Safety Glossary

Select the first letter of the word from the list above to jump to appropriate section of the glossary. If the term you are looking for starts with a digit or symbol, choose the '#' link.


Absolute Pressure - The total pressure within a vessel, pipe, etc., not offset by external atmospheric pressure.

Absorb - To soak up. The incorporation of a liquid into a solid substance, as by capillary, osmotic, solvent, or chemical action.

Acrid - irritating and bitter (usually referring to smell).

Acidosis - condition of decreased alkalinity of the blood tissues. Symptoms may include sickly sweet breath, headache, nausea, vomiting, visual disturbances. Tissues and CNS functions are disturbed.

Action Level - The exposure level (concentration in air) at which OSHA regulations to protect employees take effect (29 CFR 1910.1001-1047); e.g., workplace air analysis, employee training, medical monitoring, and record keeping. Exposure at or above action level is termed occupational exposure. Exposure below this level can also be harmful. This level is generally half the PEL.

Acute effects - adverse effect on a human or animal body, with symptoms developing rapidly.

Acute Toxicity - adverse health effects resulting from brief exposure to a chemical.

ALARA - Acronym for "as low as reasonably achievable".

Allergen - Substance that causes an allergic reaction.

Allergy - condition in which an initial symptomless exposure to a specific allergen later gives rise to a sensitivity to further exposure.

Alopecia - loss of hair.

Analgesia - reduced sensitivity to pain.

Anesthesia - loss of sensation, including loss of touch, pain, vibration sense, and/or temperature sense.

Anorexia - loss of appetite.

Anosmia - loss of the sense of smell.

Anoxia - lack of oxygen in blood or tissues.

Antidote - remedy to counteract a poison's toxic effects.

Anuria - absence or defective excretion of urine.

Apnea - temporary stoppage of breathing.

Appearance - a material's physical state (solid, liquid, or gas), it's color, and the other visual attributes.

Argyria - local or generalized gray-blue colored impregnation of body tissue with silver.

Asbestosis - Chronic lung disease caused by inhaling airborne asbestos fibers.

Asphyxia - lack of oxygen or inability of cells to use oxygen; simple asphyxia is suffocation caused by a lack of oxygen in the inhaled air; chemical asphyxia poisons the blood's ability to carry oxygen or the cell's ability to use oxygen.

Asphyxiant - a vapor or gas that can cause unconsciousness or death by suffocation.

Asphyxiation - a condition that causes asphyxia or suffocation.

Asthma - medical disorder which causes attacks of wheezing, chest tightness, shortness of breath, and/or coughing due to spasmodic contraction of the air passage.

Ataxia - loss of muscular coordination of gait or movement.

Atrophy - reduction in size or function of tissue, organs, or the entire body caused by lack of use.

Autoignition Temperature - This tells you how hot a material must be before it will set itself on fire without a flame or spark.


BLEVE - (Boiling Liquid Expanding Vapor Explosion) Used when describing fires involving compressed gases in cylinders which rupture due to extreme pressures and proceed to burn rapidly.

BOD - (Biochemical Oxygen Demand) Amount of oxygen needed by bacteria to stabilize organic matter under aerobic conditions. Used to estimate degree of contamination in water supplies.

Body Burden - The total toxic material a person has ingested or inhaled from all sources over time and retained in the body. for example, lead can be ingested form drinking water channeled through lead-soldered pipes, lead glazes on dishes, or flakes from painted surfaces, as well as from many industrial operations.

Boiling point - the temperature at which a liquid's vapor pressure equals the surrounding atmospheric pressure so that the liquid rapidly vaporizes.

Bonding - A safety practice where two objects (tanks, cylinders, etc.) are interconnected with clamps and wire. This equalizes the electrical potential between the objects and helps prevent static sparks that can ignite flammable materials transferred between tanks.

Bronchitis - inflammatory condition of the airways resulting in production of phlegm(sputum).

Bulk density - mass per unit volume of a solid particulate material as it is normally packed, with voids between particulates containing air.

Burning Rate - The time it takes a specified sized sample of solid material (e.g. 1 in by 1 in) to burn a designated distance. The rate is given in units of distance/time.


C - (CEL)Ceiling Exposure Limit is not to be exceeded at any time for any purpose.

Carcinogen - A material that causes cancer in humans, or, because it causes cancer in animals, is considered capable of causing cancer in humans.

Cardiovascular (CVS) - system of the human body involving the heart and blood vessels.

CAS Number - an assigned number used to identify a chemical. CAS stands for Chemical Abstracts Service, an organization that indexes information published in chemical abstracts.

Catalyst - Substance that modifies (slows or more often quickens) a chemical reaction without being consumed in the reaction.

Cataract - loss of transparency in the eye's lens. A frequent consequence of exposure to laser or to 50 Rem of radiation to the eye.

Centipose - a metric unit of viscosity equal to 1/1000 poise.

Central Nervous System (CNS) - the brain and spinal cord.

Chelating Agent - a substance which can remove heavy metals from the blood.

Chloracne - severe form of skin acne caused by exposure to certain chlorinated chemical compounds.

Chronic Effects - an adverse effect on a human or animal with symptoms that develop slowly over a long time period and persist or that recur frequently.

Clastogenic - an agent that causes damage to genetic material.

CNS Depression - drowsiness, dizziness, and headache caused by a chemical acting on the brain; higher doses can cause unconsciousness, coma, or death.

Coefficient of water/oil distribution - (partition coefficient) the ratio of the solubility of a chemical in water to its solubility in oil.

Coma - extended loss of consciousness due to an injury, illness, or poison.

Combustible - Materials that will burn under most conditions and may ignite easily.

Combustible Liquids - Liquid with a flash point at or above 100ºF(38ºC) but below 200ºF (93.3ºC).

Conjunctivitis - irritation and inflammation of the lining of the eye and eyelids.

Convulsions - violent body spasms; fits or seizures.

Cornea - transparent structure of the eyeball's external layer.

Corrosive - A chemical that causes visible destruction of or irreversible alterations in living tissue by chemical action at the site of contact, or which causes a severe corrosion rate in steel or aluminum.

Corrosion rate - expressed in inches or millimeters of steel (or other defined material) per year, at a stated temperature.

Critical Temperature - a temperature above which a material cannot be liquefied by pressure.

Critical Pressure - The critical pressure is that pressure required to liquefy a gas at it's critical temperature.

Cyanosis - dark-blue to purplish coloration of the skin and the mucous membrane caused by oxygen depravation to the body (i.e. obstructed airway or chemically induced e.g. cyanide)


Density - Ratio of weight to volume of a material, usually in grams per cubic centimeter or pounds per gallon.

Dermatitis - skin rash; inflammation of the skin.

Diaphoresis - perspiration, especially profuse.

Dysplasia - abnormal growth or development of organs or cells

Dyspnea - sense of difficulty in breathing; shortness of breath.

Dysuria - difficult or painful urination.


Eczema - skin rash characterized by redness, itching, sometimes blistering; may become scaly or crusty.

Edema - swelling due to accumulation of fluid in tissues.

Embolism - obstruction of a blood vessel by a transported clot.

Embryo - organism in the early stages of development before birth. In humans, the developing child is considered an embryo from conception to the end of the second month of pregnancy.

Emetic -an agent which induces vomiting.

Emphysema - an irreversible lung condition in which the alveolar walls lose resiliency, resulting in excessively reduced lung capacity. Frequently associated with long term smoking.

Epipohora - excessive flow of tears.

Epistaxis - nosebleed.

Erythema - redness of the skin; usually due to increased blood flow.

Evaporation Rate - the rate at which a material vaporizes from the liquid or solid state when compared to a known material's vaporization rate. The known reference material is usually normal butyl acetate(N-BuAc).

Explosive or Flammable Limits - Lower (LEL) and upper (UEL) explosion limits are the minimum and maximum concentrations of a flammable gas or vapor (percent by volume in air) between which an explosion can occur if an ignition source is present.

Extinguishing Media - These are the materials which may be used to extinguish a fire.


Fibrosis - scarring in the lungs may affect oxygenation of blood.

Flammable or Explosive Limits - Lower (LEL) and upper (UEL) explosion limits are the minimum and maximum concentrations of a flammable gas or vapor (percent by volume in air) between which an explosion can occur if an ignition source is present.

Flash point - This is the lowest temperature at which a flammable liquid gives off enough vapor to form an ignitable mixture with air.

Formula Mass - the sum of atomic weights of the atoms in a molecule.

Freezing Point - the temperature at which a material changes from a liquid to a solid state upon cooling.

Fume Hood (Laboratory-type Hood) - an enclosed laboratory cabinet with moveable sash or fixed access port on the front, connected to a ventilating system which may incorporate air scrubbing or filtering facilities. It enables employees to manipulate materials in the hood using only their hands and arms.


Gangrene - death of tissue leading to it's rotting. A frequent complication of frostbite (as from liquid helium or liquid nitrogen)

Gastroenteritis - stomach and intestine inflammation.

Gastrointestinal tract (GI tract) - the stomach and intestine as a functional unit.

Gestation - development of the fetus in the womb from conception to birth.

Gingivitis - inflammation of the gums.


Hazardous Decomposition - a breaking down or separation of a substance into its constituent parts, elements, or into simpler compounds accompanied by the release of heat, gas, or hazardous materials.

Hematuria - blood in urine.

Hemolysis - destruction of red blood cells leading to release of hemoglobin.

Hepatic - pertaining to liver.

Hydrophilic - Materials having large molecules that tend to absorb and retain water, causing them to swell and frequently to gel.

Hygroscopic - Readily adsorbs available moisture in any form.

Hypergolic - Self igniting upon contact of its components without a spark or external aid.

Hyperemia - congestion of blood in a body part.

Hypocalcemia - calcium deficiency of the blood.

Hypoxia - insufficient oxygen reaching the tissues of the body.


Incompatibles - describes materials that could cause dangerous reactions and the release of energy from direct contact with one another.

Ingestion - swallowing

Inhalation - breathing

Interstitial Fibrosis - scarring of the lungs.

Iodism - abnormal condition resulting from prolonged exposure to iodine. Characterized by emaciation, skin eruptions, headache, excess salivation, runny nose, and sneezing.

Iridocyclitis-inflammation of both eye's iris and its ciliary body.

Irritant - Substance capable of causing a reversible or irreversible inflammatory effect on living tissue by chemical action at the site of contact as a function of concentration or duration of exposure.


Jaundice - yellowish discoloration of tissue, white of eyes, and bodily fluids with bile pigment caused by liver damage, gall bladder disease, or hemolysis.


Ketosis - condition marked by excessive production or by the accumulation of ketones bodies in the body.


Laboratory-type Hood (Fume Hood) - an enclosed laboratory cabinet with moveable sash or fixed access port on the front, connected to a ventilating system which may incorporate air scrubbing or filtering facilities. It enables employees to manipulate materials in the hood using only their hands and arms.

Lacrimator - material that upon exposure causes tears.

Latency period - time that elapses between exposure and first manifestations of disease or illness.

Lavage - rinse with water.

Lethargy - sense of fatigue, drowsiness, and laziness.

Leukemia - progressive, malignant disease of the blood-forming organs.

Lipid granuloma - mass of chronically inflamed tissue that is usually infective.

Lipid Pneumonia - chronic condition caused by aspiration of oily substances into the lungs.


Melting Point - a temperature at which a material changes from a solid to a liquid upon heating.

Metastasis - transmission of a disease from one part of the body to another.

Methemoglobinemia -presence of methemoglobin in the bloodstream caused by the reaction of materials with the hemoglobin in red blood cells that reduces their oxygen-carrying capacity.

Mutagen - A material that induces genetic changes in the DNA of chromosomes. Mutagens may effects the future generations if sperm or egg cells are affected.


Narcosis - Sleeping or a state of unconsciousness caused by a chemical.

Nausea - tendency to vomit; feeling of sickness in the stomach.

Necrosis - localized death of tissue.

Neoplasm - new or abnormal tissue growth that is uncontrollable and progressive.

Nephrotoxic - poisonous to the kidney.

Neuritis - inflammation of the nerves.

Nystagmus - rapid, rhythmic, involuntary horizontal movements of the eyes.


Oliguria - scanty or low volume of urine.


Palpitation - irregular, rapid heartbeat.

PEL - (Permissible Exposure Limit) Established by OSHA. This may be expressed as a TWA, STEL, or CEL(C).

Percent Volatile - (%volatile/Volume) the percentage of a liquid or solid that evaporates at an ambient temperature of 70ºF (20ºC) unless another temperature is stated.

Phlegm - thick mucous from respiratory passage.

Photophobia - intolerable to light.

Physical State - condition of a material; i.e., solid, liquid or gas at room temperature.

Pneumoconiosis - respiratory tract and lung condition caused by inhalation and retention of irritant mineral or metallic particles.

Pneumonia - inflammatory lung disease caused by microorganisms, virus and chemical or physical irritants.

Polymerization - a chemical reaction in which one or more small molecules combine to form larger molecules.

Pour Point - the temperature at which a liquid either congeals or ceases to flow.

Precordial - in front of the heart, stomach.

Prostration - state of total mental or physical exhaustion

Proteinuria - presence of protein in the urine.

Psychotropic, PSY - acting on the mind.

Pulmonary Edema - fluid in the lungs.

Pyrophoric - Describes materials that ignite spontaneously in air below 54ºC(130°F).

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REL - Recommended Exposure Limits, NIOSH REL, is the highest allowable airborne concentration that is not expected to injure a worker. It may be expressed as a ceiling or TWA usually for 10 hr. shifts.

Respiratory system - breathing system, including the lungs.


Sclera - the tough, white, fibrous covering of the eyeball.

Sensitization - state of immune response reaction in which exposure to a material elicits an immune or allergic response.

Sensitizer - a material that on first exposure causes little or no reaction, but on repeated exposure may cause a marked response not necessarily limited to the contact site.

Siderosis - pneumoconiosis caused by inhalation of iron particles, or tissue pigmentation caused by contact with iron.

Silicosis - condition of massive fibrosis of the lungs causing shortness of breath because of prolonged inhalation of silica dusts.

Solubility in Water - a term expressing the percentage of a material that dissolves in water at ambient temperature.

Spasm - involuntary, convulsive muscular contraction.

Special Fire - Fighting Precautions-The proper methods, equipment and other information needed by fire personnel to safely engage a fire.

Specific Gravity - ratio of density of a substance to the density of a reference substance, at a specified temperature. Specific gravity is a dimensionless number. Water is the reference for solids and liquids, while air is the reference for gases.

STEL - Short Term Exposure Limits, or maximum concentration for a continuous exposure period of 15 minutes (with a maximum of four such periods per day, with at least 60 minutes between exposure periods, and the TLV-TWA is not exceeded.

Stomatitis - inflammation of the mucous membrane of the mouth.

Stupor -partial or near complete unconsciousness.

Synonyms - alternative names by which a material may be known.

Systemic Toxicity - adverse effects induced by a substance which affects the body in a general manner rather than locally.


Tachycardia - excessive rapid heartbeat, usually with a pulse rate above 100 beats per minute.

Tachypnea - increased rate of respiration.

Teratogen - A material or agent causing physical defects in a developing embryo or fetus.

Tinnitus -a ringing sound in the ears.

TLV - Threshold Limit Value. A term ACGIH uses to express the maximum airborne concentration of a material to which most workers can be exposed during a normal daily and weekly work schedule without adverse effects. Workers means healthy individuals; "healthy" is defined as a 150 lb. male, age 25-44. The young, old, ill, or naturally susceptible have lower tolerances and need to take additional precautions. TLV's. are expressed in 3 ways: C, TWA, STEL.

Trade secrets - This is confidential information that gives the owner an advantage over competitors. Manufactures may choose to withhold proprietary data from an MSDS. Typically these would be ingredients of a formulated product. OSHA permits this provided 1) the trade secret claim can be substantiated; 2) the MSDS indicates that data is being withheld, and 3) the properties and health effects are included.

TWA - Time Weighted Average. Usually expressed in exposure limits for 8hr per day or a 40 hr. work week.


Unusual Fire or Explosion Hazards - Unusual or unknown conditions or elements that may elevate the hazards in a fire.

Urticaria - hives caused by a systemic allergic reaction.


Vapor - the gaseous state of a material normally encountered as a liquid or solid.

Vapor Density - the ratio of the formula mass of the compound to the average formula mass of the gases in air. This formula ratio is correct for a pure gas at room temperature. However, this ratio does not accurately express the vapor density of a liquid solvent.

Vapor Pressure - the pressure a saturated vapor exerts above its own liquid in a closed container.

Vertigo - a feeling of revolving in space; dizziness, giddiness.

Viscosity - measurement of a fluid's thickness or resistance to flow.

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Zinc fume fever - caused by inhalation of zinc oxide fume and characterized by flu-like symptoms: metallic taste in mouth, coughing, weakness, fatigue, muscular pain, and nausea, followed by fever and chills. Symptoms occur 4-12 hours, post exposure.


% Volatile/Volume - the percentage of a liquid or solid that evaporates at an ambient temperature of 70ºF (20ºC) unless another temperature is stated.