Glossary of Indoor Air Quality Terms

Terms not defined herein should have their ordinary meaning within the context of their use. Ordinary meaning is as defined in “Webster’s Ninth New Collegiate Dictionary.”

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Absorption – The physiological process by which toxicants pass body membranes and enter the bloodstream or other body components from the site of exposure.

ACGIH – American Conference of Governmental Industrial Hygienists.

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.

Amoebae – A unicellular organism which may either obtain energy by means of photosynthesis or by ingesting other organic material. The organism has no wall or coat outside its cell membrane; it moves and feeds by means of pseudopodia.

Amygdala (amygdaloid nucleus) – coordinates autonomic and endocrine responses in conjunction with emotional states; part of the limbic system.

Angina – A disease marked by brief, sudden attacks of chest pain precipitated by a deficient supply of oxygen to the heart muscles. (Also known as angina of the chest or angina pectoris.)

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.

Antidote – A remedy to counteract the effects of a poison.

Antimicrobial – Agent that kills microbial growth. See disinfectant, sanitizer, and sterilizer.

Aphasias – disturbances of language ability.

Apraxia – inability to perform complex acts requiring sequences of muscle contractions or a planned strategy.

Arrestance – The ability of a filter to remove injected standard dust from the test air. It is calculated as a % relationship on a weight basis.

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.

Asterixis – Quick arrhythmic movements that occur due to brief interruptions in background tonic muscular contractions.

ASTM – American Society for Testing and Materials.

Ataxia – abnormalities in the execution of voluntary movements.

Athetosis – Inability to sustain muscles of the fingers, toes, tongue or any other group of muscles in one position; maintained posture is interrupted by continuous slow, purposeless movements.

Atopy – A genetically controlled predisposition to production of specific antibodies. Approximately 10% of the population suffer from this problem. Specific diseases include allergic rhinitis (hayfever), asthma, and atopic dermatitis.

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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.

Balint’s Syndrome – due to bilateral damage to the parietal-occipital regions; causes problems with visually guided motor movements.

Basal Ganglia – made up of the caudate nucleus and putamen (known together as the corpus striatum) and the globus pallidus. Roles in regulating movement and cognition. Damage to it causes seizure disorders, multiple-sclerosis-type disorders, decrement in intellectual capacity, judgment, ability to concentrate, memory, speech capability.

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

Broca’s area – region of the frontal lobe on left, that makes spoken language possible.

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

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Calibration – The comparison of an instrument response to known values of a parameter being measured.

Cancer – A disease characterized by malignant, uncontrolled cell growth in body tissue.

Carcinogen – A substance capable of producing cancer in a living organism.

Caudate Nucleus – part of basal ganglia; damage causes forms of aphasia.

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.

Cellular toxicant – A chemical which acts as a poison by temperature to meet heating and cooling needs.

CENTRAL AIR HANDLING UNIT (Central AHU)- This is the same as an Air Handling Unit, but serves more than one area.

Cephalea (cephalgia) – headache, pain in the head.

Cerebellum – occupies most of the posterior cranial fossa; damage produces ataxia, slurring of speech.

Cerebral Cortex – expansive mass of brain tissue covering the older parts of the brain including cerebral hemispheres and formed of sulci, consisting of 4 parts (frontal, parietal, occipital, temporal); 6th division of the C.N.S.; involved in vision, hearing, learning, memory, association, etc.

Cerebral Hemispheres – made up of the basal ganglia, hippocampus and amygdala; overlaid by cerebral cortex; affects emotion, learning

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.

Cheyne Stokes – characterized by rhythmic waxing and waning of the depth of ventilation, with a regular pattern of apnea, hyperventilation, etc.

Chorea – widespread arrhythmic movements of a forcible, rapid, jerky, restless type; movements are irregular and variable, but continuous. They may be simple or quite elaborate, and affect any part of body. Can be caused by damage to caudate nucleus.

Chronic – A condition involving relatively long periods of time. For CO exposure, chronic is defined as an exposure of 10-15 hrs or more, and may involve one or cycles of exposure.

Chronic effects – Those occurring after repeated long-term exposure and are seen months or years after initiation of exposure.

CIAO – (Interagency) Committee on Indoor Air Quality.

Cilia – Short, specialized extensions of cells that appear hair-like, often arranged in rows, and present in large numbers. In the human respiratory system, cilia act to propel mucous slowly upwards, removing captured foreign particles.

Circulation – air moved through the furnace heat exchanger and then through the house to provide heating or cooling. This may not have any outside air

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.

Coil – Component of HVAC system that acts as a heat exchanger, either adding heat or taking heat away from the air stream.

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.

COMBINATION FOUNDATIONS – Buildings constructed with more than one foundation type; e.g., basement/crawlspace or basement/slab-on-grade.

Combustion – additional air brought into the house to allow furnaces, boilers, clothes dryers, ranges and domestic hotwater heaters to burn. If the appliance has “sealed” combustion this air will not affect the air within the house.

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 systems.

Condensation – The process of changing a vapor to a liquid by extracting heat from the vapor.

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.)

Conductivity – the ability of water to conduct electricity. Conductivity measurement is used for estimating the amount of total dissolved solids in water.

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

Convection – Movement of molecules (gases) from a region of higher air pressure to a region of lower air pressure. Airflow can also be induced by a temperature gradient (e.g., stack effect).

CPSC – Consumer Product Safety Commission.

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).

Cyclic patterns of symptoms – One or more symptoms which occur at regular intervals (e.g., every morning).

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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.

Deadleg – a length of pipe ending at a fitting through which water flows only when the fitting is opened.

Dentate Nuclei – one of three deep nuclei within the cerebellum.

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.

Developmental toxicant – A chemical that acts as a poison by means of causing adverse effects on the developing organism, including death, structural abnormality, altered growth, and functional deficiency.

Diagnosis – Investigation or analysis of the cause or nature of a condition, situation, or problem.

Diencephalon – 5th division of the C.N.S.

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.

Diposlide – a glass or plastic slide coated with culture media on which microorganisms can be grown and estimated. Legionella does not grow on these media.

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.

DOE – Department of Energy.

Dose – The amount of a pollutant absorbed by the body, usually expressed as an amount per unit of body weight.

Dose-response relationship – The effect of a substance on a body increases as the dose increases; theoretically, the body may respond differently at different dose levels of a given substance.

DPD Test Kit – a kit for measuring free, combined and total chlroine residuals using the reagent DPD (N, N-diethyl-p-phenylene diamine). Many test kits available from swimming pool suppliers measure only total chlorine not free chlorine and consequently should not be used. Free chlorine residuals in excess of 10 mg/L 10 ppm) are capable of bleaching the indicator colour, rendering the test invalid. Samples of water may have to be diluted with distilled water, or other water which does not interfere with the test, to bring the sample within the range of the kit. Allowance must be made for the sample dilution factor when determining the free chlorine residual in the original sample.

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.

Dust spot efficiency – A measure (expressed in percent) of the ability of a filter to remove atmospheric dust from air.

Dysarthria – difficulty speaking.

Dyscalculia – inability to carry out mathematical calculations.

Dyslexia – disorders with reading; congenital or acquired.

Dysphagia – difficulty swallowing.

Dyspnea – difficulty in breathing.

Dystonia – Abnormally increased muscular tone that causes fixed abnormal postures; sometimes shifting postures result from irregular, forceful twisting movements that affect the trunk and extremities.

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Echolalia – limited ability to speak unless spoken to; response usually a direct echo of examiner.

Endotoxins – Bacterial by-products excreted into the environment.

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.

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).

ETS – Acronym for Environmental Tobacco Smoke. ETS is made up of the smoke emanating from the burning end of a cigarette and smoke that is inhaled by the smoker, and consists of over 4,700 compounds, including both gases and particles.

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.

Extra-pyramidal Signs – May different phenomena which are due to primary deficits (negative symptom) or new de-inhibited actions that have appeared due to lesions associated with the basal ganglia.

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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.

FLOW HOOD – Device that easily measures airflow quantity, typically up to 2,500 cfm.

Free Chlorine Measurement – the measurement of hypochlorous acid (an efficient disinfectant) and hypochlorite ion ( a poor disinfectant) in water. The ratio of these two materials in water is pH dependent. The pH range specified (7.0 to 7.6) ensures that sufficient hypochlorous acid is present to facilitate effective disinfection.

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.

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Gas Sorption – Devices used to reduce levels of airborne gaseous compounds by passing the air through materials to 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 other factors.

Gases – Individual atoms or molecules that spread evenly throughout a volume of air, and cannot be collected by ordinary particulate filters.

Gawz, The laws of – through any boundary (be it the house exterior wall, laundry, or the bathroom) whatever air gawz-outta that boundary must be replaced by air that gawz-inta the boundary by some other path. Whenever air gawz-outta the exterior wall it must ultimately be replaced somewhere by air that gaze-inta the house. Regardless of the architect or engineer’s arrow on a drawing, air gawz from higher pressure to lower pressure. Pressure changes are felt at the speed of sound. When you hear the kitchen exhaust fan, the pressure drop is also felt. There is only a short, less then ten second, delay, because of inertia, to accelerate air to full flow for any given pressure change related to the law of gawz.

Glabella Sign – coming soon

Globus Pallidus – part of the basal ganglia. Damage can result in flexion dystonia, impaired postural reflexes.

Goblet cell – Specialized cell found in the human respiratory system that serves to secrete mucus.

Guidance – Non-regulatory recommendations on how to achieve specific objectives.

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Habit Spasms – Seemingly voluntary movements but which individuals feel compelled to do to relieve tension (eg. sniffing, clearing of throat, pulling on collar).

Hazardous Air Pollutants – 189 chemicals considered by the EPA to be hazardous to human health.

Hemiballismus – Hyperkinetic movement disorder characterized by violent flinging motions in the arm contralateral to a lesion in or near the subthalamic nucleus. May be due to damage in basal ganglia.

Hemiplegia – Neural motor condition affecting one side of the body only. Paraplegia affects both sides.

HEPA – High efficiency particulate arrestance (filters).

Hippocampus – part of the limbic system; involved in memory storage; damage produces effects on short- to long-term memory, limbic system.

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.

Humidistat – A device, actuated by changes in humidity, used for the automatic control of relative humidity.

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.)

Hypersensitivity Diseases – Diseases characterized by allergic responses to animal antigens. The hypersensitivity diseases most clearly associated with indoor air 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 involve inflammation of the lungs. Most forms are thought to be caused by an allergic reaction triggered by repeated exposures to biological contaminants.

Hypokinesis – abnormally decreased mobility; abnormally decreased motor function or activity.

Hypothalamus – controls pituitary; regulates temperature, heart rate, blood pressure, food and water intake (autonomic functions, multi-glandular control); constitutes less than 1% of brain.

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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 implement the IAQ Action Packets.

IPM – Integrated pest management.

Immunocompromised – when the body’s natural defenses to infection are below normal.

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).

Irritants – Substances which inflame living tissue by chemical action at the site of contact, causing pain or swelling.

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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.

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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.

MCS – See Multiple Chemical Sensitivity.

Medulla Oblongata – 2nd division of the C.N.S.

Metabolism – In toxicology, refers to the biochemical changes that a chemical undergoes in the body.

mg/L (ppm) – milligrams per liter (parts per million). For practical purposes mg/L is assumed to be equal to ppm.

Microbial/Microbiological – Microscopic forms of life.

Microbiological Contamination – Infection or pollution by microscopic organisms.

Microbiologicals – See Biological Contaminants.

Micrographia – Characterized by very small, cramped handwriting.

Mid-brain – 4th division of the C.N.S.

Mists – Mist is a term loosely applied to any dispersion of liquid particles, many of which are large enough to be individually visible without visual aid.

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 Mechanical Code/1993);
* 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 Code/1991);
* Council of American Building Officials (CABO One- and Two-Family Dwelling Code/1992 and CABO Model Energy Code/1993).

Mold – Growth produced by any of a large group of fungi which has a cottony or furry appearance.

MSDS – Material Safety Data Sheet.

Mucus – Mucus droplets are secreted by specialized cells in the respiratory system, mucus currents, swept by cilia remove foreign particles from the trachea.

Multiple Chemical Sensitivity (MCS) – A term used by some people to refer to a condition in which a person is considered to be sensitive to a number of chemicals at very low concentrations. There are a number of views about the existence, potential causes, and possible remedial actions regarding this phenomenon.

Mutagens – Substances that induce a permanent change in the genetic material.

Mutism – unable to speak, inarticulate; inability or refusal to speak.

Mycotoxins – Metabolites produced by fungi that have a broad spectrum of toxic effects ranging from mild acute toxicity to potent carcinogenicity.

Myoclonus – Very brief, involuntary, random muscular contractions. Myoclus can occur spontaneously at rest, in response to sensory stimuli, or with voluntary movements.

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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.

Neurotoxins – Substances that prevent normal function of the central nervous system.

NIOSH – National Instititute for Occupational Safety and Health (U.S.A.)

NTIS – National Technical Information Service.

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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.”

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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.

pH – a term used to describe the hydrogen ion activity of a water system. A solution of pH 0 to 7 is acid, pH of 7 is neutral, pH 7 to 14 is alkaline.

PICOCURIE (pCi) – A unit for measuring radioactivity, often expressed as picocuries per liter (pCi/L) of air.

Plenum – An air compartment connected to a duct or ducts.

PM – Preventive Maintenance.

Poison – Any agent capable of producing a deleterious response in a biologic system, seriously injuring function, or producing death.

Policy – Recommendations defining responsibility and action.

Pollutant pathways – The routes followed by a pollutant from its emission (source) as it travels through a strucducts, air streams, etc.

Pons (+ cerebellum) – 3rd division of the C.N.S.

Pontiac Fever – A flu-like illness caused by Legionnella or a similar bacterium named after a 1968 outbreak in Pontiac, Michigan.

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.

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.

Psychosocial Factors – Psychological, organizational, and personal stressors that could produce symptoms similar to poor indoor air quality.

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.

Pulmonary Toxicants – Substances that affect the respiratory tract.

Purkinje Cells – a type of cell found in the cerebellar cortex.

Putamen – part of basal ganglia.

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QA/QC – Quality Assurance/Quality Control procedures are used to assess method performance, accuracy, and precision.

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Radiant Heat Transfer – Radiant heat transfer occurs when there is a large difference the temperatures of two No surfaces that are exposed to each other, but are not touching.

Radon – A radioactive gas formed by the decay of uranium.

Radon progeny – Radon particles that can be breathed into the lung, where they continue to release radiation as they further decay. Also known as radon decay products or radon daughters.

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)

Reproductive Toxicant – A chemical acting as a poison by means of causing adverse effects on the male or female reproductive system (e.g. fertility, pregnancy outcomes).

Respirable Particles – Those particles found in air that are capable of penetrating and being deposited in the deeper (non-ciliated) portion of the lung.

Rigidity – Muscle tone is high and there is continuous contraction and resistance to passive movement.

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.

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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.

Saprophytic – Depending at least in part on dead organic matter as a food source.

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.

Scientific Method – Systematic, step-by-step approach to problem solving.

Short-circuiting – Situation that occurs when the supply airflows to exhaust registers before entering the breathing zone. To avoid short-circuiting, the supply air must be delivered at a temperature and velocity that results in mixing throughout the space.

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)

Sorbent – A substance used for either absorption or adsorption.

Source emissions – Emissions generated at the origin of a pollutant.

Stack effect – Occurs when a house acts like a chimney. The warm air in the home is lighter than the cold air outside and rises in the building and escapes out the top. The cool air is drawn into the building as the warm air escapes.

Staged Approach – A systematic, step-wise approach to investigation providing built-in decision points at which progress is assessed, and the investigation is redirected as necessary.

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.

STEL – Short-term exposure limit

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.

Strategy – Identification of objectives, measures of success, authority, overall resource commitment, coordination efforts, and level and timing of activities.

Substantia nigra – an area of the midbrain. Lesions can result in akinesia. Due to tremor at rest of Parkinson’s disease.

Subthalamic nuclei – an area within the basal ganglia.

Surfactant – a soluble surface acting agent that reduces surface tension between particulate matter and water.

Syncope – faint; loss of consciousness.

Synergistic Effect – A biological response to exposure to multiple chemicals which is greater then the sum of the effects of the individual agents.

Systemic Toxicants – Substances that affect entire organ systems, often operating far from the original site of entry.

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Tachycardia – increase in heart rate.

Tachypnea – increase in breathing rate.

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.

Thalamus – part of cerebral hemispheres; process information reaching the cerebral cortex from rest of C.N.S.

Thermal Bridge – A heat-conductive element in a building assembly that extends from the warm to the cold side and provides less heat-flow resistance than the adjacent construction.

Thermal Discomfort – The sensation of being too cold or too warm

Threshold – The lowest dose of a chemical at which a specific measurable effect is observed. Below this dose, the effect is not observed.

Tics – Characterized by stereotyped, purposeless, and irregularly repetitive movements. Gilles de la Tourette syndrome is the most common and severe form of multiple tic disorder.

TLV – Threshold limit value

TLVs – Threshold Limit Values are the recommended concentrations of airborne contaminants to which workers may be exposed according to the ACGIH.

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.

Total dissolved solids – the total weight of dissolved substances in water, including those which are capable of conducting electricity and those which are not.

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.

Toxicant – A poison.

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.

Trachea – A tube which conducts air, also known as the windpipe in humans; the first main branch leading down from the throat towards the lungs.

Tremor – Rhythmic oscillations of a part of the body around a fixed point; usually involve the distal parts of limbs, the head, tongue or jaw.

TSCA – Toxic Substances Control Act.

Tuberculosis – An infection associated with crowding and inadequate ventilation; characterized by the formation of tubercles, wasting away of tissue, etc., often in the lungs.

Turbidity – a cloudy appearance in water that is caused by a suspension of colloidal or particulate matter.

TVOCs – Total volatile organic compounds.

TWA – Time-weighted average. The average exposure an individual would experience over the period of an entire shift (usually 8 hours), measured at the breathing zone.

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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.

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WHO – Acronym for the World Health Organization.

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Environmental Protection Agency’s (EPA) Website,
Orientation to Indoor Air Quality, Student Manual Volume 1. USEPA, 1992.
Orientation to Indoor Air Quality, Student Manual Volume 3. USEPA, 1992
Wayne State University, School of Medicine, Carbon Monoxide HQ. February 1998.