Knowledgebase -
Glossary of Terms
HealthyAir strives to be your source
of knowledge, service, and industry information for all your
indoor air quality, heating and cooling needs. Please scroll
down to find the term and its definition,
in alphabetic order.
Absolute humidity
The amount of water vapor in a given volume of air.
Absorption
The process of one substance entering into the inner structure
of another.
ACGIH
The American Conference of Governmental Industrial Hygienists
is a community of professionals who work to advance worker health
and safety through education and the development and dissemination
of scientific and technical knowledge.
ACH
Air changes per hour. the amount of air in a building that
leaks out or is removed by a fan and is replaced by outdoor air.
Usually listed as a fraction of one air change per hour, such
as .35 ACH.
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 for radon
EPA recommends home owners take action to lower radon levels
indoors when concentrations are above 4 pci/l.
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.)
Activated charcoal
A highly absorbent form of carbon used to remove odors and toxic
substances from liquids or gases.
Acute exposure
A single exposure to a toxic substance that results in biological
harm or death; usually characterized as lasting no longer than
a day.
Acute toxicity
The ability of a substance to cause poisonous effects resulting
in severe biological harm or death soon after a single exposure
or dose. Any severe poisonous effect resulting from a short-term
exposure.
Acute
Health effects which show up a short length of time after exposure.
An acute exposure runs a relatively short course.
Aerosol
A gaseous medium containing suspended particles
Aflatoxin
A toxic compound produced by a mold fungus in agricultural crops
and in animal feeds that have not been carefully stored. It can
cause hepatitis and liver cancer.
AFUE
Annual Fuel Utilization Efficiency - A rating that reflects
the efficiency of a gas furnace in converting fuel to energy.
A rating of 90 means that approximately 90% of the fuel is utilized
to provide warmth to your home.
AHAM
Association of Home Appliances Manufacturers
AIHA
American Industrial Hygiene Association
Air cleaning
An IAQ control strategy to remove various airborne particulates
and/or gases from the air.
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.
Air Handling Unit (AHU)
For purposes of this website, this 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.
Air Leakage Rating
The air leakage rating is a measure of how much air leaks through
the crack between the window sash and frame.
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.
ALA
American Lung Association is the oldest voluntary health organization
in the United States. Founded in 1904 to fight tuberculosis,
ALA today fights lung disease in all its forms, with special
emphasis on asthma, tobacco control and ETS.
Aldehydes
Reactive organic compounds that contain hc=o group such as formaldehyde
and hexanal.
Algae
Simple rootless plants that grow in sunlit waters at the level
of how many nutrients are available
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.
Allergy
An abnormal response of a hypersensitive person to chemical
and physical stimuli; allergic manifestations of major importance
occur in about 10 percent of the population (adjective form:
allergic).
Ambient air
The outdoor air surrounding an object
American Public Health Association
See APHA
Animal dander
Tiny scales of animal skin.
Annual Fuel Utilization Efficiency (AFUE)
An indication of how well a furnace converts energy into usable
heat. The rating is expressed as a percentage of the annual output
of heat to the annual energy input to the furnace.
Antigen
A substance that when introduced into the body stimulates the
production of an antibody. Antigens include toxins, bacteria,
foreign blood cells, and the cells of transplanted organs.
Antimicrobial
Agent that kills microbial growth. see "disinfectant," "sanitizer," and "sterilizer."
APHA
The American Public Health Association consists of a group of
public health professionals concerned with a broad set of issues
affecting personal and environmental health.
Arrestance
The ability of a filter to remove injected standard dust from
the test air.
Asbestos
A naturally occurring mineral fiber that can cause cancer.
ASHRAE
American Society of Heating, Refrigerating, and Air-conditioning
Engineers is an international group which is organized for the
purpose of advancing the arts and sciences of heating, ventilation,
air conditioning and refrigeration.
Aspergillus
A mold that can be very toxic due to the carcinogens they produce
(Aflatoxins). Can be seen in several different colors. Especially
toxic to the liver, brain, kidneys, and heart.
Auxiliary heat
The total of all electric resistance heat in the system, regardless
of its intended use.
B
Backdrafting
A condition caused by negative pressure in the home in which
the exhaust from combustion equipment such as hot water heaters,
fireplaces, or furnaces, is sucked back down the flue and into
the house.
Back-up heat
Same as emergency heat.
Bacteria / bacterium
Microorganisms, mostly single-celled; their DNA is naked rather
than being enclosed in a nucleus.
Bioaerosol
An airborne organic contaminant that is either generated by
or is itself a living organism; examples of bioaerosols are fungi,
bacteria, viruses, protozoa, pollen, animal dander, insect emanations,
microbial endotoxins, and human skin.
Biocide
Any poison that kills a living organism.
Biohazard
A combination of the words biological and hazard; organisms
or products of organisms that present a risk to humans.
Biological contaminants
Agents derived from, or that are, living organisms (e.g., viruses,
bacteria, fungi, pollen, and mammal and bird antigens) that can
be inhaled and can cause illness.
Biologicals
Dust mites, mold spores, mildew, pollen, animal dander, bacteria,
viruses.
Blower Doors
Energy contractors use blower doors to see how much air leaks
through windows, doors, and other places in your house.
BRI
Building-related illness: this term is used when symptoms of
a disease from several occupants of a building can be directly
linked to specific airborne contaminants in that building.
British Thermal Unit (BTU)
One British thermal unit, or Btu, is roughly equivalent to burning
one kitchen match. That may not sound like much, but a typical
home consumes about 100 million Btus per year.
Building envelope
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.
C
Carbon dioxide
Carbon dioxide (co2) is a colorless, odorless, and tasteless
product of combustion. All combustion processes and human metabolic
processes are sources of CO2. Concentrations of CO2 from people
are always present in occupied spaces.
Carbon monoxide poisoning
A poisoned state in which carbon monoxide gas has been breathed
and soaked up by the blood. Carbon monoxide can limit the ability
of the blood to transport oxygen.
Carbon monoxide
An odorless, colorless gas that is a product of incomplete
combustion. co is a health hazard.
Carcinogen
A substance that can cause or contribute to cancer.
CDC
Centers for Disease Control and prevention, located in Atlanta,
Georgia, is an agency whose purpose is to promote health and
quality of life by preventing and controlling disease, injury,
and disability.
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
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.
Chemical allergy
Adverse reaction to a chemical resulting from previous sensitization
to that chemical or one structurally similar
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.
Co
Carbon monoxide.
Co2
Carbon dioxide.
Colony forming unit
See CFU
Colony
A single point of growth of mold or bacteria
Combustion
Burning or rapid oxidation accompanied by a release of energy
Combustion air
Air that is supplied to combustion appliances to be used in
the combustion of fuels and the process of venting combustion
gases. Inadequate combustion air can lead to dangerous problems.
Condensation
The transformation of the water vapor content of the air into
liquid water on cold surfaces.
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.)
Conditioned space
The part of the home that is meant to be heated and/or cooled.
Typically includes the living area; may or may not include
unfinished basements, crawlspaces, and attics.
Conidiophore
A hypha with specialized cells that produce conidia.
Conidium (pl. conidia)
An asexual spore that is released when mature.
Contaminant
Any physical, chemical, biological, or radioactive substance
that can adversely affect air, water or soil.
Cooling coil
An arrangement of pipe or tubing that transfers heat from
air to a refrigerant or brine.
Damper
A device used to vary airflow through an air duct. A damper
may be immovable, manually adjustable, or part of an automated
system.
Dampproofing
Sealing the foundation walls to help prevent outside moisture
from entering the basement.
Dehumidification
The condensation of water vapor from air by cooling below
the dewpoint or removal of water vapor from air by chemical
or physical methods
Dehumidifier
System which removes humidity (moisture) from the air. Humidity
levels in a home should be below 50% to control dust mites
and mold growth.
Disinfectants
One of three groups of anti-microbials registered by the EPA
for public heath uses. The EPA considers an anti-microbial
to be a disinfectant when it destroys or irreversibly inactivates
infectious or other undesirable organisms.
Duct
A passageway made of sheet metal or other suitable material,
not necessarily leaktight, used for conveying air or other
gas at low pressures.
Dust mite allergen
Allergenic proteins (antigens) derived from dust mites
Dust Mite
The most common allergen-producing organism found in homes.
They are smaller than the period symbol, about 1/4 mm. Life
cycle is 1 to 3 months and female can lay up to 100 eggs. A
typical used mattress can have 100,000 to 10 million.
Dust spot efficiency
A measure of the ability of a filter to remove atmospheric
dust from air (expressed in percent).
Dust
An air suspension (aerosol) of particles of any solid material,
usually with particle size less than 100 micrometers
Electric Resistance Heating
A type of heating system that generates heat by passing current
through a conductor, causing it to heat up. These systems usually
use baseboard heaters, often with individual controls.
Electro-Luminescent Night Lights
Electro-luminescent materials glow when a small electrical
charge is applied to them.
Electronic Ballasts
An electronic device that regulates the voltage of fluorescent
lamps. Compared to older magnetic ballasts, electronic ballasts
use less electricity and are not prone to the flickering and
humming effects.
Emergency heat
The portion of electric resistance heat that comes on when
the heat pump shuts down due to a failure or due to operation
of a safety switch. Emergency heat usually uses all of the
auxiliary heat.
Emphysema
Chronic pulmonary disease characterized by loss of lung function
after many alveolar walls have been destroyed, with resulting
enlargement of the air space.
Endotoxin
A toxin produced by certain bacteria and released upon destruction
of the bacterial cell.
Energy Efficiency Ratio (EER)
The ratio of the cooling capacity of the air conditioner,
in BTU per hour, to the total electrical input in watts under
test conditions specified by the Air-Conditioning and Refrigeration
Institute.
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
or passive smoking).
EPA
United States Environmental Protection Agency.
ETS
Environmental tobacco smoke. also referred
to as "secondhand
smoke".
Evaporation
Change of state from liquid to vapor
Exfiltration
Air leakage outward through cracks and other openings such
as ceilings, floors and walls of a space or building
Exhaust ventilation
Mechanical removal of air from a portion of a building (e.g.,
from a bathroom fan, kitchen range hood, clothes dryer, or
central exhaust fan).
Exposure
The initial contact of the body with a substance.
Exterior Sheathing
The first covering of boards or of waterproof material on
the outside wall of a frame house or timber roof. Taping the
joints in this layer of material will help prevent air inleakage.
F
FDA
The Food and Drug Administration is the U.S. agency responsible
for the regulation of biotechnology food products. the major
laws under which the agency has regulatory powers include the
food, drug and cosmetic act, and the public health standards.
Flashing
Material for allowing proper drainage around the joints and
angles of the roof and penetrations through the roof and walls.
Fluorescent Lamps
Fluorescent lamps produce light by passing electricity through
a gas, causing it to glow. The gas produces ultraviolet light;
a phosphor coating on the inside of the lamp absorbs the ultraviolet
light and produces visible light.
Footing
The supporting base for the foundation walls.
Formaldehyde
Formaldehyde is a colorless water-soluble gas. due to its
wide use, it is frequently considered separately from other
VOCs. materials containing formaldehyde include building materials,
furnishing, and some consumer products.
Fungal propagules
Spores or hyphal fragments capable of producing colonies
Fungi
Any of a group of parasitic lower plants that lack chlorophyll,
including molds and mildews.
Fungicide
Biocides used to control, prevent, or kill fungi
Fungus
A organism without chlorophyll that reproduces by spores and
lives by absorbing nutrients from organic matter.
G
Gases
Formaldehyde, combustion by-products, volatile organic compounds.
Germicide
An agent capable of killing germs
H
Heat Exchanger
A device used to transfer hear from a fluid (liquid or gas)
to another fluid, where the two fluids are physically separated
(usually by metal tubing). Household examples of heat exchangers
are heating radiators and the coils on
Heat pump
The part of the heating/cooling system that uses refrigeration
equipment.
Heat Transfer
The flow of heat from one substance to another, for instance,
the flow of heat from your water heating element to the water
that surrounds it.
Heating Seasonal Performance Factor (HSPF)
The total heating output of a heat pump in BTU during its
normal usage period for heating divided by the total electrical
energy input in watt-hours during the same period.
HEPA
High Efficiency Particulate Arrestance (filters).
High-Pressure Sodium Lighting
High-pressure sodium lamps are a form of high-intensity discharge
(HID) lamps, which use an electric arc to produce intense light.
Histoplasmosis
A disease caused by the inhalation of spores of the fungus
histoplasma capsulatum, most often asymptomatic but occasionally
producing acute pneumonia or an influenza like illness.
HUD
Department of Housing and Urban Development is the federal
department that administers federal programs dealing with better
housing and urban renewal; created in 1965.
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 fever.
Humidifier fever
("ventilation fever") - A respiratory
illness caused by exposure to toxins from microorganisms
found in wet or moist areas in
humidifiers and air-conditioners.
Humidifier
A device to add moisture to the air
Humidity
Water vapor in the air
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
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.
Hypersensitivity
The immune system's exaggerated response to an allergen
Hyphae
Single threads of a fungal body, also used for certain bacteria
(actinomycetes)
I
IAQ
Indoor Air Quality.
Incandescent Light Bulbs
Incandescent light bulbs produce light by passing electricity
through a thin filament, which becomes hot and glows brightly.
Incandescent light bulbs are less energy-efficient than fluorescent
lamps, because much of th
Indoor air pollutant
Particles, dust, fibers, mists, bioaerosols, and gases or
vapors which can cause a variety of health effects and problems
in a building.
Infiltration
Air leakage inward through cracks and other openings such
as ceilings, floors and walls of a space or building
Insecticide
Any material or agent capable of killing insects
Internal Heating Elements
A feature in dishwashers that allows the machine to heat your
hot water to a higher temperature. Although this makes your
dishwasher use more energy, it also allows you to reduce your
hot water heater's temperature to
Irritant
Physical, biologic, or chemical stressors that induce acute
symptoms and inflammation of the tissue
J
No terms yet; if you have or would like a term or phrase on
this website defined, please let us know via our contact
page.
K
Kilowatt-Hour (kWh)
One kilowatt-hour (kWh) is equal to using 1000 watts of electricity
for one hour. This is equal to burning a 50-watt light bulb
for 20 hours, or roughly equivalent to cooking a pot of rice
for an hour.
L
Legionnaires' disease (or legionnaire's)
Illness produced by legionella pneumophila bacteria that can
affect lungs and other body systems
Local exhaust
Fans used to exhaust pollutants and moisture at or near their
source. bath fans, range hoods, and utility room fans are all
examples of local exhaust.
Low Emissivity (low-e) Coatings
Emissivity is a measure of how much heat is emitted from an
object by radiation. Heat is transferred to and from objects
through three processes: conduction, convection, and radiation.
M
Makeup air
Outdoor air supplied to replace exhaust air and exfiltration
Map of radon zones
EPA's map of radon zones assigns each of the 3141 counties
in the United States to one of three zones based on radon potential.
MCS
Multiple Chemical Sensitivity is an unexplained condition
where a person reports sensitivities and adverse reactions
to low levels of chemicals.
MDF
Medium density fiberboard is a type of particleboard. It is
made of wood particles glued together by synthetic resin, with
a medium density, as opposed to hardboard.
Mechanical ventilation
Ventilation from the operation of a fan, either exhausting
air from a house, supplying air, or both.
MERV
The Minimum Efficiency Reporting Value represents how effective
a filter is when removing particulates of a specific size.
The lowest rating values is 1, which includes disposable filters,
washable filters, and some electrostatic filters; the highest
value is 20. Only a true HEPA filter can be rated 20. HEPA
filters remove 99.97% of particulates .3 microns and larger.
Human hair is between 70 - 100 microns. View
MERV Chart
Metals
Lead paint, arsenic in treated lumber.
Methane
A colorless, flammable gas created by anaerobic decomposition
of organic compounds
Microbiologicals
See "biological contaminants".
Microorganism
A microscopic organism, especially a bacterium, fungus, or
a protist
Minerals
Asbestos, fiberglass insulation, airborne calcium particles
from humidifiers.
Mucous membranes
Lining of the hollow organs of the body, notably the nose,
mouth, stomach, intestines, bronchial tubes, and urinary tract
Multiple chemical sensitivity
A condition in which a person is considered to be sensitive
to a number of chemicals at very low concentrations.
MVOCs
Microbial volatile organic compounds are volatile chemicals
produced by the metabolism of fungi and bacteria.
Mycotoxin
A poisonous substance produced by a Fungus.
N
Natural ventilation
The movement of air into and out of a home through random
holes and cracks, and open windows and doors. the air movement
is caused by wind and by temperature differences (which drives
the stack effect).
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 f
Neurotoxic
Chemicals that cause central nervous system (CNS) problems
such as dizziness, headaches and ability to think clearly
NIH
The National Institutes of Health is a nonregulatory u.s.
federal agency that has oversight of research activities that
the agency funds.
NIOSH
National Institute for Occupational Safety and Health is part
of the centers for disease control and prevention (CDC) and
is the only federal institute responsible for conducting research
and making recommendations for the prevention of work related
injuries.
O
Occupational Health and Safety Administration
See OSHA
Off-gassing
The production of gases from the chemical deterioration of
a substance over time, and the release of gases from materials
into the air.
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.
OSHA
Occupational Safety and Health Administration is the agency
in the u.s. department of labor that enforces safety and health
regulations in private workplaces to ensure safe and healthy
working conditions.
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.
Ozone (o3)
A reactive form of oxygen that is a strong mucous membrane
and pulmonary irritant
P
Particulate matter
A suspension of fine solid or liquid particles in air, such
as dust, fog, fume, mist, smoke, or sprays. Particulate matter
suspended in air is commonly known as an aerosol.
Passive radon-reduction system
Short for "passive sub-slab depressurization system".
approach for reduction of radon levels which utilizes barriers
to radon
entry and stack effect reduction techniques to reduce the rate
of radon entry, plus th
Pathogen
Any microorganism capable of causing disease
Pci/l
Picocuries per liter (of air), unit for measuring radon concentrations.
the EPA action level for indoor radon is 4 pci/l.
PCM
Per cubic meter, for example, is the number of CFUS in a one-meter
cube of air.
PEL
Permissible exposure level is an exposure limit that is published
and enforced by OSHA as a legal standard.
Penicillium
Dense mold with a brush-like appearance. Tends to emerge at
sub-basement levels and rooms. It can grow in fairly dry conditions.
Perchloroethylene
A colorless, nonflammable organic solvent, used in dry-cleaning
solutions and as an industrial solvent
Pesticide
A chemical used to kill pests (as rodents or insects)
Picocurie
A unit for measuring radioactivity, often expressed as picocuries
per liter (pCi/L) of air.
Plenum
Air compartment connected to a series of ducts. for example,
a ceiling plenum is the space above the suspended ceiling and
below the floor above that is used as part of the air distribution
system.
Pneumonia
A swelling of the lungs, commonly caused by breathed-in bacteria
(diplococcus pneumoniae). Parts of the lungs become plugged
with a fiber-like fluid. Pneumonia may also be caused by rickettsiae,
viruses, and fungi.
Pollutant pathways
Avenues for distribution of pollutants in a buildings. HVAC
systems are the primary pathway in most buildings; however,
all building components interact to affect how air movement
distributes pollutants.
Pollutant
An airborne contaminant associated with illness
Pontiac fever
A milder illness of legionnaires' disease. Persons with pontiac
fever experience fever and muscle aches and do not have pneumonia.
They generally recover in 2 to 5 days without treatment.
Positive pressure
Condition that exists when more air is supplied to a space
than is exhausted from the space, so the air pressure within
that space is more than that in surrounding areas.
PPB
Parts per billion.
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.
Preventive maintenance
Regular and systematic inspection, cleaning, and replacement
of worn parts, materials, and systems. Preventive maintenance
helps to prevent parts, materials, and systems failure.
Q
No terms yet; if you have or would like a term or phrase on
this website defined, please let us know via our contact
page.
R
Radiation
Radon, electromagnetic fields, radioactive material in some
smoke detectors and compact fluorescent lights.
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 fur
Radon
A naturally occurring odorless, colorless, and tasteless radioactive
gas. It comes from the decay of radium.
Relative humidity
Relative humidity is the ratio of the amount of water in the
air at a given temperature to the maximum amount it could hold
at that temperature; expressed as a percentage.
Respirable particles
Particles that penetrate into and are deposited in the lungs.
Particles greater than 10 microns are not respirable.
RH
See Relative Humidity
Rhinitis
Inflammation of nasal mucous membranes; "runny
nose"
S
SBS
Sick building syndrome refers to when many occupants in a
building or in the same part of a building experience immediate
health problems that seem to be due to the building, but no
specific illness or cause can be identified.
Seasonal Energy Efficiency Ratio (SEER)
The total cooling output of a central air conditioner in British
thermal units during its normal usage period for cooling divided
by the total electrical energy input in watt-hours during the
same period
SEER
Seasonal Energy Efficiency Ratio. The total cooling output
of a central air conditioner in British thermal units during
its normal usage period for cooling divided by the total electrical
energy input in watt-hours during the same period.
Sensitization
An allergic condition that usually affects the skin or lungs.
Once exposure to a substance has caused a reaction, the individual
may be sensitized to it, and further exposure may elicit an
adverse reaction even at low levels.
Sick building syndrome
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.
Sick building
A building whose occupants complain of health and comfort
problems that can be related to working or being in a building
Sinusitis
A swelling of one or more nasal sinuses. It may be a complication
of an upper respiratory infection, dental infection, allergy,
a change in atmosphere, as in air travel or underwater swimming,
or a defect of the nose.
Solar Heat Gain Coefficient (SHGC)
The solar heat gain coefficient, also called a shading coefficient,
is a measure of how well a window absorbs or reflects heat
from the sun. The lower the coefficient, the better the window
is at blocking the heat.
Solvent
Substances that can dissolve other substances.
Water is the universal solvent, most people mean organic
solvents when they
refer to these chemicals./p>
Source control
Strategy for reducing airborne contaminants by removing or
reducing emitting materials or activities.
Spectrally Selective Coatings
A type of window glazing film that blocks the infrared portion
of sunlight while admitting the visible portion.
Spore
A small, usually single-celled reproductive body that is highly
resistant to dehydration and heat and is capable of growing
into a new organism, produced especially by certain bacteria,
fungi, algae, and nonflowering plants
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.
Sterilizer
One of three groups of anti-microbials registered by the EPA
for public heath uses. EPA considers an anti-microbial to be
a sterilizer when it destroys or eliminates all forms of bacteria,
fungi, viruses, and their spores.
Storm Windows
An extra pane of glass or plastic added to a window to reduce
air infiltration and boost the insulation value of a window.
Sub-slab depressurization
A system designed to achieve lower sub-slab air pressure relative
to indoor air pressure (used in radon control and mitigation).
may be a passive system (no fan) or an active system (with
fan).
Supplemental heat
The portion of electric resistance heat used to make up for
the heat pump's inability to heat the house during very cold
temperatures and during defrost.
Surface thermometers
As the name implies, surface thermometers have a temperature
probe that can be placed directly on a surface to see what
temperature it is.
T
TLV
Threshold limit value is the air concentration of chemical
substances to which healthy workers can be exposed for 8-hour
work days during a 40-hour work week without suffering an adverse
effect.
Ton
It can get a little confusing talking about the heating or
cooling capacity of a heat pump. A common sizing measurement
is the \
Toxicity
Inherent ability of a chemical to adversely affect living
organisms
Toxicology
Study of harmful effects of chemicals on living organisms
Toxin
A substance produced by a living organism that injures tissues
or alters the functions of another organism
Tuberculosis
An infectious disease of human beings and animals caused by
the tubercle bacillus and characterized by the formation of
nodules on the lungs and other tissues of the body, often developing
long after the initial infection.
TVOC
Total volatile organic compounds are the sum of all volatile
organics collected and analyzed by a defined analytical method.
U
UEL
Upper explosive limit is the highest concentration (expressed
in percent vapor or gas in the air by volume) of a substance
that will burn or explode when an ignition source is present.
Upper respiratory tract
Structures that conduct air into the lungs, including the
nasal cavity, mouth, pharynx, and larynx
UV Light
Ultra-Violet light
U-value
The U-value, also called the U-factor, is a measure of how
well heat flows through an object (thermal conductivity). It
is also referred to as the heat transfer coefficient or the
coefficient of heat transmission.
V
Vapor Barrier
Also called a vapor retarder, this is a material that retards
the movement of water vapor through a building element (such
as walls, floors, and ceilings) and prevents metals from corroding
and insulation and structural wood from
Vapor
Any gas below its critical temperature; barely visible or
cloudy diffused matter, such as mist, fumes, or smoke, suspended
in the air.
Ventilation rate
The rate at which indoor air enters and leaves a building.
Ventilation
The process of supplying and removing air by natural or mechanical
means to and from any space; such air may or may not be conditioned
VOCs
Volatile organic compounds: chemicals containing carbon are
called organic. Volatile means that they evaporate or get into
the air easily which make them easier to inhale.
Volatile Organic Compounds
Off-gassing from synthetic furnishings, building and cleaning
materials, and tobacco smoke can produce gaseous pollutants
which when inhaled can weaken lung and heart tissue.
W
Water activity (aw)
A measure of the amount of water held within materials
WHO
The World Health Organization is a United Nations Agency that
coordinates international health activities and helps governments
improve health services.
Whole-House Fan
A large fan used to ventilate your entire house. This is usually
located in the highest ceiling in the house, and vents to the
attic or the outside.
X
Xerotolerant
Able to grow under relatively dry conditions (damp rather
than wet)
Y
No terms yet; if you have or would like a term or phrase on
this website defined, please let us know via our contact
page.
Z
Zone
The occupied space or group of spaces within a building
which has its heating or cooling controlled by a single thermostat.
| 
