Glossary of Terms
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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.
ACTION LEVEL: A term used to identify the
level of indoor radon at which remedial action is
recommended. (EPA's current action level is 4 pCi/L.)
ACTION PACKET: In reference to the
IAQ Tools for Schools Action Kit - contains numerous products to assist school personnel to implement an
effective yet simple IAQ program in their school.
AHU: See "Air
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
(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 or grilles, or boilers and chillers.
AIR PASSAGES: Openings through or within
walls, through floors and ceilings, and around chimney flues and plumbing
chases, that permit air to move out of the conditioned spaces of the building.
ANIMAL DANDER: Tiny scales of animal skin.
ALLERGEN: A substance capable of causing
an allergic reaction because of an individual's sensitivity to that substance.
ALLERGIC RHINITIS: Inflammation of the
mucous membranes in the nose that is caused by an allergic reaction.
ANTIMICROBIAL: Agent that kills microbial
growth. See "disinfectant," "sanitizer," and
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." Read More...
BREATHING ZONE: Area of a room in which
occupants breathe as they stand, sit, or lie down.
BUILDING ENVELOPE: Elements of the
building, including all external building materials, windows, and walls, that
enclose the internal space.
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
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CEILING PLENUM: Space below the flooring
and above the suspended ceiling that accommodates the mechanical and electrical
equipment and that 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. 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).
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."
CO: Carbon monoxide. Read More...
CO2: Carbon dioxide.
COMBINATION FOUNDATIONS: Buildings
constructed with more than one foundation type; e.g., basement/crawlspace or
COMMISSIONING: Start-up of a building that
includes testing and adjusting HVAC, electrical, plumbing, and other systems to
assure proper functioning and adherence to design criteria. Commissioning also
includes the instruction of building representatives in the use of the building
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 SYSTEMS: Air handling
system that provides a constant air flow while varying the temperature to meet
heating and cooling needs.
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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.
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 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.
DRAIN TILE LOOP: A
continuous length of drain tile or perforated pipe extending around all or part
of the internal or external perimeter of a basement or crawlspace footing.
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.
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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
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). Read More...
ERGONOMICS: Applied science that
investigates the impact of people's physical environment on their health and
comfort (e.g., determining the proper chair height for computer operators).
EXHAUST VENTILATION: Mechanical removal of
air from a portion of a building (e.g., piece of equipment, room, or general
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FLOW HOOD: Device that easily measures
airflow quantity, typically up to 2,500 cfm.
FUNGI: Any of a group of parasitic lower
plants that lack chlorophyll, including molds and mildews.
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GAS SORPTION: Devices used to reduce
levels of airborne gaseous compounds by passing the air through materials that
extract the gases. The performance of solid sorbents is dependent on the airflow
rate, concentration of the pollutants, presence of other gases or vapors, and
GOVERNMENTAL: In the case of building
codes, these are the State or local organizations/agencies responsible for
building code enforcement.
Green Buildings: The
building industry is increasingly focused on making its buildings greener,
which includes using healthier, less polluting and more resource-efficient
practices. Indoor environmental quality (IEQ) refers to the
quality of the air and environment inside buildings, based on pollutant
concentrations and conditions that can affect the health, comfort and
performance of occupants -- including temperature, relative humidity, light,
sound and other factors. Good IEQ is an essential component of any building,
especially a green building.
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HEPA: High efficiency particulate
HUMIDIFIER FEVER: A respiratory illness
caused by exposure to toxins from microorganisms found in wet or moist areas in
humidifiers and air conditioners. Also called air conditioner or ventilation
HVAC: Heating, ventilation, and
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.
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IAQ: Indoor air quality.
BACKGROUNDER: A component of the IAQ
Tools for Schools Action Kit that provides a general introduction to IAQ
issues, as well as IAQ program implementation information.
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 Action 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. 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 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 implement the IAQ Action Packets.
IPM: Integrated pest management.
INDICATOR COMPOUNDS: Chemical compounds,
such as carbon dioxide, whose presence at certain concentrations may be used to
estimate certain building conditions (e.g., airflow, presence of sources).
INDOOR AIR POLLUTANT: Particles and dust,
fibers, mists, bioaerosols, and gases or vapors.
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MAKE-UP AIR: See "Outdoor
MAP OF RADON
ZONES: A U.S. EPA publication depicting areas of differing
radon potential in both map form and in state specific booklets.
MCS: See "Multiple
MECHANICALLY VENTILATED CRAWLSPACE SYSTEM:
A system designed to increase ventilation within a crawlspace, achieve higher
air pressure in the crawlspace relative to air pressure in the soil beneath the
crawlspace, or achieve lower air pressure in the crawlspace relative to air
pressure in the living spaces, by use of a fan.
MICROBIOLOGICALS: See "Biological
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.
MODEL CODE ORGANIZATIONS: Includes the
following agencies and the model building codes they promulgate:
- Building Officials and Code Administrators
International, Inc. (BOCA National Building Code/1993 and BOCA National
- International Conference of Building Officials
(Uniform Building Code/1991 and Uniform Mechanical Code/1991);
- Southern Building Code Congress,
International, Inc. (Standard Building Code/1991 and Standard Mechanical
- Council of American Building Officials (CABO
One- and Two-Family Dwelling Code/1992 and CABO Model Energy Code/1993).
CHEMICAL SENSITIVITY (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.
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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.
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ORGANIC COMPOUNDS: Chemicals that contain
carbon. Volatile organic compounds vaporize at room
temperature and pressure. They are found in many indoor sources, including many
common household products and building materials.
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."
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PELs: Permissible Exposure Limits
(standards set by the Occupational, Safety and Health Administration - OSHA).
PICOCURIE (pCi): A unit for measuring
radioactivity, often expressed as picoCuries per liter (pCi/L) of air.
PLENUM: Air compartment connected to a
duct or ducts.
PM: Preventive Maintenance.
POLLUTANT PATHWAYS: Avenues for
distribution of pollutants in a building. HVAC systems are the primary pathways
in most buildings; however all building components interact to affect how air
movement distributes pollutants. Also - a term used in the IAQ
Tools for Schools: IAQ Coordinator's Guide.
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.
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, 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.
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.
PSYCHOSOCIAL FACTORS: Psychological,
organizational, and personal stressors that could produce symptoms similar to
those caused by poor indoor air quality.
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RADIANT HEAT TRANSFER: Radiant heat
transfer occurs when there is a large difference between the temperatures of two
surfaces that are exposed to each other, but are not touching.
RADON (Rn) AND
RADON DECAY PRODUCTS: Radon is a radioactive gas formed in the decay of
uranium. The radon decay products (also called radon daughters or progeny) can
be breathed into the lung where they continue to release radiation as they
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.
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.
RELs: Recommended Exposure Limits
(recommendations made by the National Institute for Occupational Safety and
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SANITIZER: One of three groups of antimicrobials registered by EPA for public health uses. EPA considers an
anti-microbial 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 microorganism over the parallel control.
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 velocity that results in
mixing throughout the space.
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
SOIL GAS: The gas present in soil which
may contain radon.
SOIL-GAS-RETARDER: A continuous membrane
or other comparable material used to retard the flow of soil gases into a
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.
STACK EFFECT: The overall upward movement
of air inside a building that results from heated air rising and escaping
through openings in the building super structure, thus causing an indoor
pressure level lower than that in the soil gas beneath or surrounding the
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 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."
SUB-SLAB DEPRESSURIZATION SYSTEM (ACTIVE):
A system designed to achieve lower sub-slab air pressure relative to
indoor air pressure by use of a fan-powered vent drawing air from beneath the
SUB-SLAB DEPRESSURIZATION SYSTEM (PASSIVE):
A system designed to achieve lower sub-slab air pressure relative to indoor air
pressure by use of a vent pipe routed through the conditioned space of a
building and connecting the sub-slab area with outdoor air, thereby relying
solely on the convective flow of air upward in the vent to draw air from beneath
SUB-MEMBRANE DEPRESSURIZATION SYSTEM:
A system designed to achieve lower sub-membrane air pressure relative to
crawlspace air pressure by use of a fan-powered vent drawing air from under the
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TRACER GASES: Compounds, such as sulfur
hexafluoride, which are used to identify suspected pollutant pathways and to
quantify ventilation rates. Trace gases may be detected qualitatively by their
odor or quantitatively by air monitoring equipment.
TLVs - Threshold Limit Values (guidelines
recommended by the American Conference of Governmental Industrial Hygienists).
TVOCs. Total volatile organic compounds.
See "Volatile Organic Compounds (VOCs)"
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UNIT VENTILATOR: A fan-coil unit package
device for applications in which the use of outdoor- and return-air mixing is
intended to satisfy tempering requirements and ventilation needs.
VARIABLE AIR VOLUME SYSTEM (VAV): Air
handling system that conditions the air to constant temperature and varies the
outside airflow to ensure thermal comfort.
VENTILATION AIR: Defined as the total air,
which is a combination of the air brought inside from outdoors and the air that
is being re-circulated 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."
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").
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. At present, not much is known about what
health effects occur at the levels of VOCs typically found in public and
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ZONE: The occupied space or group of
spaces within a building which has its heating or cooling controlled by a single
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