COSHH & Hazardous Substances

What COSHH Requires

Control of Substances Hazardous to Health Regulations 2002 (COSHH). Applies to chemicals, dusts, fumes, vapours, mists, gases, and biological agents.

Employers must assess the risk from hazardous substances and put in place adequate controls before work begins.

Worker duty (Reg 8): use control equipment and PPE as instructed; report any defects in control equipment or PPE to a supervisor.

Hierarchy of Control (Reg 7) — Priority Order

Controls must be applied in priority order — work down the hierarchy only when a higher-level control is not reasonably practicable:

1. Eliminate — remove the substance or process entirely
2. Substitute — replace with a less hazardous substance or process
3. Engineering controls — enclose the process, use Local Exhaust Ventilation (LEV)
4. Administrative / ways of working — reduce exposure duration, job rotation, safe systems of work
5. PPE — last resort; must not be the sole control unless it is genuinely the only option

PPE protects only the wearer, it can fail, and it must always be used alongside higher-level controls where possible.

Workplace Exposure Limits (WELs) — EH40/2005

A WEL is the maximum airborne concentration of a hazardous substance a worker may be exposed to. Two time periods: 8-hour TWA (Time Weighted Average) and 15-minute STEL (Short-Term Exposure Limit). Units: mg/m³ or ppm.

For carcinogens, mutagens, and asthmagens, exposure must be reduced As Low As Reasonably Practicable (ALARP) below the WEL — there is no safe level for these substances.

Safety Data Sheets (SDS)

16-section document required for every hazardous chemical. Key sections: §2 hazard identification and CLP classification; §8 exposure controls and PPE requirements (includes the WEL).

Workers should check the SDS before using any unfamiliar chemical. Your employer must make the SDS available to you.

GHS/CLP Hazard Pictograms (GB CLP — red-bordered white diamond, black symbol)

• GHS01 — Exploding bomb → Explosive
• GHS02 — Flame → Flammable
• GHS03 — Flame over circle → Oxidising
• GHS04 — Gas cylinder → Gas under pressure
• GHS05 — Corrosion → Corrosive (skin / eye / metal)
• GHS06 — Skull & crossbones → Acute toxicity (fatal / toxic)
• GHS07 — Exclamation mark → Irritant / harmful / sensitiser
• GHS08 — Health hazard (starburst torso) → Serious health hazard (CMR, STOT, aspiration)
• GHS09 — Environment (tree & fish) → Hazardous to aquatic environment

GHS replaced the old orange-and-black CHIP symbols. If in doubt, consult the Safety Data Sheet (SDS). Source: https://www.hse.gov.uk/chemical-classification/labelling-packaging/hazard-symbols-hazard-pictograms.htm