Sick House Glossary

These are brief descriptions of sick house and indoor air quality terms for general informational purposes only.

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

Acute - A condition involving relatively brief periods of time. For CO exposure, acute is defined as an exposure of up to 10-15 hrs or less, involving one major exposure.

Additive effect - A biological response to exposure to multiple chemicals which is equal to the sum of the effects of the individual agents.

Air infiltration - Air leakage into a building.
Air return - Air returned from conditioned or refrigerated space.

Allergen - A substance capable of causing an allergic reaction because of an individual's sensitivity to that substance.

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.

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.

Bacteria - Microorganisms that have no true nucleus, a single chromosome, and no mitochondria, capable of causing adverse health effects.

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.

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.

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

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.

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.

CO - Carbon monoxide. CO2 - Carbon dioxide.

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.

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.)

CPSC - Consumer Product Safety Commission.

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 - 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.

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.

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

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

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.

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.

Exposure - The initial contact of the body with a substance.

Fungi - Any of a group of parasitic lower plants, including molds and mildews, that lack chlorophyll. (see mold)

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

Hazardous air pollutants - 189 chemicals considered by the EPA to be hazardous to human health.

HEPA - High efficiency particulate air (arrestance) filtration technology.

Humidifier fever - A respiratory illness that may be caused by exposure to toxins from microorganisms found in wet or moist areas of humidifiers and air conditioners. Also called air conditioner fever or ventilation fever.

HVAC - Acronym for heating, ventilating, and air conditioning system.

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.

IAQ - Acronym for Indoor Air Quality.

Immunocompromised - When the body's natural defenses to infection are below normal.

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

Legionnaires' disease - An illness which is sometimes fatal and whose symptoms mimic pneumonia. It is caused by a bacterium (Legionnella pneumophila) and primarily attacks immunocompromised individuals.

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

Microbiologicals - See Biological Contaminants.

Mold - Growth produced by any of a large group of fungi which has a cottony or furry appearance. (see fungi)

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.

Mycotoxins - Metabolites produced by fungi that have a broad spectrum of toxic effects ranging from mild acute toxicity to potent carcinogenicity. Refer to Toxic Mold for more information.

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.

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.

Particles - Solids or liquids light enough to be suspended in air.

Pathogens - Disease-producing microorganisms or materials.

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.

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

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

Pulmonary toxicants - Substances that affect the respiratory tract.

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

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.

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.

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.

Standards - Usually, mandatory guidance which is founded on statutory authority and involves an enforcement program; however, sometimes used to refer to nonregulatory guidance (e.g., ASHRAE ventilation standards).

Static pressure - Condition that exists when an equal amount of air is supplied to and exhausted from a space. At static pressure, equilibrium has been reached.

Sterilizer - One of three groups of antimicrobials registered for public health uses. EPA considers an antimicrobial to be a sterilizer when it destroys or eliminates all forms of bacteria, fungi, viruses, and their spores. Because spores are considered the most difficult form of a microorganism to destroy, EPA considers the term sporicide to be synonymous with sterilizer.

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

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.

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.

Vapors - Vapors represent the gaseous phase of a substance that is normally liquid or solid at room temperature and atmospheric pressure.

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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