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Glossary

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.

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.

Acute effects

Those that occur immediately on exposure.

ADA

Americans with Disabilities Act of 1990.

Additive effect

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

Agnosia

Inability to perceive objects through otherwise normally functioning sensory channels.

AHERA

Asbestos Hazard Emergency Response Act.

AHU

Air handling unit refers to ventilation equipment in HVAC systems.

Air Cleaning

An IAQ control strategy to remove various airborne particles and/or gases before the air enters the occupied space. The three types of air cleaning most commonly used are particulate filtration, electrostatic precipitation, and gas absorption.

Air Exchange Rate

Used in two ways. First, the number of times that the outdoor air replaces the volume of air in a building per unit time, typically expressed in air changes per hour; second, the number of times that the ventilation system replaces the air within a room or area within the building.

Air infiltration

Air leakage into a building.

Akinesis

Inability to initiate changes in activity and to perform ordinary volitional movements rapidly and easily. It is the most disabling feature of Parkinson's disease.

Allergen

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

Alveolus

(plural = alveoli) A small microscopic sac that is the functional unit of the lung, the location at the far end of the respiratory tract where gas exchange occurs.

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.