roofing, renovation). The checklists are to be completed by the staff and returned to the IAQ Coordinator as a record of completed activities and requested assistance.
IAQ Coordinator: An individual at the school and/or school district level who provides leadership and coordination of IAQ activities. See Section 2: Role and Functions of the IAQ Coordinator in the IAQ Coordinator's Guide for more information.
Indoor Air Pollutant: Particles and dust, fibers, mists, bioaerosols, and gases or vapors. See Section 2: Understanding IAQ Problems and Appendix E: Typical Indoor Air Pollutants for more information.
IPM: Integrated Pest Management. A comprehensive approach to eliminating and preventing pest problems with an emphasis on reducing pest habitat and food sources. See Appendix B: Developing Indoor Air Policies in the IAQ Coordinator's Guide and Appendix K: Integrated Pest Management for more information.

Top of page

Make-up Air: See Outdoor Air Supply.
Microbiologicals: See Biological Contaminants.
Mobile Sources: Motor vehicles, engines, and equipment that move, or can be moved, from place to place. Mobile sources include vehicles that operate on roads and highways ("on-road" or "highway" vehicles), as well as nonroad vehicles, engines, and equipment. Examples of mobile sources are cars, trucks, buses, earth-moving equipment, lawn and garden power tools, ships, railroad locomotives, and airplanes.
Multiple Chemical Sensitivity, or MCS: A condition in which a person reports sensitivity or intolerance (as distinct from "allergic") to a number of chemicals and other irritants at very low concentrations. There are different views among medical professionals about the existence, causes, diagnosis, and treatment of this condition.

Top of page

NIOSH: National Institute for Occupational Safety and Health. See Appendix L: Resources for more information.
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. Under this condition, if an opening exists, air will flow from surrounding areas into the negatively pressurized space.
Nonroad Engine: A term that covers a diverse collection of engines, equipment, vehicles, and vessels. Sometimes referred to as "off-road" or "off-highway," the nonroad category includes garden tractors, lawnmowers, bulldozers, and cranes. Although nonroad engines can be self-propelled, their primary function is to perform a particular task. See Appendix I: Mobile Sources for more information.

Top of page

OSHA: Occupational Safety and Health Administration. See Appendix L: Resources for more information.
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.
Oxidation Catalyst: A type of catalyst (catalytic converter) that chemically converts hydrocarbons and carbon monoxide to water vapor and carbon dioxide.

Top of page

Particulate Filter/Trap: An after treatment, anti-pollution device designed to trap particles in diesel particulate matter from engine exhaust before they can escape into the atmosphere.
Particulate Matter 2.5 (PM_2.5): See Fine Particulate Matter
Plenum: Unducted air compartment used to return air to central air handling unit.
Pollutant Pathways: Avenues for distribution of pollutants in a building. HVAC systems are the primary pathways in most buildings; however, all building components and occupants interact to affect how pollutants are distributed. See Section 2: Understanding IAQ Problems for more information.
Pollutants (Pollution): Unwanted chemicals or contaminants found in the environment. Pollutants can harm human health, the environment, and property. Air pollutants occur as gases, liquid droplets, and solids. Once released into the environment, many pollutants can persist, travel long distances, and move from one environmental medium (e.g., air, water, land) to another.
Polychlorinated Biphenyls (PCBs): Mixtures of synthetic organic chemicals with the same basic chemical structure and similar physical properties ranging from oily liquids to waxy solids. PCBs were used in hundreds of industrial and commercial applications including electrical, heat transfer, and hydraulic equipment; as plasticizers in paints, plastics, and rubber products; in pigments, dyes, and carbonless copy paper, and many other applications. Production of PCBs in the United States ceased in 1977.
Positive Pressure: Condition that exists when more air is supplied to a space than is exhausted, so the air pressure within that space is greater than that in surrounding areas. Under this condition, if an opening exists, air will flow from the positively pressurized space into surrounding areas.
PPM: Parts per million.
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: The pressure due to the air flow rate and density of the air.
Preventive Maintenance: Regular and systematic inspection, cleaning, and replacement of worn parts, materials, and systems. Preventive maintenance helps to prevent parts, material, and systems failure by ensuring that parts, materials, and systems are in good working order.
Psychogenic Illness: This syndrome has been defined as a group of symptoms that develop in an individual (or a group of individuals in the same indoor environment) who are under some type of physical or emotional stress. This does not mean that individuals have a psychiatric disorder or that they are imagining symptoms.

Top of page

Radon

A colorless, odorless gas that occurs naturally in almost all soil and rock. Radon migrates through the soil and groundwater and can enter buildings through cracks or other openings in the foundation. Radon can also enter through well water. Exposure to radon can cause lung cancer. See Appendix G: Radon and Appendix E: Typical Indoor Air Pollutants for more information.

Re-entry

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.

Retrofit

An engine "retrofit" includes (but is not limited to) any of the following activities:

Addition of new/better pollution control after treatment equipment to certified engines.
Upgrading a certified engine to a cleaner certified configuration.
Upgrading an uncertified engine to a cleaner "certified-like" configuration.
Conversion of any engine to a cleaner fuel.
Early replacement of older engines with newer (presumably cleaner) engines (in lieu of regular expected rebuilding).
Use of cleaner fuel and/or emissions reducing fuel additive (without engine conversion).

Top of page

Sanitizer: One of three groups of anti-microbials 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 percent in the number of each test microorganism over the parallel control.
Secondhand Smoke: See Appendix F: Secondhand Smoke for more information.
Short-circuiting: Situation that occurs when the supply air flows to return or exhaust grilles before entering the breathing zone (area of a room where people are). To avoid short-circuiting, the supply air must be delivered at a temperature and a velocity that result in mixing throughout the space.
Sick Building Syndrome, or SBS: 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.
Soil Gases: Gases that enter a building from the surrounding ground (e.g., radon, volatile organic compounds, gases from pesticides in the soil).
Sources: Sources of indoor air pollutants. Indoor air pollutants can originate within the building or be drawn in from outdoors. Common sources include people, room furnishings such as carpeting, photocopiers, art supplies, etc. See Section 5: Diagnosing IAQ Problems for more information.
Stack Effect: The flow of air that results from warm air rising, creating a positive pressure area at the top of a building and a negative pressure area at the bottom of a building. In some cases the stack effect may overpower the mechanical system and disrupt ventilation and circulation in a building.
Sterilizer: One of three groups of anti-microbials registered by EPA 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."

Top of page

TVOCs: Total volatile organic compounds. See "Volatile Organic Compounds (VOCs)."

Top of page

ULSD: Ultra-low Sulfur Fuel. The manufacturers of retrofit technologies, which reduce sulfur emissions, specify the maximum allowable sulfur level for effective operation of its products. For the purposes of the diesel retrofit program, diesel fuel must contain less than 15 ppm sulfur to be considered as ultra-low sulfur fuel. The use of ultra-low sulfur fuel alone can reduce emissions of particulate matter. Sulfate, a major constituent of particulate matter, is produced as a byproduct of burning diesel fuel containing sulfur. Reducing the sulfur content of fuel, in turn, reduces sulfate byproducts of combustion and, therefore, particulate matter emissions.
Unit Ventilator: A single fan-coil unit designed to satisfy tempering and ventilation requirements for individual rooms.

Top of page

Ventilation Air: Defined as the total air, which is a combination of the air brought inside from outdoors and the air that is being recirculated within the building. Sometimes, however, used in reference only to the air brought into the system from the outdoors; this document defines this air as "outdoor air ventilation."
Volatile Organic Compounds, or VOCs: Compounds are a gas at room temperature. Common sources that 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. At present, not much is known about what health effects occur at the levels of VOCs typically found in public and commercial buildings. See Appendix E: Typical Indoor Air Pollutants for more information.

Top of page

Zone: The occupied space or group of spaces within a building that has its heating or cooling controlled by a single thermostat.

Top of Page

<< Go back to the Table of Contents | Go back to Appendix L >>

IAQ Tools for Schools Action Kit IAQ Design Tools for Schools Develop Your Program Health and Achievement

Technical Solutions Academic Performance Asthma Case Studies

IAQ Champions Webinars E-Newsletters Multimedia

Connect to the Network Publications/Resources Lesson Plans Indoor Air Quality

School and District Officials | Teachers and Students | Facilities Staff | Parents | Health Care Professionals

IAQ Reference Guide

Appendix M - Glossary and Acronyms

Area Navigation