Workplace Exposure Limits (WEL) Lookup
Search UK Workplace Exposure Limits from HSE's EH40. Find the 8-hour TWA and 15-minute STEL for common hazardous substances.
Source: HSE EH40/2005 (Fourth edition, 2020). Always check the latest EH40 for current values.
Showing 25 of 25 substances
| Substance | CAS No. | 8-hr TWA | 15-min STEL | Notes |
|---|---|---|---|---|
| Acetone | 67-64-1 | 500 ppm (1210 mg/m³) | 1500 ppm (3620 mg/m³) | Common solvent. Flammable. |
| Ammonia | 7664-41-7 | 25 ppm (18 mg/m³) | 35 ppm (25 mg/m³) | Pungent gas. Common in cleaning and refrigeration. |
| Benzene | 71-43-2 | 1 ppm (3.25 mg/m³) | — | Carcinogen (Category 1). Health surveillance required. |
| Carbon dioxide | 124-38-9 | 5000 ppm (9150 mg/m³) | 15000 ppm (27400 mg/m³) | Asphyxiant at high concentrations. |
| Carbon monoxide | 630-08-0 | 20 ppm (23 mg/m³) | 100 ppm (117 mg/m³) | Odourless. Vehicle exhaust, combustion. |
| Chlorine | 7782-50-5 | 0.5 ppm (1.5 mg/m³) | 1 ppm (3 mg/m³) | Toxic. Released when bleach mixed with acids. |
| Ethanol | 64-17-5 | 1000 ppm (1920 mg/m³) | — | Common solvent and sanitiser base. |
| Flour dust | — | 10 mg/m³ (inhalable) | 30 mg/m³ (inhalable) | Respiratory sensitiser. Can cause occupational asthma. Health surveillance required. |
| Formaldehyde | 50-00-0 | 2 ppm (2.5 mg/m³) | 2 ppm (2.5 mg/m³) | Carcinogen. Used in some keratin treatments and resins. |
| Glutaraldehyde | 111-30-8 | 0.05 ppm (0.2 mg/m³) | 0.05 ppm (0.2 mg/m³) | Respiratory sensitiser. Used in disinfection. |
| Hardwood dust | — | 3 mg/m³ (inhalable) | — | Carcinogen (nasal cancer). Health surveillance required. 40-year record retention. |
| Hydrogen chloride | 7647-01-0 | 1 ppm (2 mg/m³) | 5 ppm (8 mg/m³) | Corrosive. Found in acidic cleaners. |
| Isocyanates (as NCO) | Various | 0.02 mg/m³ | 0.07 mg/m³ | Potent respiratory sensitiser. Paints, foams, adhesives. Health surveillance required. |
| Isopropanol | 67-63-0 | 400 ppm (999 mg/m³) | 500 ppm (1250 mg/m³) | Common solvent and sanitiser. |
| Lead (inorganic) | 7439-92-1 | 0.15 mg/m³ | — | Toxic metal. Health surveillance and blood monitoring required above action level. |
| Methanol | 67-56-1 | 200 ppm (266 mg/m³) | 250 ppm (333 mg/m³) | Toxic. Skin absorption. Used in degreasers and fuels. |
| Nitrogen dioxide | 10102-44-0 | 0.5 ppm (0.96 mg/m³) | 1 ppm (1.91 mg/m³) | Found in vehicle exhaust and welding fume. |
| Silica dust (respirable crystalline) | 14808-60-7 | 0.1 mg/m³ (respirable) | — | Causes silicosis. Construction, stone cutting. Health surveillance required. |
| Softwood dust | — | 5 mg/m³ (inhalable) | — | Respiratory sensitiser. Health surveillance recommended. |
| Styrene | 100-42-5 | 100 ppm (430 mg/m³) | 250 ppm (1080 mg/m³) | Used in GRP/fibreglass work. |
| Toluene | 108-88-3 | 50 ppm (191 mg/m³) | 100 ppm (384 mg/m³) | Common solvent. Skin absorption. |
| Trichloroethylene | 79-01-6 | 100 ppm (550 mg/m³) | 150 ppm (820 mg/m³) | Degreasing solvent. Carcinogen. |
| Welding fume (total inhalable) | — | 5 mg/m³ | — | Carcinogen (IARC Group 1). LEV or RPE required for all welding. Health surveillance required. |
| White spirit | 8052-41-3 | 25 ppm | — | Solvent. Paint thinning, degreasing. |
| Xylene (mixed isomers) | 1330-20-7 | 50 ppm (220 mg/m³) | 100 ppm (441 mg/m³) | Solvent in paints and adhesives. Skin absorption. |
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Related resources
This table provides a summary of selected WELs from EH40. It is not exhaustive. Values may be updated by HSE — always refer to the current edition of EH40 for definitive limits. This does not constitute professional occupational hygiene advice.