SDS and Chemical Safety Glossary

This glossary defines 162 terms you will meet on safety data sheets, chemical labels and in workplace chemical safety programs. Each entry starts with a one-sentence definition, explains it in plain English and shows where it appears on the 16-section SDS.

Definitions are general reference. Always follow the current SDS from your supplier and the rules that apply to your workplace.

A

ACGIH: The American Conference of Governmental Industrial Hygienists, a professional body that publishes TLV exposure guidelines.
Action level: An exposure level, usually a fraction of the PEL, at which an employer must start monitoring or medical surveillance.
Acute toxicity: Harmful effects that appear shortly after a single exposure or several exposures within a day, by mouth, skin or inhalation.
Aquatic toxicity: The harm a chemical can cause to fish, water fleas, algae and other organisms living in water, as acute or chronic effects.
Article: A manufactured item whose shape or design matters more than its chemistry and that releases no hazardous chemical under normal use.
Asphyxiant: A gas that harms by displacing oxygen from the air or by preventing the body from using oxygen.
Aspiration hazard: The danger that a liquid or solid enters the lungs after swallowing or vomiting, causing severe injury even from a small amount.
Assigned protection factor (APF): The APF is the level of workplace protection a class of respirator is expected to provide when used within a complete program.
Autoignition temperature: The temperature at which a material ignites on its own in air, with no spark or flame needed.

B

Bioaccumulation: The build-up of a chemical in a living organism over time, faster than the body can break it down or excrete it.
Bioconcentration factor (BCF): The ratio of a chemical's concentration in an organism, usually fish, to its concentration in the surrounding water.
Biodegradability: The extent to which microorganisms can break a chemical down into simple natural substances such as carbon dioxide and water.
Biological exposure index (BEI): An ACGIH guidance value for a chemical or its metabolite in blood, urine or breath that reflects total worker uptake.
Boiling point: The temperature at which a liquid's vapor pressure equals the surrounding pressure and it boils; low values signal volatility.
Breakthrough time: Breakthrough time is how long a chemical takes to pass through a glove or protective fabric and be detectable on the inside.
Bulk container: A bulk container is a large package or vessel, such as a tank, tote or large drum, used to store or move large quantities of material.

C

Carcinogen: A substance or mixture that can cause cancer or increase its incidence after exposure, often years later.
CAS Registry Number: A unique numeric identifier assigned by the Chemical Abstracts Service to a specific chemical substance, written in three hyphen-separated parts.
Ceiling limit: An airborne concentration that must not be exceeded at any time during the workday, not even briefly.
CERCLA: The US law that governs cleanup of contaminated sites and requires reporting of hazardous substance releases above set amounts.
Chemical fume hood: A chemical fume hood is a ventilated enclosure that draws vapors and fumes away from the user and exhausts them outside.
Chemical segregation: Chemical segregation means storing incompatible chemicals apart so that a leak or fire cannot cause them to react dangerously.
Chemical splash goggles: Chemical splash goggles are sealed eye protection that keeps liquid splashes, mists and droplets away from the eyes.
Chemical stability: How well a chemical keeps its composition and properties over time under normal storage and handling conditions.
Chemical-resistant gloves: Chemical-resistant gloves are made from materials chosen to resist a specific chemical so it does not reach the skin through the glove.
CHEMTREC: CHEMTREC is a 24-hour emergency information service that gives responders chemical hazard advice during transport and other incidents.
Chronic toxicity: Harmful effects that develop from repeated or long-term exposure, often at levels that cause no immediate symptoms.
CLP Regulation: The European Union regulation that applies the GHS to classify, label and package chemical substances and mixtures.
Combustible liquid: A liquid that gives off ignitable vapor only when heated above ordinary room conditions; less volatile than a flammable liquid.
Compressed gas: A gas held in a cylinder or tank under pressure, which carries a risk of rupture and rocket-like release even if the gas itself is harmless.
Confined space: A confined space is an area large enough to enter but with limited entry and exit, not designed for continuous occupancy, and often hazardous.
Corrosive: A substance that destroys living tissue on contact, and in many cases also attacks metals, causing burns and serious eye damage.
Corrosive to metals: A GHS physical hazard for chemicals that can damage or destroy metal, separate from the skin and eye corrosion class.
Cryogenic liquid: A gas cooled to a very low temperature so it exists as a liquid, such as liquid nitrogen, causing cold burns and rapid expansion.

D

Decontamination: Decontamination is the process of removing or neutralizing hazardous chemicals from people, equipment and surfaces after exposure.
Dermal exposure: Contact of a chemical with the skin, which can cause local injury or let the substance be absorbed into the body.
DNEL: Derived No-Effect Level: an exposure level for humans below which no adverse effect is expected, set under REACH.
DOT hazard class: The DOT hazard class is the category a hazardous material falls into for transport, such as flammable liquids or corrosives.
Drum: A drum is a cylindrical container, made of steel, plastic or fiber, used to store and ship liquids and solids in moderate quantities.

E

EC number: A seven-digit European Community number that identifies substances on EU inventories, used in REACH and CLP documents.
EC50: The concentration of a chemical that causes a defined effect, such as immobility or reduced growth, in half of a test population.
Emergency response: Emergency response is the planned set of actions taken to protect people and limit damage when a chemical release, fire or exposure occurs.
Emergency Response Guidebook (ERG): The ERG is the North American guidebook that first responders use to identify a transported hazardous material and act safely in the first minutes.
Engineering controls: Engineering controls are physical changes to equipment, process or workplace that reduce exposure at the source without relying on worker behavior.
EPCRA: A US law that requires emergency planning, chemical release reporting and public access to chemical inventory information.
Evaporation rate: How fast a liquid turns to vapor compared with a reference solvent; fast evaporators raise vapor exposure and fire risk quickly.
Explosive: A substance or article that can react chemically to produce gas at such speed and pressure that it damages its surroundings.
Eyewash station (ANSI Z358.1): An eyewash station delivers a gentle, continuous flow of tepid water to flush chemicals from the eyes, and must be able to keep flowing for at least 15 minutes.

F

First responder: A first responder is a person trained to be among the first on the scene of a chemical incident to protect people and call for help.
Flammable gas: A gas that can ignite and burn when mixed with air in the right proportions, such as hydrogen, propane or acetylene.
Flammable liquid: A liquid with a low flash point that gives off enough vapor at or near room temperature to ignite.
Flammable range: The span of vapor-in-air concentrations, from the LEL up to the UEL, in which a mixture can ignite or explode.
Flammable solid: A solid that ignites easily from brief contact with an ignition source and burns quickly, or may cause fire by friction.
Flammable storage cabinet: A flammable storage cabinet is a fire-resistant, double-walled cabinet designed to hold flammable liquids safely in the workplace.
Flash point: The lowest temperature at which a liquid gives off enough vapor to ignite briefly when an ignition source is present.

G

Globally Harmonized System (GHS): The UN system that sets common criteria for classifying chemical hazards and standard labels and safety data sheets worldwide.
Grounding and bonding: Grounding and bonding connect containers to each other and to earth to prevent static electricity sparks when flammable liquids are transferred.

H

Hazard category: A numbered subdivision of a hazard class that shows severity, where Category 1 is generally the most severe.
Hazard class: A broad type of physical, health, or environmental hazard in GHS, such as flammable liquids, skin corrosion, or acute toxicity.
Hazard Communication Standard (HazCom): OSHA's rule (29 CFR 1910.1200) requiring chemical labeling, safety data sheets, a written program, and worker training.
Hazard not otherwise classified (HNOC): A hazard that is not covered by a GHS hazard class in OSHA's HazCom standard but must still be communicated on the SDS.
Hazard statement: A standardized phrase with an H-code that describes the nature and degree of a chemical's hazard, such as 'Causes serious eye damage'.
Hazardous decomposition products: Harmful substances that form when a chemical breaks down from heat, fire or reaction, such as toxic gases or irritating fumes.
Hazardous polymerization: An uncontrolled reaction in which molecules link together rapidly, releasing heat and pressure that can rupture containers.
Hazardous waste: Discarded material that is dangerous to health or the environment because it is listed by regulators or shows a hazardous characteristic.
HazCom training: Employee training required by OSHA's Hazard Communication standard so workers can understand chemical hazards and use labels and SDSs.
Hierarchy of controls: The hierarchy of controls ranks ways to reduce a hazard, from removing it entirely to relying on personal protective equipment.
HMIS: A workplace labeling system that rates health, flammability, physical hazard and protective equipment on a 0 to 4 color-bar label.

I

IARC: The International Agency for Research on Cancer, part of the WHO, which classifies agents by the strength of evidence that they cause cancer.
IBC tote: An IBC tote is an intermediate bulk container, usually a plastic tank in a metal cage on a pallet, holding hundreds of liters of liquid.
Immediately dangerous to life or health (IDLH): An atmosphere that could cause death, serious lasting harm or prevent escape; NIOSH publishes IDLH values used in respirator choice.
Incompatible materials: Substances that must not contact or mix with a chemical because they can cause fire, toxic gas, heat or violent reaction.
Ingestion: Swallowing a chemical, whether directly or through contaminated hands, food, drink or surfaces.
Inhalation exposure: Breathing in a chemical as a gas, vapor, dust, mist or fume, the most common way workplace chemicals enter the body.
Irritant: A substance that causes reversible inflammation of skin, eyes or airways on contact, short of the permanent damage caused by a corrosive.

L

LC50: The concentration of a chemical in air or water that is expected to kill half of a group of test animals over a set time.
LD50: The single dose of a substance, given orally or on skin, that is expected to kill half of a group of test animals.
Limited quantity: Limited quantity is a transport exception allowing small amounts of some hazardous materials to ship with reduced packaging and marking.
LOAEL: The lowest dose or exposure level in a study at which a harmful effect was observed in the test group.
Local exhaust ventilation (LEV): Local exhaust ventilation captures fumes, vapors or dust right where they are made and carries them away from the worker's breathing zone.
LogKow (octanol-water partition coefficient): A number showing how a chemical divides between oil-like octanol and water, used to estimate its tendency to accumulate in organisms.
Lower explosive limit (LEL): The lowest concentration of a vapor or gas in air that can ignite; below it the mixture is too lean to burn.

M

Marine pollutant: A substance regulated for transport because it is especially harmful to the sea and marine life, marked with a special symbol.
Material Safety Data Sheet (MSDS): The older name for a safety data sheet, used before GHS alignment; formats varied and the term is now obsolete in most regulations.
Melting point: The temperature at which a solid turns to liquid; it also marks the freezing point and helps predict storage and handling.
Mixture: A combination of two or more substances that do not react with each other, such as most paints, cleaners, and fuels.
Mutagen: A substance that causes permanent changes to DNA in cells, with concern that changes in germ cells could be inherited.

N

NA number: A four-digit identification number prefixed NA, used in North American transport for materials without a UN number or with a domestic-only description.
Narcotic effects: Central nervous system depression from chemical exposure, causing drowsiness, dizziness, confusion or loss of consciousness.
National Toxicology Program (NTP): A US federal interagency program that tests chemicals for toxicity and publishes the Report on Carcinogens.
Neutralization: Neutralization is the reaction of an acid with a base to form a less hazardous, closer-to-neutral solution, often used in spill response.
NFPA 704: A standard from the National Fire Protection Association that rates health, flammability and instability hazards from 0 to 4 in a diamond sign.
NIOSH: The National Institute for Occupational Safety and Health, a US research agency that recommends exposure limits and approves respirators.
NIOSH approval (respirators): NIOSH approval means a respirator has been tested and certified to meet the federal requirements under 42 CFR Part 84.
NOAEL: The highest dose or exposure level in a study at which no harmful effect was seen in the test group.

O

Occupational exposure limit (OEL): A general term for any limit on workplace exposure to a chemical, including PELs, RELs, TLVs and company limits.
Odor threshold: The lowest concentration in air at which most people can smell a chemical; it is a poor safeguard against overexposure.
Organic peroxide: An organic compound with an oxygen-oxygen bond that can burn fiercely, decompose violently or detonate with heat or contamination.
OSHA: The US Occupational Safety and Health Administration, the federal agency that sets and enforces workplace safety standards.
Oxidizer: A chemical that gives up oxygen or otherwise helps other materials burn harder, even though it may not burn itself.

P

Packing group: A packing group (I, II or III) shows how dangerous a hazardous material is within its class and sets the packaging strength needed.
Parts per million (ppm): A concentration unit used for gases and vapors in air; one ppm is one part of the chemical per million parts of air.
PBT and vPvB: Substances that are persistent, bioaccumulative and toxic (PBT), or very persistent and very bioaccumulative (vPvB).
Permeation: Permeation is the movement of a chemical through protective material at the molecular level, even when the material has no holes.
Permissible exposure limit (PEL): An OSHA legal limit on the airborne concentration of a substance that workers may be exposed to.
Peroxide former: A chemical, often an ether, that slowly forms explosive peroxides on exposure to air during storage.
Persistence (environmental): How long a chemical stays in the environment before it breaks down by natural processes such as microbes, light or water.
Personal protective equipment (PPE): PPE is equipment worn to protect the body from chemical, physical or biological hazards, used when other controls cannot remove the risk.
pH: A logarithmic 0 to 14 scale showing how acidic or alkaline a water-based material is; 7 is neutral.
Pictogram: A red-bordered diamond symbol on a GHS label that shows the type of hazard at a glance, such as a flame or skull.
Placard: A placard is a large diamond-shaped sign on a vehicle or container that shows the hazard class of the dangerous goods inside.
PNEC: Predicted No-Effect Concentration: the level of a chemical in an environmental compartment below which harm to organisms is not expected.
Poison control center: A free, 24-hour service staffed by trained specialists who advise on treating poisonings and chemical exposures.
Precautionary statement: A standardized P-coded phrase on a GHS label that says how to prevent, respond to, store, or dispose of a hazardous chemical.
Product identifier: The name or number used for a hazardous product on its label and SDS, such as a brand name, chemical name, or code.
Proper shipping name: The proper shipping name is the official wording from the hazmat table that must be used to describe a dangerous good on shipping papers.
Proposition 65: California's law requiring warnings about exposure to chemicals listed as causing cancer or reproductive harm.
Pyrophoric: A liquid, solid or gas that can ignite on its own in air, without any spark or flame, usually within moments.

R

RCRA: The US law that regulates hazardous waste from generation through transport, treatment, storage and disposal.
REACH registration: The EU process requiring companies to register chemical substances with the European Chemicals Agency and supply safety data.
Recommended exposure limit (REL): A NIOSH-recommended occupational exposure limit; advisory only, but often more protective than the OSHA PEL.
Relative density: The density of a substance divided by the density of a reference, usually water; the GHS-aligned term for specific gravity.
Reportable quantity (RQ): The amount of a hazardous substance that, if released in a 24-hour period, must be reported to the National Response Center.
Reproductive toxicant: A substance that can harm sexual function, fertility, or the development of offspring, including effects through lactation.
Respirator: A respirator is a device worn over the face that filters contaminated air or supplies clean air to protect the wearer's lungs.
Respirator fit test: A respirator fit test checks that a specific tight-fitting facepiece seals properly to a specific person's face.
Routes of exposure: The ways a chemical can enter the body: inhalation, skin or eye contact, ingestion, and injection.

S

Safety Data Sheet (SDS): A standardized 16-section document from the supplier describing a chemical's hazards, safe handling, storage, and emergency measures.
Safety shower: A safety shower is emergency equipment that drenches the whole body with water to wash off chemicals quickly.
SCBA: SCBA, or self-contained breathing apparatus, gives the wearer a portable supply of clean air for atmospheres that are dangerous to breathe.
SDS binder: An SDS binder is the workplace collection of safety data sheets, kept where workers can read them during every shift.
Secondary container label: A secondary container label identifies the contents and hazards of a chemical that has been poured into a smaller or different container.
Secondary containment: Secondary containment is a second barrier, such as a tray or bund, that catches leaks from a primary chemical container.
Self-reactive substance: A thermally unstable liquid or solid that can decompose strongly without oxygen, and so can burn or explode on its own.
Sensitizer: A substance that can trigger an allergic reaction of the skin or airways after repeated exposure, often at very low levels.
Short-term exposure limit (STEL): A 15-minute average exposure limit that should not be exceeded, even if the 8-hour average is within limits.
Signal word: The single word on a GHS label, either Danger or Warning, that shows how severe the product's hazard is.
Skin notation: A flag next to an exposure limit warning that the chemical can be absorbed through the skin, adding to total dose.
Solubility in water: How much of a substance dissolves in water; it affects spill cleanup, exposure routes and environmental fate.
Specific gravity: The density of a liquid or solid compared with water (water = 1); it shows whether a material floats or sinks.
Spill kit: A spill kit is a ready-to-use set of absorbents, PPE and disposal supplies for cleaning up a chemical spill safely.
Substance: A chemical element or compound in its natural state or produced by a process, including any additives needed to keep it stable.
Substance of Very High Concern (SVHC): A chemical identified under EU REACH as having serious, long-term hazards, such as cancer or persistence, and subject to extra controls.
Synonym (chemical name): An alternate name for the same chemical, such as a common, trade, or older systematic name, listed to help you match products and records.

T

Target organ: The organ or body system a chemical mainly harms, such as liver, kidneys, nervous system or lungs.
Teratogen: A substance that can interfere with normal development of an embryo or fetus and cause birth defects.
Threshold limit value (TLV): An ACGIH guideline for airborne exposure believed to be safe for nearly all workers day after day; not a legal limit in the US.
Threshold Planning Quantity (TPQ): The amount of an extremely hazardous substance on site that triggers emergency planning notification under EPCRA.
Tier II report: An annual inventory of hazardous chemicals stored at a facility, filed under EPCRA section 312 for emergency planners and responders.
Time-weighted average (TWA): An exposure averaged over a work shift, typically 8 hours, which lets short peaks balance against low periods.
Toxics Release Inventory (TRI): A US program under EPCRA section 313 requiring covered facilities to report annual releases and waste management of listed chemicals.
Trade secret (confidential business information): A formula or ingredient identity a supplier may withhold from an SDS, with strict conditions and exceptions for medical emergencies.
TSCA: The US law, administered by the EPA, that regulates the manufacture, import, use and disposal of industrial chemicals.

U

UN number: A four-digit code assigned under United Nations transport recommendations that identifies a hazardous substance or group of substances in shipping.
Upper explosive limit (UEL): The highest concentration of a vapor or gas in air that can still ignite; above it the mixture is too rich to burn.

V

Vapor density: How heavy a gas or vapor is compared with air (air = 1); values above 1 mean the vapor sinks and collects low.
Vapor pressure: A measure of how readily a liquid or solid evaporates; higher vapor pressure means more vapor in the air at a given temperature.
Viscosity: A liquid's resistance to flow; thin liquids spread fast, thick ones are slow to pour, spill or drain.
Volatile organic compound (VOC): A carbon-containing chemical that evaporates easily at room temperature and is often regulated for air quality and workplace reasons.

W

Water-reactive: A substance that reacts with water or moisture to release flammable gas, heat or other hazardous products.
WHMIS: Canada's national system for communicating chemical hazards at work through labels, safety data sheets and worker training.
Workplace label: A workplace label is the in-house label an employer applies to chemical containers so workers can identify the contents and hazards.

Looking for a specific chemical? Browse the chemical SDS index, the GHS reference, DOT hazard classes or the NFPA 704 diamond.