Chemical Hygiene Definitions

Term Definition
Absorption To take a substance in across the exchange boundaries of an organism (skin, lungs, or gastrointestinal tract) and ultimately into body fluids and tissues.
ACGIH American Conference of Governmental Industrial Hygienists. An organization of professional personnel in governmental agencies or educational institution engaged in occupational safety and health programs. ACGIH develops and publishes recommended occupational exposure limits (see TLV) for hundreds of chemical and physical agents.
Acid A corrosive substance that produces destruction of skin tissue. Corrosive materials can have a very low pH or very high pH. See also Corrosive.
Acute Effect Adverse effect due to exposure to a harmful substance, whereby sever symptoms develop rapidly and lead quickly to a health crisis. These symptoms often subside when the exposure stops.
Administrative Control The use of management involvement, training of employees, rotation of employees, air sampling, biological sampling and medical surveillance to protect individuals.
Aerosol Solid or liquid particles of microscopic size dispersed in a gaseous medium, solid, or liquid, suspended in air (e.g. dust, fumes, fog and smoke).
Air-Line Respirator An atmosphere-supplying respirator in which the respirable gas is not designed to be carried by the wearer.
Air-Purifying Respirator A respirator in which ambient air is passed through an air-purifying element that removes the contaminant(s). Air is passed through the air-purifying element by means of the breathing action of the respirator wearer or by a blower.
Alkali A compound that has the ability to neutralize an acid and form a salt. Turns litmus paper blue and has pH values of 8 to 14. (Also known as “base, caustic”)
Allergen Any antigen (such as pollen, a drug or food) that induces an allergic state in humans or animals.
Allergic Reaction
  1. Reaction of the body to chemical and/or biological agents, characterized by bronchoconstriction, nasal congestion, tearing, sneezing, wheezing, coughing, itching rash and eruptions.
  2. Immune response following exposure to a foreign agent or substance in an individual who is hypersensitive to that substance as a result of prior exposures. Examples are some types of skin rashes and asthma.
Anesthetic A substance that causes loss of sensation or consciousness.
  1. A vapor or gas that can cause unconsciousness or death by suffocation (lack of oxygen). Most simple asphyxiants are harmful to the body only when they become so concentrated that they reduce oxygen in the air (normally 21%) to dangerous levels (18% or lower). Asphyxiation is one of the principal potential hazards of working in confined and enclosed spaces.
  2. A chemical that displaces oxygen in the air, potentially resulting in insufficient oxygen to sustain life, especially in poorly ventilated areas. A chemical asphyxiant chemically interferes with the body’s ability to take up and transport oxygen; a physical asphyxiant displaces oxygen in the environment.
Auto-Ignition Temperature The lowest temperature at which a flammable gas or vapor-air mixture will ignite from its own heat source or a contacted heated surface without necessity of spark or flame. Vapors and gases will spontaneously ignite at a lower temperature in oxygen than in air and their auto-ignition temperature may be influenced by the presence of catalytic substances.
Boiling Point
  1. The temperature at which a liquid changes to a vapor.
  2. The temperature at which the vapor pressure of a liquid equals the atmospheric pressure. The temperature at which the vapor pressure at the liquid-vapor interface.
Carcinogen A substance or agent capable of causing or producing cancer in mammals, including humans. A chemical is considered to be a carcinogen if
  • It has been evaluated by IARC and found to be a carcinogen or potential carcinogen
  • It is listed as a carcinogen or potential carcinogen in the Annual Report on Carcinogens published by the National Toxicology Program (NTP)
  • It is regulated by OSHA as a carcinogen.
CAA Clean Air Act. Federal law enacted to regulate/reduce air pollution. Administered by the EPA.
CAS Number Chemical Abstracts Service. An organization under the American Chemical Society. CAS abstracts and indexes chemical literature from throughout the world in “chemical Abstracts.” “CAS Numbers” are used to identify specific chemicals or mixtures.
Caustic A substance that is able to burn or corrode organic tissue by chemical action. See Acid and Corrosive.
Ceiling Limit The airborne concentration that should not be exceeded during any part of the working exposure.
CERCLA Comprehensive Environmental Response, Compensation and Liability Act of 1980.
CFR Code of Federal Regulations. A collection of regulations promulgated under U.S. law.
Chemical Family A group of single elements or compounds with a common general name. Example: acetone, methyl ethyl ketone (MEK) and methyl isobutyl ketone (MIBK) are of the “ketone” family; acrolein, furfural and acetaldehyde are of the “aldehyde” family.
Chemical Hygiene Plan Written documentation of a comprehensive chemical hygiene program in the laboratory, as required by the OSHA Laboratory Standard (29CFR1910.1450). Model Chemical Hygiene Plans are available from the USU EH&S Office.
Chemical Name The name given to a chemical in the nomenclature system developed by the International Union of Pure and Applied Chemistry (IUPAC) or the CAS. The scientific designation of a chemical or a name that will clearly identify the chemical for hazard evaluation.
Chronic Effect An adverse effect on a human or animal body, with symptoms which develop slowly over a long period of time.
Chronic Exposure Continuous or repeated contact with a toxic substance over a long period of time, generally over months or years.
CO Carbon monoxide. A colorless, odorless, flammable and very toxic gas produced by the incomplete combustion of carbon, also a by-product of many chemical processes.
CO2 Carbon dioxide. A heavy, colorless gas, produced by the combustion and decomposition of organic substances and as a by-product of many chemical processes. CO2 will not burn and is relatively non-toxic (although high concentrations, especially in confined spaces, can create hazardous oxygen-deficient environments).
Combustible Capable of catching fire or burning.
Combustible Liquid A liquid with a flash point at or above 37.8 °C (100 °F) but below 93.3 °C (200 °F)
Common Name Any designation or identification such as code name, code number, trade name, brand name or generic name used to identify a chemical other than by its chemical name.
Compressed Gas Gas or mixture of gases having, in a container, an absolute pressure exceeding 40 psi at 70 °F (21.2 °C) or a gas or mixture of gases having in a container, an absolute pressure exceeding 104 psi at 130 °F (54.5 °C) or a liquid having a vapor pressure exceeding 40 psi at 100 °F (37.8 °C) as determined by ASTM D-323-72.
Concentration The amount of a given substance in a stated unit of measure. Common methods of stating concentration are percent by weight or by volume; weight per unit volume; normality; etc.
Confined Space
  1. A space that is: one, large enough and so configured that an employee can bodily enter and perform assigned work; two, has limited or restricted means for entry or exit (for example, tanks, vessels, silos, storage bins, hoppers, vaults and pits are spaces that may have limited means of entry); and three, is not designed for continuous employee occupancy (See OSHA 1910.146).
  2. An enclosure that contains an oxygen deficiency, where the oxygen concentration is less than 19.5%. Examples are underground utility vaults, storage tanks and large diameter pipes.
  1. A chemical that causes visible destruction of or irreversible alterations in living tissue by chemical action at the site of contact.
  2. A chemical that causes necrosis of biological tissues.
Cryogenic Liquids are liquefied gases that have a normal boiling point below -150 °C (-238 °F). Liquid nitrogen has a boiling point of -195.8 °C (-320.5 °F). All cryogenic liquids produce large amounts of gas when they vaporize.
CWA Clean Water Act. Federal law enacted to regulate/reduce water pollution. Administered by the EPA.
Decomposition Breakdown of a material or substance (by heat, chemical reaction, electrolysis, decay, or other process) into parts, elements or simpler compounds.
Dermal Pertaining to the skin.
Dermal Absorption The transfer of contaminant across the skin and subsequent incorporation into the body.
Dermatitis Inflammation of the skin from any cause. There are two general types of skin reaction: primary irritation dermatitis and sensitization dermatitis.
Dot United States Department of Transportation. Regulates transportation of chemicals and other substances.
Dot Hazard Class DOT requires that hazardous materials offered for shipment be labeled with the proper DOT hazard class. These classes include corrosive, flammable liquid, peroxide, poison, etc. The DOT hazard class may not adequately describe all the hazard properties of the material.
Dust Solid particles that are capable of temporary suspension in air or other gases. Usually produced from larger masses through the application of physical forces (for example: handling, crushing, grinding, or rapid impact). Typical dusts are rock, ore, metal, coal, wood and grain.
Embryotoxin A material harmful to the developing embryo.
Engineering Controls Process change, substitution, isolation, ventilation, source modification.
Environmental Monitoring Program in which samples of air contaminants or energy measurements are taken and which establishes the level of worker exposure to such agents.
EPA United States Environmental Protection Agency. Primary agency responsible for the enforcement of federal laws protecting the environment.
Epidemiology The science that deals with the incidence distribution and control of disease in a population.
Evaporation Rate The rate at which a material is converted from the liquid or solid state to the vapor state; may be expressed relative to the evaporation rate of a known material, usually n-Butyl acetate (with an evaporation rate of 1.0 by definition). Faster evaporation rates are >1 and slower evaporation rates are 1.
Explosive A chemical causes a sudden, almost instantaneous release of pressure, gas, and heat when subjected to sudden shock, pressure, or high temperatures.
Explosive Limits Data on the MSDS that define the ranges of air-chemical mixtures that can explode when exposed to an ignition source; see Upper and Lower Explosive Limits.
Exposure As it pertains to air contaminants; it is the state of being exposed to a concentration of a contaminant.
Exposure Limit An air concentration limit established to prevent an adverse health effect.
Extinguishing Media The fire fighting substance to be used to control a material in the event of a fire. It is usually named by its generic name, such as fog, foam or water.
FIFRA Federal Insecticide, Fungicide and Rodenticide Act. Under this act regulations administered by the EPA require certain useful poisons, such as chemical pesticides, sold to the public contain labels that carry health hazard warnings to protect users.
Fire Hazard Chemical material that ignites and burns easily or that cause or supports fire in other materials; includes pyrophorics, flammables, combustibles, and oxidizers.
Flammability Limits The range of gas or vapor concentration in the air that may ignite or explode if an ignition source is present.
Flammable Liquid Any liquid having a flash point below 37.8 °C (100 °F).
Flammable Solid A solid, other than a blasting agent or explosive, as defined in 29CFR1910.109(a), that is liable to cause fire through friction, absorption of moisture, spontaneous chemical change, or retained heat from manufacturing processing or which can be ignited readily and when ignited burns so vigorously and persistently as to create a serious hazard.
Flash Point The temperature at which the vapor above a volatile liquid forms a combustible mixture with air.
Fume Minute solid particles generated by condensation from the gaseous, generally after volatilization (evaporation) from melted substances, such as welding and often accompanied by a chemical reaction, such as oxidation.
Gas Any material in the gaseous state at 25 °C and 760 mmHg. Normally, a formless fluid, it expands to fill the space or enclosure. Gases can be changed to the liquid or solid state only by the combined effect of increased pressure and decreased temperature.
General Ventilation Ventilation systems designed primarily for temperature, humidity, and odor control; health hazard protection is secondary.
Hazard Evaluation Evaluation based on data concerning concentration of a contaminant and duration of exposure.
HAZCOM Program Hazard Communication Program. Written document that describes how an employer or facility complies with all requirements of the Federal Hazard Communication Standard
HAZCOM Standard Hazard Communication Standard. Federal law developed by OSHA to reduce illness and injury caused by chemical hazards in the workplace. Requires evaluation of chemical hazards and communication of hazard information to both employers and employees.
Hazard Identification Determining whether a chemical can cause adverse health effects in humans and what those effects might be.
Hazardous Chemical Inventory List of all hazardous chemicals known to be present in each workplace.
Hazardous Ingredients The hazardous substances that make up a mixture.
Hazardous Materials Any substance or material that could adversely affect the safety of the public, handlers, or carriers during transportation.
Hazardous Polymerization Polymerization is a chemical reaction in which one or more small molecules combine to form larger molecules. A hazardous polymerization is such a reaction which takes place at a rate which releases large amounts of energy. If hazardous polymerization can occur with a given material, the MSDS usually will list conditions which could start the reaction and since the material usually contains a polymerization inhibitor, the expected time period before the inhibitor is used up.
Hazardous Waste Under RCRA, any solid or combination of solid and liquid waste, which because of its physical, chemical, or infectious characteristics may pose a hazard when improperly handled.
Health Hazard A chemical for which there is statistically significant evidence based on at least one study conducted in accordance with established scientific principles that acute or chronic health effects might occur in exposed individuals. The term “health hazard” includes chemicals that are carcinogens, toxic or highly toxic agents, reproductive toxins, irritants, corrosives, sensitizers, hepatotoxins, nephrotoxins, neurotoxins, agents that act on the hematopoietic system and agents that damage the lungs, skin, eyes or mucous membranes.
Health Physicist A radiation scientist, engineer or physician concerned with the research, teaching, or operational aspects of radiation safety. The role of the health physicist is to specify safe radiation levels for the environment, occupational exposures, industry, research, and medicine and to react to variances in these cases.
Housekeeping An administrative control that involves containing and removing chemical hazards trough good work practices such as proper chemical storage, keeping aisles and walkways clear, and regular cleaning of work surfaces.
IARC International Agency for Research on Cancer
IDLH Immediately Dangerous to Life and Health. Any atmosphere that poses an immediate hazard to life or poses immediate irreversible debilitating effects on health. A term used to describe a very hazardous environment, usually with high concentrations of toxic chemicals, insufficient oxygen, or both.
Ignitable Capable of being set afire.
Immediate Effect Health effect that appears right away-either during the exposure or shortly after.
Incompatible Materials which could cause dangerous reactions from direct contact with one another are described as incompatible.
Industrial Hygienist Expert in the recognition, evaluation, and control of safety and health hazards.
Inflammable Same as flammable.
Ingestion One of the four primary routes of exposure. The way that a chemical enters your body if you swallow it.
Inhalation One of the four primary routes of exposure. The way that a chemical enters your body when you breathe it through your nose of mouth.
Irritant A chemical, which is not corrosive, that causes a reversible inflammatory effect on living tissue by chemical action at the site of contact. Symptoms include: reddening, itching, tearing, and irritation.
Laboratory Standard Regulation passed by OSHA which governs chemical hygiene in laboratories. This standard is formally referred to as 29 CFR 1910.1450, “Exposure to Hazardous Chemicals in the Laboratory.”
LC50 Lethal concentration 50%. The concentration of a material in air which, on the basis of laboratory tests, is expected to kill 50% of a group of test animals when administered as a single exposure (usually 1 to 4 hours). The LC50 is expressed as parts per million parts of air, by volume (ppm) for gases and vapors, or micrograms or milligrams per cubic meter of air (ug/m3, mg/m3) for dusts and mists.
LD Lethal dose. A concentration of a substance being tested which will kill a test animal.
LD50 Lethal dose 50%. A single dose of a material which on the basis of laboratory tests is expected to kill 50% of a group of test animals. The LD50 dose is usually expressed as milligrams or grams of material per kilogram of animal body weight (mg/kg or g/kg). If a material has a low LD50, then only a very small amount is needed to cause an adverse effect and that substance would be considered highly toxic.
LEL Lower Explosion Limit or lower flammable limit of a vapor of gas. The lowest concentration (lowest percentage of the substance in air) that will produce a flash of fire when an ignition source (heat, arc, or flame) is present. At concentrations lower than the LEL, the mixture is too “lean” to burn.
Local Effect When effects of chemical exposure occur directly at the point of contact the material is said to have a local effect.
Local Exhaust Ventilation An industrial ventilation system that captures and removes emitted contaminants before dilution into the workplace ambient air can occur.
Medical Monitoring Type of administrative control that involves physical examinations and/or lab tests to establish an individual’s baseline health status and check the effectiveness of other controls used to protect an individual from health hazards.
Melting Point For a given pressure, the temperature at which the solid and liquid phases of the substance are in equilibrium.
Mg/Kg A way expressing dose, milligrams (mg) of substance per kilogram (kg) of body weight. Example: a 100 kg person given 10,000 mg of a substance would be getting a dose of 100 mg/kg.
Mist A dispersion of suspended liquid particles, many large enough to be individually visible to the unaided eye. Generated by condensation from the gaseous to the liquid state or by breaking up a liquid into a dispersed state such as splashing, foaming, or atomization.
MSDS Material Safety Data Sheet. Contains specific health and safety information required by the Federal Hazard Communication Standard for any hazardous substance. There is no standard format for a MSDS. They will vary in length, format and appearance depending on the manufacturer or supplier, who must provide an MSDS for each hazardous chemical they produce.
Mutagen A substance or agent capable of altering the genetic material in a living cell.
NFPA National Fire Protection Association. An international voluntary membership organization to promote/improve fire protection and prevention and establish safeguards against losses of life and property by fire. Best known on the industrial scene for the National Fire Codes- volumes of codes, standards, recommended practices, and manuals developed and updated by NFPA technical committees.
NIOSH National Institutes for Occupational Safety and Health. Established by the occupational Safety and Health Act of 1970, NIOSH is part of the Centers for Disease Control and Prevention within the U.S. Department of Health and Human Services. NIOSH traces its origins to 1914 when the U.S. Public Health Service organized a division of Industrial Hygiene and Sanitation. NIOSH’s responsibilities include research and recommending occupational health and safety standards.
Nonflammable Not easily ignited, or if ignited, not burning readily.
NRC This acronym may be used to refer to the following: Nuclear Regulatory Agency, National Response Center, or National Research Council.
NTP National Toxicology Program. Overseen by the U.S. Department of Health and Human Services. This organization funds and conducts research on chemical substances. NTP publishes lists of carcinogens and potential carcinogens; this list is one of the reference sources that must be used to identify cancer causing chemicals on MSDSs.
Olfactory Relating to the sense of smell. The olfactory organ in the nasal cavity is the sensing element that detects odors and transmits information to the brain through the olfactory nerves.
Organic Peroxide An organic compound that contains the bivalent –O-O structure and may be considered a structural derivative of hydrogen peroxide where one or both hydrogen atoms has been replaced by an organic radical. Some organic peroxides are highly unstable and may decompose with explosive force.
OSHA Occupational Safety and Health Administration. Established by the OSH Act of 1970, OSHA is located within the U.S. Department of Labor. The agency’s responsibilities include promulgating occupational safety and health standard and inspecting workplaces to ensure compliance with these standards.
Oxidizer A chemical other than a blasting agent or explosive that initiates or promotes combustion in other materials, thereby causing fire either of itself or through the release of oxygen or other gases. Chlorate (ClO3), permanganate (MnO4), and nitrate (NO3) compounds are examples of oxidizers.
PEL Permissible Exposure Limit. The legally enforce exposure limit for a substance established by OSHA regulatory authority. The PEL indicates the permissible concentration of air contaminants to which nearly all workers may be repeatedly exposed eight (8) hours a day, forty (40) hours a week, over a working lifetime (30 years) without adverse health effects.
Ph The symbol relating the hydrogen ion (h) concentration to that of a given standard solution. A pH of 7 is neutral. Numbers increasing from 7 to 14 indicate greater alkalinity. Numbers decreasing from 7 to 0 indicate greater acidity.
Physical Hazard A chemical for which there is scientifically valid evidence that it is a combustible liquid, a compressed gas, explosive, flammable, an organic peroxide, an oxidizer, pyrophoric, unstable (reactive), water reactive, or cryogenic.
Poison (Class A) A DOT hazard class for extremely dangerous poisons, that is, poisonous gases or liquids of such nature that a very small amount of the gas, or vapor of the liquid mixed with air is dangerous to life. Some examples: phosgene, cyanogen, hydrocyanic acid, nitrogen peroxide.
Poison (Class B) A DOT hazard class for liquid, solid, paste, or semi-solid substances (other than Class A poisons or irritating materials) which are known (or presumed) on the basis of animal tests to be so toxic to man as to afford a hazard to health during transportation. Some examples: arsenic, beryllium chloride, cyanide, mercuric oxide.
PPE Personal Protective Equipment. Equipment that protects the individual who wears it by placing a barrier between that individual and a hazard; includes protective eye wear, face shields, gloves, boots, hard hats, clothing, and respirators.
PPM Parts per million. An expression of concentration as a volume ratio, usually parts of contaminant per million parts of air.
Pyrophoric Capable of spontaneously igniting in air.
RACC Research Agents Containment Center. USU’s hazardous chemical and radioactive waste collection, segregation, and packaging facility.
RCRA Resource Conservation and Recovery Act. Regulates the management and disposal of hazardous materials and waste currently being generated, treated, stored, or distributed.
Reactivity A description of the tendency of a substance to undergo chemical reaction with the release of energy. Undesirable effects; such as, pressure build up, temperature increase, formation of noxious, toxic, or corrosive by products may occur because of the reactivity of a substance to heating, burning, direct contact with other materials or other conditions in use or in storage.
Reproductive Hazard Health hazard that targets the human reproductive system; health hazard category that includes teratogens and mutagens.
Routes Of Entry The means be which a chemical enter the body (e.g. ingestion, inhalation, dermal absorption, or injection).
SCBA Self Contained Breathing Apparatus. A respiratory protection device that consists of a supply of respirable air and designed to be carried by the wearer.
Sensitizer A foreign agent or substance that is capable of causing an immune response in an individual. In most cases, initial exposure results in a normal response, but repeated exposures lead to progressively strong and abnormal response.
Skin A notation, sometimes used with PEL and TLV exposure data; indicates that the stated substance may be absorbed by the skin, mucous membranes, and eyes - either airborne or by direct contact - and that this additional exposure must be considered part of the total exposure to avoid exceeding the PEL or TLV for that substance.
Skin Absorption Ability of some hazardous chemicals to pass directly through the skin and enter the bloodstream.
Smoke A mixture of dry and liquid particles generated by incomplete combustion of an organic material, combined with, and suspended in the gases from combustion.
Solubility The amount of a substance that can be dissolved in a solvent, usually water.
Solvent A substance that dissolves other substance, most commonly water but often an organic compound.
Specific Gravity The weight of a material compared with the weight of an equal volume of water is an expression of the density (or heaviness) of a material. Insoluble materials with a specific gravity of less than 1.0 will float in (or on) water. Insoluble materials with a specific gravity greater than 1.0 will sink in water.
Spill Procedures The methods, equipment, and precautions that should be used to control or lean up a leak or spill.
Splash Proof Goggles Eye protection made on a non-corrosive material that fits snugly against the face and has indirect ventilation ports.
Stability An expression of the ability of a material to remain unchanged. For MSDS purposes, a material is stable if it remains in the same form under expected and reasonable conditions of storage or use. Conditions which may cause instability (dangerous change) are stated - examples, temperatures above 150 °F, shock from dropping, and etc.
STEL Short Term Exposure Limit. Maximum concentration for continuous 15-minute period. Allowed four times a day, with at least 60 minutes between exposures. Used in reference to the OSHA PEL-STEL and ACGIH’s TLV-STEL. STELs are recommended when exposures of even short duration to high concentrations of a chemical are known to produce acute toxicity.
Substitution Engineering control that involves replacing a chemical, process, or piece of equipment with a less hazardous one.
Supplied-Air Respirators Air line respirators or self-contained breathing apparatus (SCBA).
Systemic Effect When a toxic effect occurs at a body part some distance from the point of contact, the substance is said to have a systemic effect.
Target Organ Toxin A toxic substance that attacks a specific organ of the body. For example, overexposure to carbon tetrachloride can cause liver damage.
Teratogen A substance or agent to which exposure of a pregnant female can result in malformations in the fetus.
Thermal Involving heat.
TLV Threshold Limit Value. A term used by ACGIH to express the airborne concentration of a material to which nearly all persons can be exposed day after day, without adverse effects.
Toxic Substance Any substance which can cause acute or chronic injury
Toxicity A relative property of a chemical agent; refers to a harmful effect on some biologic mechanism and the condition under which this effect occurs.
Toxicology Scientific study of poisons, their actions, their detection, and the treatment of conditions produced by them.
Trade Secret Any confidential formula, pattern, process, device, information, or compilation of information that is used in an employer’s business and that gives the employer an opportunity to obtain an advantage over competitors who do not know or use it.
TWA Time Weighted Average. Average exposure for an individual over a given working period, as determined by sampling at given times during the period. This is fundamental concept of most occupational exposure limits. It is usually presented as the average concentration over an 8-hr workday for a 40 hour work week.
UEL Upper Explosive Limit. The percentage by volume of a flammable gas or vapor that is the maximum level that will ignite when an ignition source (heat, arc, or flame) is present. Also referred to as the “upper flammable limit”.
UN Number A registry number assigned to dangerous goods by the United Nations Committee of Experts on the Transport of Dangerous Goods. This UN number is required in shipping documentation and on packaging as part of the DOT regulations for shipping hazardous materials.
Unstable A chemical which in the pure state, or as produced or transported, will vigorously polymerize, decompose, condense, or will become self-reactive under conditions of shock, pressure, or temperature. These chemicals are also referred to as reactive.
Vapor Density The weight of a vapor or gas compared to the weight of an equal volume of air is an expression of the density of the vapor or gas. If the vapor or gas is more dense than air (vapor density >1) it will sink. If the vapor of gas is less dense than air (vapor density 1) it will rise.
Vapor Pressure The partial pressure exerted by the airborne molecules of a compound that is in equilibrium with its liquid. To be in equilibrium means that concentration does not change; thus the rate at which molecules are leaving the liquid (evaporating must be equal to the rate at which airborne molecules are being reabsorbed back into the liquid. Vapor pressure is a direct indicator of a chemical’s volatility.
Ventilation The process of supplying or removing air by natural or mechanical means to or from any space. Such air may or may not be conditioned.
Viscosity The tendency of a fluid to resist internal flow without regard to its density.
VOC Volatile Organic Compound. Any organic compound that participates in atmospheric chemical reactions.
Volatility A measure of how quickly a substance forms vapor at ordinary temperatures.
Water Reactive A chemical that reacts with water to release a gas that is either flammable or presents a health hazard. Also denoted, dangerous when wet.