MSDS / SDS Glossary

For the benefit of MSDS Authoring Services’ valued GHS MSDS clients, the most frequently used MSDS terms and definitions found in material safety data sheet information, MSDS data sheets, MSDS solutions, and MSDS forms have been compiled in the below glossary. If you are in need of MSDS writing, MSDS authoring, MSDS updating, or MSDS editing services, MSDS Authoring Services is your ultimate source for GHS-compliant Material Safety Data Sheets of the highest quality and accuracy.


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ABSOLUTE: Chemical substance that is relatively free of impurities. Often found in MSDS data sheets.

ABSOLUTE PRESSURE: The sum of the available pressure within a vessel, pipe, etc., and the gauge pressure in the pumping system.

ABSORPTION: To take in and make a part of an existing whole. The penetration of a solid substance by a liquid as by capillary, osmotic, solvent or chemical action.

ACGIH: ACGIH is the American Conference of Governmental Industrial Hygienists. An organization of professionals in governmental agencies or educational institutions engaged in occupational safety and health programs. ACGIH develops and publishes recommended occupational exposure limits for chemical substances and physical agents.

ACID: Any chemical compound which is dissolved in water with the formation of hydrogen ions. Acids have a sour taste and may cause severe burns. They turn litmus paper red and have ph values of 0 to 6. Acids will neutralize bases or alkaline media. Acids are a substance also found in MSDS information.

ACTION LEVEL: Exposure level at which OSHA regulations to protect employees takes effect. Exposure at or above the action level is termed occupational exposure. Exposure below this level can also be harmful.

ACTIVE INGREDIENT: Ingredient of a product that actually does what the product is designed to do. The remaining ingredients may be inert.

ACUTE EFFECT: Adverse symptoms or effects on a human or animal that take place soon after exposure to a chemical.

ACUTE TOXICITY: Adverse effects resulting from a single dose of or exposure to a substance.

ADSORB: Collect gas or liquid molecules on the surface of another material found in MSDS data sheets.

ADHESION: A union of two surfaces that are normally separate.

AEROSOL: Fine aerial suspension of liquid (mist, fog) or solid (dust, fume, smoke) particles small enough to be stable.

AGENT: Most MSDS services will provide agents which are any substance, force, radiation, organism, or influence that affects the body. Effects may be beneficial or injurious.

ALARA: Acronym for “as low as reasonably achievable.”

ALKALI: Any chemical substance which forms soluble soaps with fatty acids. Alkalis are also referred to as bases. May cause severe burns to the skin. Alkalis turn litmus paper blue and have pH values from 8 to 14.

ALLERGIC REACTION: Abnormal physiological response a person gets to a chemical or physical stimuli.

AMBIENT: Usual or surrounding environment.

AMENORRHEA: Absence of menstruation.

AMES TEST: Short term test commonly used for preliminary screening of chemicals to see if they cause mutations in a special type of bacterial cell.

ANALGESIA: Loss of sensitivity to pain.

ANESTHETIC: Chemical found in Material Safety Data Sheet information that causes a total or partial loss of sensation. Overexposure to anesthetics can cause impaired judgment, dizziness, drowsiness, headache, unconsciousness, and even death.

ANHYDRIDE: Compound derived from other compound by removing elements composing water (hydrogen and oxygen).

ANHYDROUS: Substance in which no water molecules are present as hydrate or as water crystallization.

ANOXIA: Lack of oxygen from inspired air.

API: American Petroleum Institute is an organization of the petroleum industry.

APPEARANCE: Physical state or condition of a material that exists in a material safety data sheet.

AQUEOUS: Water-based solution or suspension. Frequently, a gaseous compound dissolved in water commonly found in MSDS data sheets.

ASPHYXIANT: Vapor or gas which causes unconsciousness or death by suffocation. Most simple asphyxiants are harmful to the body only when they become so concentrated that they reduce oxygen in air (normally 21%) to dangerous levels (16% or lower). Asphyxiation is a potential hazard of working in confined spaces. Some chemicals like Carbon Dioxide function as chemical asphyxiants by reducing the blood’s ability to carry oxygen.

ASTM: American Society for Testing and Materials.

ATMOSPHERE (atm.): Pressure measurement. One atmosphere (atm) = 14.7 lbs/sq in.

AUTOIGNITION TEMPERATURE: Minimum temperature which a substance, (that are often found in Material Safety Data Sheets) must be heated without application of flame or spark to cause substance to ignite. Materials should not be heated to greater than 80% of this temperature.


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BASE: Substances that (usually) liberate OH anions when dissolved in water. Bases react with acids to form salts and water. Strong bases have a pH greater than 7, turn litmus paper blue, and may be corrosive to human tissue. A strong base is called alkaline or caustic and is usually found in material safety data writing or authoring sheets.

BAUME: Arbitrary scale of specific gravities; used to determine specific gravities and in graduation of hydrometers.

BENIGN: Not recurrent or not tending to progress. Not cancerous.

BIODEGRADABLE: By the action of living things, something that is capable of being broken down into non harmful products

BOILING LIQUID EXPANDING VAPOR EXPLOSION (BLEVE): Condition in which liquids are excessively heated, which may result in the violent rupture of a container, and the rapid vaporization of the material. The possibility of a BLEVE increases with the volatility of the material.

BOILING POINT (BP): Temperature at which a liquid, that could possibly be found in a material safety data sheet, changes to a vapor state at a given pressure. Flammable materials with low boiling points generally present special fire hazards.

BUFFER: Substance commonly existing in most companies MSDS data sheets, which reduces the change in hydrogen ion concentration (pH) that otherwise would be produced by adding acids or bases to a solution.

BULK DENSITY: The mass (weight) per unit volume of a solid particulate material as it is normally packed, with voids between particulates containing air.

BUNA: Trademark for synthetic rubber and rubberlike materials such as Buna-N (Nitrile) or Buna-S (Styrene).


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C: Centigrade, a unit of temperature.

CALORIE: A calorie is the amount of heat required to raise 1 gram of water 1 degree C. Standard unit of heat.

CARBON DIOXIDE: Commonly provided by most MSDS services, carbon dioxide is (CO2) heavy, colorless gas produced by combustion and decomposition of organic substances and as by-product of chemical processes.

CARBON MONOXIDE: An ingredient found in most chemical MSDS data sheets. Carbon monoxide is (CO) colorless, odorless, flammable, and very toxic gas produced when carbon burns with insufficient air.

(CAS) CHEMICAL ABSTRACTS SERVICE NUMBER: CAS numbers identify specific chemicals, an assigned number used to identify a chemical. CAS stands for Chemical Abstracts Service, an organization that indexes information published in Chemical Abstracts by the American Chemical Society and that provides index guides by which information about particular substances may be located in the abstracts.

CATALYST: Substance often found in most company MSDS sheets, that modifies a chemical reaction (makes it faster or slower) without being consumed.


CC: Closed cup. Identifies one of the methods used to measure flash points of flammable liquids.

cc, cm3: Cubic centimeter.

CENTIPOISE: cgs unit of the measure of viscosity equal to 1/100 poise. The viscosity of water at 20C is approximately 1 centipoise.

CENTIMETER, cm: 1/100 meter. A cm = approximately 0.4 in.

cgs: Metric units of measure based upon centimeter, gram, and second.

CHELATING AGENT: A chemical compound capable of forming multiple chemical bonds to a metal ion. Used to treat metal poisoning and found in most MSDS information.

CHEMICAL: Any element, chemical compound, or mixture of elements or compounds. Chemicals are found in material data safety sheets created by authoring and writing MSDS sheet companies.

CHEMICAL FAMILY: Group of single elements or compounds with a common general name.

CHEMICAL FORMULA: Gives the number and kinds of atoms that comprise a molecule of a material.

CHEMICAL NAME: Scientific designation of name that clearly identifies chemical for hazard evaluation purposes. Chemical names are found in company MSDS sheets.

CHEMICAL REACTIVITY: Ability of a material to chemically change.

CHEMTREC®: 24-hour toll-free telephone number (800-424-9300), intended primarily for use by those who respond to chemical transportation emergencies. (CHEMTREC® is a registered service mark of the American Chemistry Council, Inc.). MSDS Authoring Services and its parent company NuGenTec no longer have any affiliation with Chemtrec.

CHRONIC EFFECT: Adverse effect on a human or animal body with symptoms that develop slowly over a long period of time or that recur frequently. An example of chronic effect would be cancer due to sun exposure.

CHRONIC EXPOSURE: Long-term contact with a substance.

CHRONIC TOXICITY: Adverse effects resulting from repeated doses of or exposures to a material over a relatively prolonged period of time.

COMBUSTIBLE LIQUIDS: Term used by NFPA and DOT to classify certain liquids that will burn, on the basis of flash points. They do not ignite as easily as flammable liquids, but they can be ignited under certain conditions, and must be handled with caution.

COMMON NAME: Designation for material other than chemical name, such as code, trade, brand, or generic name. Common Names are included in MSDS information.

COMPRESSED GAS: Most Material Safety Data Sheet services will provide compressed gas which is a material contained under pressure.

CONCENTRATION: When a substance is combined or mixed with other substances.

CONFINED SPACE: An area that has limited openings for entry and exit and would make escape difficult in an emergency, has a lack of ventilation, contains known and potential hazards, and is not intended nor designated for continuous human occupancy.

CORROSION RATE: Expressed in inches per year; accompanied by temperature.

CORROSIVE: Liquid or solid that causes visible destruction or irreversible alterations in skin tissue at site of contact, or, in the case of leakage from its packaging, liquid that has severe corrosion rate on steel.

CRITICAL PRESSURE/TEMPERATURE: Temperature above which a gas cannot be liquefied by pressure. The critical pressure is the pressure required to liquefy a gas at its critical temperature.

CRYOGENIC: Relating to extremely low temperature as for refrigerated gases.

cu ft, ft3: Cubic foot. Cu ft is more usual.

cu m, m3: Cubic meter. m3 is preferred.


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DANGEROUSLY REACTIVE MATERIAL: Material that can react by itself or with water/air producing hazardous condition.

DECOMPOSITION: Breakdown of a material or substance into parts or elements or simpler compounds.

DEFATTING: Removal of natural oils from the skin by fat-dissolving solvents or other chemicals. Solvents and chemicals are provided in Material Safety Data Sheets.

DELIQUESCENT: Frequently found in most MSDS solutions, deliquescent are water soluble salts that absorb moisture from air and to soften or dissolve as a result. Usually in powdered form.

DEMULCENT: Material capable of soothing or protecting inflamed, irritated mucous membranes.

DENSITY: Ratio of weight to volume of a material, usually in grams per cubic centimeter.

DEPRESSANT: A substance that reduces a bodily functional activity or an instinctive desire, such as appetite.

DILUTION VENTILATION: Airflow designed to dilute contaminants to acceptable levels.

DRY CHEMICAL: Powdered fire extinguishing agent, usually composed of sodium bicarbonate, potassium bicarbonate, etc. most Material Safety Data Sheets contain dry chemicals.


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EFFECTIVE CONCENTRATION (EC50): Concentration of a material in water, a single dose which is expected to cause a biological effect on 50% of a group of test animals.

ELECTROLYTE: Non-metallic substance that conducts electric current in solution by moving ions rather than electrons.

EMETIC: Agent that induces vomiting. Agents along with chemicals and compounds are found in most MSDS authoring sheets.

ENDOTHERMIC: A chemical reaction that absorbs heat.

EVAPORATION RATE: Rate at which a particular material will vaporize. Evaporation rate can be useful in evaluating the health and fire hazards of a material.

EXPLOSIVE: Material that produces a sudden, almost instantaneous release of pressure, gas, and heat when subjected to abrupt shock, pressure, or high temperature.

EXPOSURE OR EXPOSED: State of being open and vulnerable to a hazardous chemical by inhalation, ingestion, skin contact, absorption, or any other course.

EXPOSURE LIMITS: Concentration in air of a chemical that can be familiar in Material Safety Data Sheets, that is thought to be acceptable.


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FIBER: Found in Material Safety Data Sheets, fiber is a basic form of matter, with a high ratio of length to diameter.

FIRE POINT: Lowest temperature at which liquid will produce sufficient vapor to flash near its surface and continue to burn.

FLASH BACK: Occurs when a trail of flammable material is ignited by a distant spark or ignition source. When this occurs the flame travels along the path back to its starting pointing.

FLASH POINT: Temperature at which a liquid will give off enough flammable vapor to ignite.

FOAM: Material consisting of small bubbles of air, water, and concentrating agents. Used for firefighting. Foam is a material found in some Material Safety Data Sheets.

FOG: Visible suspension of fine droplets in a gas.

FORESEEABLE EMERGENCY: Potential occurences such as equipment failure, rupture of containers, or failure of control equipment which could result in an uncontrolled release of a hazardous chemical.

FORMULA: The scientific expression of the chemical composition of a material (e.g., water H2O, sulfuric acid H2SO4, sulfur dioxide is SO2).

FREEZING POINT: Temperature at which a material changes its physical state from liquid to solid.

FUGITIVE EMISSION: Gas, liquid, solid, vapor, fume, mist, fog, or dust that escapes from process equipment or a product.

FUME: A particulate that is smoke-like emanation from the surface of heated metals. This heating is often accompanied by a chemical reaction where the particles react with oxygen to form an oxide.


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GAS: Formless fluid that occupies the space of its enclosure that possess perfect molecular mobility. Gas is commonly found in most chemical and gas company MSDS sheets.

GENERIC NAME: A designation or identification used to identify a chemical by other than its chemical name (e.g., code name, code number, trade name, brand name) present in Material Safety Data Sheets.

GHS (Globally Harmonized System): The Globally Harmonized System of Classification and Labeling of Chemicals (GHS) is an international consensus system for classifying and labeling hazardous chemicals. The GHS is designed to streamline the hazard assessment, labeling, and hazard communication requirements within and between the countries that adopt it by promoting common, consistent criteria for classifying chemicals according to their health, physical and environmental hazards, and to develop compatible labeling. Material Safety Data Sheets (MSDS) and other information based on those classifications. GHS will resolve many, but not all, differences between MSDS information and labels between, for example, the US, Canada, and the European Union.

GRAM: Metric unit of mass weight. One U.S. ounce is about 28 grams and one pound is 454 grams.

GRAM/KILOGRAM: Expression of dose used in oral and dermal toxicology testing to indicate the grams of substance dosed per kilogram of animal body weight.


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HAZARDOUS DECOMPOSITION: Breaking down or separation of a substance into its constituent parts, elements, or into simpler compounds.

HAZARDOUS CHEMICAL: Hazardous chemicals are frequently found in MSDS sheets and are any chemical whose presence or use is a physical hazard or a health hazard.

HAZARDOUS INGREDIENTS: Hazardous substances that make up a mixture. These ingredients often make up solids, liquids, and gases that are written in Material Safety Data Sheets.

HAZARDOUS MATERIAL: Any substance or mixture of substances having properties capable of producing harm to people, animals, or other living organisms.

HEALTH HAZARD: Chemical from which acute or chronic health effects may occur in exposed individuals based on significant evidence.

HIGHLY TOXIC: Most MSDS writers provide information about highly toxic chemicals, which are chemicals in any of the following categories:

  • A chemical with a median lethal dose (LD50) of 50 milligrams or less per kilogram of body weight when administered orally to albino rats between 200 and 300 grams each.
  • A chemical with a median lethal dose (LD50) of 200 milligrams or less per kilogram of body weight when administered by continuous contact for 24 hours (or less if death occurs within 24 hours) with the bare skin of albino rabbits weighing between 2 and 3 kilograms each.
  • A chemical that has a median lethal concentration (LC50) in air of 200 parts per million by volume or less of gas or vapor, or 2 milligrams per liter or less of mist, fume, or dust when administered by continuous inhalation for 1 hour (or less if death occurs within 1 hour) to albino rats weighing between 200 and 300 grams each.
  • Highly toxic chemicals are found in Material Safety Data Sheets written and authorized by MSDS authoring companies.

HYDROCARBON: Organic compound composed only of carbon and hydrogen and is a compound frequently found in MSDS sheets.

HYDROPHILIC: Materials that have large molecules that absorb and retain water, causing them to swell and frequently to gel. These materials also are often written in MSDS sheets.

HYGROSCOPIC: Readily adsorbing available moisture in any form.


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IMPERVIOUS: A material that does not allow another substance to pass through or penetrate it. Often provided by a Material Safety Data Sheet writer.

INCOMPATIBLE: Materials which could cause dangerous reactions from direct contact with one another. Some of these reactions include fire or explosion.

INERT INGREDIENTS: Anything other than the active ingredient in a product; not having active properties.

INFLAMMABLE: Capable of being easily set on fire and continuing to burn, especially violently.

INHALATION: Breathing in of a substance in the form of a gas, vapor, fume, mist, or dust.

INHIBITOR: Most MSDS authorizing services will provide inhibitor which is, Chemical which is added to another substance to prevent an unwanted chemical change from occurring.

INORGANIC MATERIALS: Compounds found in MSDS sheets, derived from other than vegetable or animal sources; generally do not contain carbon atoms.

INSOLUBLE: Being dissolved into a liquid is not possible.

IRRITANT: By contact in sufficient concentration for a sufficient period of time, an irritant is a chemical that causes a reversible inflammatory effect.

ISOMERS: Compounds that have same molecular weight and atomic composition but differ in molecular structure. Most MSDS services will provide isomers within the Material Safety Data Sheets themselves.


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KILOGRAM: Metric unit of weight; about 2.2 pounds.


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LOCAL EFFECTS: Toxic or irritation effects, which occur at the site of contact with a chemical or substance.

LOCAL VENTILATION: Drawing off and replacement of contaminated air directly from its source.

LOWER EXPLOSIVE (FLAMMABLE) LIMIT (LEL): Lowest concentration that will produce a flash of fire when an ignition source (heat, electric arc, or flame) is present.


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MELTING POINT: The temperature when a substance changes to a liquid state.

METER: A unit of length, equivalent to 39.37 inches.

MIST: Suspended liquid droplets generated by condensation from the gaseous to the liquid state.

MIXTURE: Any combination of two or more chemicals.

MOLECULAR WEIGHT: Weight (mass) of a molecule based on the sum of the atomic weights of the atoms that make up the molecule.

MSDS: Material Safety Data Sheet, a document or service providing information and instructions on the chemical and physical characteristics of a substance, its hazards and risks, safe handling requirements and the actions to be taken in the event of fire, spill or exposure. Most MSDS providers use expert writers and writing services.


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n-: Normal. Used as a prefix in chemical names signifying a straight-chain structure.

NEUTRALIZE: Either by adding an acid to a base or by adding a base to an acid to neutralize is the process of bringing the pH to between 5 and 8 in acid based chemistry.

NON-FLAMMABLE: Not capable of being easily ignited or burning with extreme speediness when lighted.


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ORGANIC MATERIALS: Compounds composed of carbon, hydrogen, and other elements with chain or ring structures.

OVEREXPOSURE: Exposure to a hazardous substance beyond the normal exposure levels.

OXIDATION: Reaction in which a substance combines with oxygen provided by an oxidizer or oxidizing agent.

OXIDIZER: Substance that yields oxygen readily to stimulate the combustion of organic matter often provided by MSDS writers.

OXIDIZING AGENT: Chemical or substance that brings about an oxidation reaction.


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PARTICULATE: Small, separate pieces of an airborne material. Generally, anything that is not a fiber and has an aspect ratio of 3 to 1. Often found on MSDS sheets.

PARTS PER MILLION (PPM): Unit for measuring concentration of a gas or vapor in air. Also used to indicate the concentration of a particular substance in a liquid or solid.

PERCENT VOLATILE: Percent volatile by volume is the percentage of a liquid or solid (by volume) that will evaporate at an ambient temperature of 70 degrees F (unless some other temperature is specified).

PETROLEUM DISTILLATE: Complex mixture of hydrocarbons, liquid at normal ambient conditions, separated from crude oil and other refinery process streams by distillation.

PHYSICAL STATE: Condition of a material (solid, liquid, or gas) at room temperature. Most Material Safety Data Sheet writers will provide materials with a physical state.

POLYMERIZATION: Chemical reaction in which one or more small molecules combine to form larger molecules.

psia: Pounds per square inch absolute.

psig: Pounds per square inch gauge (i.e., above atmospheric pressure).

PYOLYSIS: The chemical breaking apart of molecules.

PYROPHORIC: Materials that ignite spontaneously in air below 130 degrees F. Friction can sometimes be the cause of igniting them.


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REACTION: Chemical transformation or change that occurs when two or more substances interact to form new substances.

REACTIVE MATERIAL: Due to shock, pressure, or temperature reactive material is a chemical substance or mixture that will vigorously polymerize, decompose, condense, or become self-reactive.

REACTIVITY: Tendency of a substance to undergo chemical reaction with the release of energy.

REAGENT: Commonly found in most MSDS sheets reagents are substance used in a chemical reaction to detect a substance’s composition or produce another substance.

REDUCING AGENT: Substance or chemical that combines with oxygen or loses electrons to the reaction during a reduction reaction. Reduction reaction always occurs simultaneously.


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SIGNAL WORDS: Distinctive words on a MSDS which serves to alert the reader to the existence and relative degree of a hazard.

SOLUBILITY IN WATER: Percentage of a material (by weight) that will dissolve in water at ambient temperature.

SOLUTION: Composed of a solvent and a dissolved substance, called the solute a solution is a uniformly dispersed mixture.

SOLVENT: Substance that is usually liquid, in which other substances are dissolved. The most common solvent is Water.

SPECIFIC CHEMICAL IDENTITY: Offered in Material Safety Data Sheet information, specific identity is chemical name, CAS number, or other information that reveals the precise chemical designation of the substance.

SPECIFIC GRAVITY: Weight of material compared to equal volume of water.

STABILITY: A material is stable if it remains in the same form under expected and reasonable conditions of storage or use. A material that has the ability to remain in an unchanged state.

SUBLIME: Change from a solid to a vapor phase without passing through the liquid phase.

SYNERGY: Interaction of materials found in Material Safety Data Sheets, to give a combined result different from either material alone.

SYNONYM: Another name or names by which a material is known. Commonly used in MSDS solutions.


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TOXICITY: Sum of adverse effects resulting from exposure to a material.

TRADE NAME: Trademark name or commercial trade name for a material given by the manufacturer.

TRADE SECRET: Any confidential formula pattern, process, device, information, or compilation of information used in an employer’s business and gives the employer an opportunity to obtain an advantage over competitors, which use MSDS services.


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UNSTABLE: Tending toward decomposition or other unwanted chemical change during normal handling or storage.

ug: Microgram, one millionth of a gram.


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VAPOR: Commonly found in MSDS services vapor is a gaseous state of a material suspended in air that would be a liquid or solid under ordinary conditions.

VAPOR DENSITY: Compared to an equal volume of air, vapor density is the weight of vapor or gas; expression of the density of the vapor or gas.

VAPOR PRESSURE: Pressure exerted by a saturated vapor above its liquid.

VAPOR: In a closed container, vapor is a gaseous form of a solid or liquid substance as it evaporates.

VENTILATION: Circulating fresh air to replace contaminated air.

VISCOSITY: Tendency of a fluid to resist internal flow without regard to its density.

VOLATILE ORGANIC COMPOUNDS (VOC): Used in coatings and paint because they evaporate very rapidly.

VOLATILITY: Measure of how quickly a substance forms a vapor at ordinary temperatures.


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