Z94.13 - Occupational Health & Safety

The terms and their definitions in this standard have primarily resulted from the merging of Z94.15 - Safety and Z94.16 - Occupational Health and Medicine.  The resulting compilation has resulted in the elimination of considerable duplication between Z94.15 and Z94.16.  In addition, approximately 1/3 of the definitions have been revised/updated and a number of new terms have been added to the standard based on the recommendations of subcommittee members. A current bibliography can be found at the end of this standard, with citations limited to 1980 or later editions.

Recognition is given to the following subcommittee members who contributed their expertise in recommending revisions and additions to the terms in this standard.


John Talty, MS, PE, DEE
Office of Extramural Coordination & Special Projects
National and Institute for Occupational Safety And Health


Robin Baker, MPH
Labor Occupational Health Program
University of California, Berkeley
Lawrence Gingerich, MS, CIH, CSP
Protective Environmental, Inc.

William Milroy, MD, PhD
Plant Medical Director
Capterpillar, Inc.

Timothy Pizatella, MS
Division of Safety Research
National Institute for Occupational Safety and Health
Shan Tsai, PhD, FACE
Shell Oil Co.

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A-SCALE. A filtering system that has characteristics which roughly match the response characteristic of the human ear at low sound levels (below 55 dB SPL, but frequently used to gauge levels to 85 dB). A-scale measurements are often referred to as dB(A).

ABATE.   To eliminate a hazard to comply with a regulatory standard that is being violated, e.g., to correct deficiencies identified during an inspection conducted under the authority of the Occupational Safety and Health Act.

ABNORMAL USE. Using tools and equipment for a purpose other than that for which they were intended to be used, and one which may not reasonably have been foreseen.


ABRASION. An area of body surface denuded of skin or mucous membrane due to an abnormal or unusual mechanical process. A scraping away of a portion of the skin surface epithelium.

ABRIDGEMENT OF DAMAGES. The right of the court to reduce damages in certain cases.

ABSOLUTE RISK. The probability that a person with stated characteristics will develop a given illness or injury.

ABSORPTION. Penetration of a chemical substance, a pathogen, or radiant energy through the skin or mucous membrane.

ACCELERATION ILLUSIONS. Incorrect perceptions of apparent motion resulting from acceleration-induced stimulation of the semicircular canals. This can be a significant cause of disorientation in aircraft pilots. Three specifically described illusions of frequent occurrence are:  ciriolis - A change of head position during a turning maneuver resulting in illusory motion of the aircraft.  oculogyral - A sensation of spinning in the opposite direction following cessation of a spinning or rolling maneuver.  oculogravic - A perceived tilt in the visual vertical during linear acceleration.

ACCELERATION SYNDROME (G-FORCE SYNDROME). Alterations in physiologic function and/or perceptual-motor performance resulting from the forces imposed on the body by changes in velocity of direction of movement. The most significant of the symptoms are related to the circulatory status of the central nervous system and progress from loss of peripheral vision through blackout to unconsciousness during increases in acceleration.

ACCIDENT.  That occurrence in a sequence of events that may produce unintended injury, illness, death, and/or property damage.  (Note: The term often implies that the event was not preventable.  From a health perspective, use of this term is discouraged since occupational injuries and illnesses should generally be considered preventable.)

ACCIDENT AND SICKNESS BENEFITS (NON-OCCUPATIONAL). Periodic payments to workers who are absent from work due to off-the- job disabilities through accident or sickness.

ACCIDENT CAUSE (CAUSAL FACTORS). One or more factors associated with an accident or a potential accident. Causal factors may be identified as time sequenced events and/or may be categorized as being related to human and/or environmental (e.g., equipment, machinery, atmospheric contaminant, temperature, etc.) influences and their interactions.

ACCIDENT COSTS. Monetary losses associated with an accident.

ACCIDENT EXPERIENCE. One or more indices describing accident performance according to various units of measurement (e.g., disabling injury frequency rate, number of lost-time accidents, disabling injury severity rate, number of first-aid cases, or dollar loss). A summary statement describing accident performance.

ACCIDENT HAZARD. A situation present in an environment or connected with a job procedure or process which has the potential for producing an accident.

ACCIDENT LOCATION. The exact position of the key event that produced the accident.

ACCIDENT POTENTIAL. A behavior(s) or condition(s) having a probability of producing an accident.

ACCIDENT PREVENTION. The application of countermeasures designed to reduce accidents or accident potential within system or organization. Programs directed toward accident avoidance. The reduction or elimination of behaviors and conditions having an accident potential.

ACCIDENT PROBABILITY. The likelihood of a worker, operation, or item of equipment becoming involved in an accident. The probability of a set of unsafe conditions and/or unsafe acts producing an accident.

ACCIDENT PRONENESS. A discredited theory of accident causation.  Originally used to attribute the cause of accidents to personality traits of individuals or groups of workers.

ACCIDENT RATE. Accident experience in relation to a base unit of measure (e.g., number of disabling injuries per 1,000,000 employee-hours exposure, number of accidents per 1,000,000 miles traveled, total number of accidents per 100,000 employee-days worked, number of accidents per 100 employees, etc.).

ACCIDENT RECORDS. Reports and other recorded information concerning employee accident experience.

ACCIDENT REPORTING. Collecting information for, and/or preparing and submitting to a designated individual or agency, an official report of an accident.

ACCIDENT STATISTICS. Descriptive or inferential data which provide information about accident occurrences.


ACCIDENT TYPE. A description of the occurrences directly related to the source of injury classification and explaining how that source produced the injury.  Accident type- answers the question:   How did the injured person come in contact with the object, substance, or exposure named as the source of injury, or during what personal movement did the bodily motion occur?

ACCIDENT-FREE. A record of no accidents, sometimes of specified types, relating to an operation, activity, or worker performance during a specified time period.

ACCLIMATIZATION. The state of successful physiologic adaptation of an individual to new climatic conditions.

ACCURACY (VALIDITY). The closeness with which a measurement approaches the true or actual value.

ACOUSTIC TRAUMA. Hearing loss caused by sudden loud noise in one ear, or by sudden blow to the head.  In most cases, hearing loss is temporary, although there may be some permanent loss.

ACQUIRED IMMUNE DEFICIENCY SYNDROME (AIDS).  An acquired defect in immune system function that reduces the affected person's resistance to certain types of infections and cancers. The disease is caused by infection with the human immunodeficiency virus (HIV).

ACT OF GOD. An accident causal factor generally interpreted as being beyond human control (e.g., lightning, flood, tornado, earthquake, etc.). Although the natural phenomenon itself may be beyond control, its effect can be controlled in many instances. Thus, the act of God classification should not be accepted as an excuse for not taking proper precautions or properly designing structures to reduce the severity of a so- called act of God- occurrence.


ACTIVITY SAMPLING. A measurement technique for evaluating potential accident-producing behavior. It involves the observation of worker and organizational behavior at random intervals and the instantaneous classification of these behaviors according to whether they are safe of unsafe.

ACTUAL EXPOSURE HOURS. Employee-hours of exposure taken from payroll or time clock records, wherever possible, and including only actual straight time worked (in hours) and actual overtime hours worked.

ACUITY. The sharpness of a sense. Pertaining to the sensitivity of hearing, vision, smell, or touch.

ACUTE EXPOSURE. Severe, usually critical, often dangerous exposure in which relatively rapid changes are occurring. An acute exposure normally runs a comparatively short course and its effects can be easier to reverse in contrast with a chronic exposure.  Exceptions include exposure to electrical energy and radiation.

ACUTE MOUNTAIN SICKNESS. A disorder occurring in individuals exposed to high altitudes (about 10,000 ft.) for relatively long periods (24 hrs. or more). It presents as malaise,  headache, and vomiting attributed to cerebral and pulmonary edema. It is probably related to both hypoxia and decreased atmospheric pressure.  It may be prevented by proper acclimatization. 

ACUTE RADIATION SYNDROME. The organic illness which follows exposure to relatively large acute doses of ionizing radiation.  It presents as one of three separately identified dose dependent syndromes:  central nervous system syndrome - Follows doses of 2000 rem [20 sievert (Sv)] or above producing relatively prompt shock and coma, uniformly fatal within hours to a day.  gastrointestinal syndrome - Follows doses of 500 to 2000 rem (5-20 Sv) producing nausea, vomiting, and diarrhea within hours to days and death usually occurring within a week.  hematopoietic syndrome - Follows doses of 100 to 500 rem (1-5 Sv) producing early nausea and vomiting followed by a lag period of several weeks after which infection and hemorrhage occur due to hematopoietic suppression.  At doses of 400 to 500 rem (4-5 Sv) death will occur in about 50% of the cases within 30 days. With adequate therapy the majority of affected individuals in this category can recover. 

ADJUSTER. An individual who determines the amount of loss suffered in an insurance claim.

ADSORPTION. The adhesion of molecules of a gas, liquid, or dissolved material to a surface.

AEROSOLS. Liquid droplets or solid particles dispersed in air, that are of fine enough particle size to remain so dispersed for a period of time. 

AGE-ADJUSTED DEATH RATE (AGE-STANDARDIZED DEATH RATE). The mortality rate of a population calculated for comparative purposes in such a way that allowance is made for the age distribution of the population. When mortality rates for two or more populations are adjusted in the same manner, they may be compared to each other as though the populations had the same age distributions. 

AGE-SPECIFIC DEATH RATE. The number of deaths occurring in a defined age group, per unit population in that age group, over a stated period of time. 

AGENCY (AGENT). The principal object, substance, or premises, such as tool, machine, or equipment, involved in an accident. The term is used either to designate the object most directly causing an accident, or the object inflicting injury or property damage.

AGENCY PART. The specific hazardous part of the agency that contributed to an accident occurrence or injury.

AIR CONTAMINANTS. Airborne particulates, gases, and vapors that are capable of causing illness or injury to workers upon ingestion, inhalation, or skin or mucous membrane contact.

AIR SAMPLING. Determining quantities and types of atmospheric contaminants by measuring and evaluating contaminants in a known volume of air.

AIRBORNE NOISE. A condition when sound waves are being carried by the atmosphere.

ALLEGED VIOLATION. A written violation issued by a regulatory agency.

ALLERGIC ALVEOLITIS. A granulomatous pneumonitis caused by inhalation of a specific allergen. Examples are: sequoias, farmer's lung, bagassosis, suberosis, and maple bark disease.

ALLERGY. A hypersensitive state acquired through exposure to a particular allergen, re-exposure bringing to light an altered capacity to react. 

AMBIENT. Environmental surrounding, background.

AMBIENT NOISE. Total noise present in an environment. Usually a composite of sounds from many sources, including characteristic and background noise.

AMERICAN COLLEGE OF OCCUPATIONAL AND ENVIRONMENTAL MEDICINE (ACOEM). An international medical specialty society whose members promote worker and environmental health through preventive services, clinical practice, research and teaching.

AMERICAN CONFERENCE OF GOVERNMENTAL INDUSTRIAL HYGIENISTS (ACGIH).  Professional society of persons employed by official governmental units responsible for full-time programs of industrial hygiene, educators, and others conducting research in industrial hygiene.  Functions mainly as a medium for the exchange of ideas and the promotion of standards and techniques in industrial health.

AMERICAN INDUSTRIAL HYGIENE ASSOCIATION (AIHA).  Professional society of industrial hygienists.  To promote the study and control of environmental factors affecting the health and well-being of workers. Accredits industrial hygiene laboratories.

AMERICAN SOCIETY OF SAFETY ENGINEERS (ASSE).  Professional society of safety engineers, safety directors and others concerned with accident prevention and safety programs.  Sponsors training, including safety education seminars.  Bestows awards; compiles statistics; maintains job placement service.

ANALYSIS, ACCIDENT. A separating or breaking up of an accident into its parts so as to determine their nature, proportion, function, or relationship. A statement of the results of this process. Commonly involves the identification and evaluation of the unsafe conditions and unsafe acts that are associated with an accident. The dissection of an accident and its results to determine the basic elements and the resultant or potential damage to persons and/or things.


ANECHOIC ROOM. A room in which all of the sound emanating from a source is essentially absorbed at the walls. Hence,  there are no reflections and the spatial sound radiation pattern of a source may be determined.  An anechoic room may be described as  echoless- or acoustically  dead.- The term may also refer to an electromagnetically echoless room.

ANODIZE. To coat a metal electrolytically with a protective film.

ANTAGONISM. The interaction of two or more physiologically active agents producing an effect which is less than the effect produced using equivalent doses of each agent presented individually.

ANTHRACOSILICOSIS. Pneumoconiosis caused by breathing air containing dust that has free silica as one of its components and that is generated in the various processes in mining and preparing anthracite (hard) coal and to a lesser degree bituminous coal. 

APPARENT VIOLATION. An item observed by the compliance officer and mentioned in the closing conference as a violation of federal OSHA standards.

APPROVAL AGENCY. An agency designated or authorized to sanction, consent to, confirm, certify, or accept as good or satisfactory for a particular purpose or use, a method, procedure, practice, tool, or item of equipment or machinery.

APPROVED (METHOD, EQUIPMENT, ETC.). A method, equipment, procedure, practice, tool, etc., which is sanctioned, consented to, confirmed, or accepted as good or satisfactory for a particular purpose or use by a person or organization authorized to make such a judgment.

ARSON. The burning of buildings and/or property with malicious or criminal design, generally utilizing highly flammable materials or explosives to spread the fire quickly, or deliberately placed obstructions to impede fire fighting. This action may be by the owner and/or others and is by law a crime subject to federal jurisdiction.

ARTIFICIAL RADIATION. Man made radioactivity produced by particle bombardment or electromagnetic irradiation (e.g., x- rays) as opposed to natural radioactivity.

ASBESTOS. Naturally-occurring, fibrous minerals that include the serpentine mineral chrysotile and fine amphibole minerals but excludes fibrous forms of other minerals.  It is incombustible and is used as thermal insulation.  The inhalation of the fibers can cause asbestosis, lung cancer, and mesothelioma. 

ASBESTOSIS.  A form of lung disease (pneumoconiosis) caused by inhaling fibers of asbestos and marked by interstitial fibrosis of the lung varying in extent from minor involvement of the basal areas to extensive scarring.

ASPHYXIATION. Suffocation resulting from being deprived of oxygen. Simple asphyxiants act mechanically by excluding oxygen from the lungs when breathed in high concentrations (examples: nitrogen, hydrogen, carbon dioxide). Chemical asphyxiants act through chemical action preventing oxygen from reaching the tissue, or else prevent the tissue from using it even though the blood is well oxygenated (e.g., carbon monoxide, hydrogen cyanide, aniline).

ASSIGNABLE CAUSE. A cause factor designated as having a relationship to an accident. A causal factor or several causal factors assigned to an accident based on a predetermined causal classification system.

ASSIGNED RISK. Many states have  unsatisfied judgment- or financial responsibility laws- which make the purchase of insurance mandatory. Some motorists cannot buy insurance for some reason, such as poor accident experience. To make it possible for them to be insured, there are  assigned risk- plans in which such risks are insured. These risks are rotated among the subscribing companies in proportion to the amount of automobile liability insurance each writes in the state. All companies writing this class of insurance are required to participate in this activity. A comparable system operates in some states with respect to worker's compensation.



ASSUMPTION OF RISK. The legal theory that a person who is aware of a danger and its extent and knowingly exposes himself to it assumes all risks and cannot recover damages, even though he is injured through no fault of his own.

ASTHMA. A disease characterized by increased responsiveness of the trachea and bronchi to various stimuli, manifested by difficulty in breathing caused by generalized narrowing of the airways. 

ATMOSPHERE, EXPLOSIVE. Atmosphere containing a mixture of vapor gas or particulate matter which is within the explosive or flammable range.

ATTACK RATE. The number of new cases of a disease or an injury per unit population occurring over a defined period of time.

ATTENTION. Focusing on a task all of the personal abilities (both mental and physical) necessary for the safe accomplishment of that task. The human characteristic of giving sufficient heed or observing and perceiving with sufficient care to help prevent accidents. A readiness to respond to stimuli in a safe manner.

ATTENUATION. Reduction of intensity; to render less virulent or harmful; to reduce in strength.

ATTENUATION (SOUND). The reduction, expressed in decibels, of sound intensity to an observer due to either the distance from the source of noise or due to a barrier or acoustically treated material.

ATTRIBUTABLE RISK IN THE EXPOSED. The rate of disease or injury in those exposed to a given causal agent that can be attributed to the given causal agent. 

ATTRIBUTABLE RISK IN THE POPULATION. The rate of disease or  injury in the total population that can be attributed to a given causal agent. 

ATTRIBUTABLE RISK PERCENT IN THE EXPOSED. The percentage of the rate of disease or injury in those exposed to a given causal agent that can be attributed to the given causal agent.

ATTRIBUTABLE RISK PERCENT IN THE POPULATION. The percentage of the rate of disease or injury in the total population that can be attributed to a given causal agent. 

AUDIBLE RANGE. The frequency range over which normal ears hear. Approximately 20 Hz, through 20,000 Hz. Above the range of 20,000 Hz, the term ultrasonic is used. Below 20 Hz the term subsonic is used.

AUDIOGRAM. A record of hearing level measured at several different frequencies, usually 500 to 6,000 Hz. The audiogram may be presented graphically or numerically.  Hearing level is shown as a function of frequency. 

AUDIOLOGIST. A person trained in the specialized problems of hearing and deafness.

AUDIOMETER. A signal generator or instrument for measuring objectively the sensitivity of hearing in decibels referred to audiometric zero.

AVERAGE DAYS CHARGED PER DISABLING INJURY. This measure expresses the relationship between the total days charged to a disabling injury and the total number of disabling injuries as defined by the ANSI Z16 Standard. The average may be calculated by use of the following formula:  Average days charged per disabling injury = Total days charged /  Total number of disabling injuries.  The following alternate formula may also be used to compute this measure:  Average days charged per disabling injury = Standard Injury Severity Rate /  Standard Injury Frequency Rate.

AVULSIONS. A tearing away of a portion of the skin or other body structure.


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