Solvent Compliance

Compliance & Guidance · Compliance & Guidance overview

Solvent compliance in the UK is governed primarily by the Control of Substances Hazardous to Health Regulations 2002 (COSHH). Employers who use, generate or handle solvent vapours must assess risks, prevent or control exposure, monitor where Workplace Exposure Limits apply, and maintain records of the assessment and control measures.

The COSHH framework for solvent management

COSHH applies to any substance hazardous to health, including all organic solvents with a Workplace Exposure Limit listed in HSE EH40, solvents classified as irritants, sensitisers, carcinogens or reproductive toxins, and solvent mixtures that create a health risk. The employer's duties include risk assessment, prevention or control of exposure, use of suitable controls, maintenance and testing of control equipment, health surveillance where appropriate, information and training for employees, and emergency planning.

The key principle is that exposure should be prevented where reasonably practicable. Where prevention is not reasonably practicable, exposure must be adequately controlled. 'Adequate control' for substances with a WEL means reducing exposure so far as is reasonably practicable and, in any case, below the WEL.

Workplace Exposure Limits in HSE EH40

HSE EH40 publishes Workplace Exposure Limits for approximately 500 substances. Limits are expressed as 8-hour time-weighted averages (TWA) and, for substances with acute effects, 15-minute short-term exposure limits (STEL). The WEL is the maximum concentration to which workers may be exposed, averaged over the reference period.

Common solvents with published WELs include toluene (50 ppm 8-hr TWA), xylene (50 ppm 8-hr TWA), styrene (100 ppm 8-hr TWA), acetone (500 ppm 8-hr TWA), n-hexane (20 ppm 8-hr TWA), and benzene (1 ppm 8-hr TWA). Formaldehyde has a 2 ppm 15-minute STEL. Isocyanates are assigned a ceiling limit of 0.02 mg/m³ (as NCO) for total isocyanate, with additional specific limits for individual compounds.

WELs are revised periodically as new toxicological evidence emerges. Employers should ensure they are working with the current edition of EH40, available from the Health and Safety Executive website.

Toluene: 50 ppm 8-hr TWA / 100 ppm 15-min STEL
Xylene (mixed isomers): 50 ppm 8-hr TWA / 100 ppm 15-min STEL
Styrene: 100 ppm 8-hr TWA / 250 ppm 15-min STEL
Acetone: 500 ppm 8-hr TWA / 1500 ppm 15-min STEL
n-Hexane: 20 ppm 8-hr TWA / 60 ppm 15-min STEL
Benzene: 1 ppm 8-hr TWA (carcinogen, as low as reasonably practicable)
Formaldehyde: 2 ppm 15-min STEL
Total isocyanate: 0.02 mg/m³ (as NCO) ceiling

Exposure assessment and air monitoring obligations

COSHH requires exposure assessment where a substance hazardous to health is used or generated. Where a WEL exists, air monitoring is the standard method for demonstrating compliance. The assessment must be suitable and sufficient, meaning it should identify the substances, estimate or measure exposure, evaluate control adequacy, and record findings.

Monitoring must be carried out by a competent person, typically an occupational hygienist, using validated methods. Personal pumped sampling for 8-hour TWA assessment is the norm for routine compliance. Task-based sampling captures short-term peaks. Direct-reading instruments supplement formal sampling for screening, LEV verification and incident investigation.

Records of exposure assessments and monitoring results must be kept for at least 40 years for substances assigned a notation of carcinogenic, mutagenic or toxic to reproduction (CMR substances). For other substances, a retention period of at least five years from the date of the record is good practice.

Hierarchy of solvent control

COSHH mandates a hierarchy of control. The first option is to eliminate the hazardous substance by changing the process, product or material. Substitution with a less hazardous solvent, water-based formulation or solvent-free alternative is the next preferred option. Many industries have successfully replaced solvent-based coatings, adhesives and degreasers with safer alternatives.

Where solvents cannot be eliminated or substituted, engineering controls must be applied. Enclosure of the process, local exhaust ventilation, automated application and isolation of the operator from the emission source all reduce exposure. Controls must be maintained, examined and tested regularly. LEV systems require thorough examination and testing at least every 14 months under COSHH.

Administrative controls, including restricted zones, job rotation, time limits and standard operating procedures, reduce exposure but do not replace engineering controls. Respiratory protective equipment is acceptable only where exposure cannot be reduced sufficiently by other means. RPE must be suitable for the substance, properly fitted, maintained and stored, and users must be trained and fit-tested.

Documentation, training and review

The COSHH assessment must be documented in writing unless the employer has five or fewer employees, in which case it need not be written but must still be suitable and sufficient. The assessment should identify the substance, the work activity, the exposure potential, the controls in place, any health surveillance requirements, and the person responsible for review.

Employees must be informed of the risks, the control measures, and the correct use of any RPE or PPE. Training should be practical, specific to the tasks performed, and refreshed when processes, substances or controls change. Supervisors should verify that controls are being used correctly on a routine basis.

COSHH assessments must be reviewed regularly and whenever there is reason to suspect they are no longer valid. Triggers for review include changes to the substance, process or controls; new toxicological evidence; results of exposure monitoring or health surveillance; and incidents or near-misses involving solvent exposure.

Frequently asked questions

What is the difference between a WEL and an OEL?

WEL (Workplace Exposure Limit) is the UK term used in COSHH and published in HSE EH40. OEL (Occupational Exposure Limit) is a broader term used internationally. In the UK context, WEL is the correct and legally relevant term.

Do all solvents have a WEL?

No. HSE EH40 lists WELs for approximately 500 substances. Solvents without a published WEL must still be controlled under COSHH. The employer must ensure exposure is prevented or, where not reasonably practicable, adequately controlled based on available toxicological data.

How often must LEV be thoroughly examined?

Under COSHH, local exhaust ventilation systems must be thoroughly examined and tested at least every 14 months by a competent person. More frequent examination may be required for high-risk processes or where the system is known to deteriorate rapidly.

Is air monitoring mandatory for all solvent processes?

Monitoring is required where there is a WEL and uncertainty about whether exposure is adequately controlled. It is not necessarily mandatory for every process, but employers must have a reasonable basis for concluding that exposure is controlled. Where there is doubt, monitoring should be conducted.

What records must be kept under COSHH?

Employers must keep records of the risk assessment, control measures, examination and test results for LEV, air monitoring results, and health surveillance records (where required). CMR substance records must be kept for 40 years. Other records should be retained for at least five years.

Who can carry out a COSHH assessment?

The assessor must be competent, meaning they have sufficient training, experience and knowledge of the substances, processes and controls. For complex solvent processes or substances with low WELs, involvement of an occupational hygienist is advisable to ensure the assessment is suitable and sufficient.