COSHH Glossary

A complete A-Z of COSHH and UK chemical safety terms, abbreviations, and definitions. From ACOP to WEL — everything you need to understand workplace chemical safety regulations.

44 terms defined

A

ACOP: Approved Code of Practice — guidance documents issued by the HSE that give practical advice on how to comply with the law. Following an ACOP is not compulsory, but if you do follow the advice you will be doing enough to comply with the law. The main COSHH ACOP is L5.
ADR: European Agreement concerning the International Carriage of Dangerous Goods by Road. Relevant to transporting hazardous substances under COSHH.
APF: Assigned Protection Factor — a number that indicates the level of respiratory protection that a properly fitted and functioning RPE can provide. For example, an APF of 20 means the RPE reduces exposure by a factor of 20.

B

Biological Agent: Any micro-organism, cell culture, or human endoparasite, including any which have been genetically modified, which may cause infection, allergy, toxicity, or otherwise create a hazard to human health. Covered under COSHH Regulation 2.
Biological Monitoring: The measurement and assessment of hazardous substances or their metabolites in biological specimens (blood, urine, breath) from exposed workers. Used to assess actual internal exposure rather than just airborne levels.

C

Carcinogen: A substance that can cause cancer. Under COSHH, carcinogens require the highest level of control and health surveillance. They are classified as Category 1A or 1B under CLP/GHS.
CAS Number: Chemical Abstracts Service Number — a unique numerical identifier assigned to every chemical substance. Used to unambiguously identify chemicals in COSHH assessments and Safety Data Sheets (e.g., Acetone = 67-64-1).
CLP: Classification, Labelling and Packaging Regulation — the UK regulation that implements the GHS for classifying, labelling, and packaging chemical substances and mixtures. Replaced the old CHIP regulations.
CMR: Carcinogenic, Mutagenic, or toxic to Reproduction — a classification for substances that can cause cancer, genetic mutations, or harm reproductive function. CMR substances require the strictest COSHH controls.
COSHH: Control of Substances Hazardous to Health — UK regulations (COSHH Regulations 2002) requiring employers to assess and control risks from hazardous substances in the workplace. Enforced by the HSE.
COSHH Assessment: A documented evaluation of the health risks from hazardous substances in the workplace, required under Regulation 6 of the COSHH Regulations 2002. Must identify hazards, who is at risk, control measures, and be reviewed regularly.
COSHH Essentials: A free web-based tool from the HSE that helps employers comply with COSHH by producing guidance sheets. It uses a simple risk-banding approach to recommend control measures.
Control Measure: Any measure taken to reduce or eliminate exposure to a hazardous substance. The hierarchy of control is: elimination, substitution, engineering controls, administrative controls, and PPE.

D

DNEL: Derived No-Effect Level — the level of exposure to a substance above which humans should not be exposed. Used in REACH chemical safety assessments.
Dust: Solid particles dispersed in air, generated by mechanical processes like cutting, grinding, or drilling. Common COSHH-relevant dusts include silica, wood, flour, and cement dust.

E

EH40: HSE guidance document "Workplace Exposure Limits" (EH40/2005 with amendments) — the definitive list of UK Workplace Exposure Limits for airborne substances. Contains legally binding WELs for hundreds of substances.
Exposure: Contact with a hazardous substance through inhalation, skin absorption, ingestion, or injection. COSHH assessments must consider all routes of exposure.

F

Fume: Very fine solid particles generated by heating processes such as welding, soldering, or smelting. Welding fume has a WEL of 1 mg/m³ under EH40.

G

GHS: Globally Harmonized System of Classification and Labelling of Chemicals — an international system using 9 standard hazard pictograms (red diamonds) and standardised hazard/precautionary statements to communicate chemical dangers.
GHS Pictogram: One of 9 red diamond-shaped symbols used under GHS to indicate types of chemical hazard: Explosive (GHS01), Flammable (GHS02), Oxidiser (GHS03), Compressed Gas (GHS04), Corrosive (GHS05), Toxic (GHS06), Harmful (GHS07), Health Hazard (GHS08), Environmental (GHS09).

H

H-Statement: Hazard Statement — a standardised phrase (e.g., H301: Toxic if swallowed) describing the nature and severity of a chemical hazard under GHS/CLP. Found on labels and Safety Data Sheets.
HASAWA: Health and Safety at Work etc. Act 1974 — the primary UK legislation covering occupational health and safety. COSHH regulations are made under this Act.
Health Surveillance: Systematic, regular, and appropriate procedures to detect early signs of work-related ill health among employees exposed to certain hazardous substances. Required under COSHH Regulation 11 for substances like isocyanates, silica, and solvents.
HSE: Health and Safety Executive — the UK government agency responsible for enforcing workplace health and safety law, including COSHH regulations. Conducts inspections, issues guidance, and prosecutes non-compliant businesses.
HSG258: HSE guidance document on controlling airborne contaminants at work, specifically relating to Local Exhaust Ventilation (LEV) systems. Covers design, installation, maintenance, and testing of LEV.

I

Inhalable Dust: The fraction of airborne dust that can be breathed in through the nose and mouth. The UK WEL for inhalable dust (not otherwise classified) is 10 mg/m³ (8-hour TWA).
Isocyanate: A group of highly reactive chemicals widely used in paints, varnishes, and polyurethane foams. A leading cause of occupational asthma in the UK. Has very low WELs (0.02 mg/m³ TWA as NCO) and requires health surveillance.

L

LEV: Local Exhaust Ventilation — an engineering control that captures airborne contaminants (dust, fumes, vapours) at or near the source before they spread into the workplace. Must be tested at least every 14 months under COSHH Regulation 9.
LTEL: Long-Term Exposure Limit — another name for the 8-hour TWA workplace exposure limit. The maximum average concentration of a substance over a normal 8-hour working day.

M

MSDS: Material Safety Data Sheet — the previous name for a Safety Data Sheet (SDS). The term SDS is now standard under GHS/CLP, though MSDS is still widely used.
Mutagen: A substance that can cause heritable genetic mutations. Mutagens are classified as CMR substances and require the highest level of COSHH control.

O

OEL: Occupational Exposure Limit — a generic term for the maximum allowable concentration of a substance in workplace air. In the UK, the specific term is Workplace Exposure Limit (WEL).

P

P-Statement: Precautionary Statement — a standardised phrase (e.g., P261: Avoid breathing dust/fume) describing recommended measures to prevent or reduce adverse effects from chemical exposure. Found on labels and SDS.
PPE: Personal Protective Equipment — equipment worn to minimise exposure to hazards. Under COSHH, PPE is the last resort in the hierarchy of control. Includes gloves, goggles, respirators, and protective clothing.

R

REACH: Registration, Evaluation, Authorisation and Restriction of Chemicals — a broad UK/EU regulatory framework governing the manufacture, import, and supply of chemicals. UK REACH replaced EU REACH after Brexit for the GB market.
Respirable Dust: The fraction of airborne dust small enough to penetrate deep into the lungs (alveoli). The UK WEL for respirable dust (not otherwise classified) is 4 mg/m³ (8-hour TWA). Silica dust has a much lower WEL of 0.1 mg/m³.
RPE: Respiratory Protective Equipment — a subset of PPE specifically designed to protect the wearer from inhaling hazardous substances. Includes disposable masks, half-face respirators, and powered air-purifying respirators. Must be face-fit tested.

S

SDS: Safety Data Sheet — a 16-section document provided by chemical manufacturers/suppliers containing hazard identification, composition, first-aid measures, handling, exposure controls, and disposal information. Essential for completing COSHH assessments.
Sensitiser: A substance that can cause an allergic reaction (sensitisation) after repeated exposure. Respiratory sensitisers (e.g., isocyanates, flour dust) can cause occupational asthma. Skin sensitisers (e.g., chromium, epoxy resin) can cause allergic contact dermatitis.
Silica Dust: Respirable crystalline silica (RCS) dust, generated when cutting, drilling, or grinding materials like concrete, brick, and stone. Has a UK WEL of 0.1 mg/m³. A major cause of silicosis, lung cancer, and COPD in construction workers.
STEL: Short-Term Exposure Limit — the maximum concentration of a substance averaged over a 15-minute reference period. Workers must not be exposed above the STEL, even if the 8-hour TWA is within limits.
Substitution: Replacing a hazardous substance with a less hazardous alternative. The second level in the hierarchy of control (after elimination) and a key COSHH principle.

T

TWA: Time-Weighted Average — the average concentration of a substance in air over a specified time period (usually 8 hours for WELs). Calculated by measuring exposure levels throughout a shift and averaging them.

W

WEL: Workplace Exposure Limit — the maximum concentration of an airborne substance averaged over a reference period (8-hour TWA or 15-minute STEL) to which workers may be exposed. Published in EH40 and legally binding in the UK.

Related Resources

What is COSHH? — Complete UK Guide Workplace Exposure Limits (WELs) Explained Free GHS Hazard Symbol Lookup The 8 Steps of a COSHH Assessment COSHH Risk Assessment Software COSHH Guidance by Industry

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