Guide · Employer duty of care

UK workplace heat — what HSE actually requires of employers.

A fact-checked summary of employer duties under the Workplace Regulations 1992, HSE thermal comfort guidance and CIBSE overheating benchmarks.

Hot British office during a heatwave with sunlight streaming through blinds onto empty desks
In short

UK law sets no legal maximum workplace temperature, but under the Workplace (Health, Safety and Welfare) Regulations 1992 employers must maintain a 'reasonable' temperature. HSE guidance requires a thermal comfort risk assessment. CIBSE TM52 uses 25 °C as the operative-temperature benchmark for non-domestic occupied spaces; above 28 °C, action is expected.

Employer duties

Four duties the HSE will expect you to evidence.

  • Provide a 'reasonable' temperature

    Regulation 7 of the Workplace (Health, Safety and Welfare) Regulations 1992 requires employers to keep indoor workplaces at a reasonable temperature. The Approved Code of Practice sets a minimum of 16 °C (13 °C for physical work) but does not set an upper legal limit — 'reasonable' has to be judged against activity, clothing, humidity and airflow.

  • Assess thermal comfort risk

    HSE guidance on thermal comfort lists six factors: air temperature, radiant temperature, humidity, air velocity, clothing and work rate. During heatwaves employers should carry out a documented thermal comfort risk assessment covering all six, not just the thermometer reading.

  • Consult employees

    HSE guidance and the Safety Representatives and Safety Committees Regulations require consultation with workers or union safety reps on temperature and comfort. A working thermometer available to staff is a documented HSE expectation.

  • Protect vulnerable workers

    Pregnant workers, workers with medical conditions, older workers and those on medications that affect thermoregulation need individual risk consideration. The HSE explicitly calls this out under the Management of Health and Safety at Work Regulations 1999.

Hierarchy of controls

Engineering > administrative > personal — always.

  • Engineering controls (first choice)

    Air conditioning sized to CIBSE TM52 adaptive comfort criteria, mechanical ventilation, external solar shading, reflective window film, ceiling fans. These reduce the hazard at source — the HSE 'hierarchy of controls' preferred route.

  • Administrative controls

    Flexible start times to avoid the 11am–3pm peak, extra rest breaks in cool areas, rotating outdoor tasks, relaxing dress code, providing chilled drinking water. Sensible for short-term heatwaves; not a substitute for engineering fixes long-term.

  • Personal measures

    Encouraging staff to drink regularly, wear breathable clothing, avoid heavy meals, and report symptoms early. The bottom of the control hierarchy — least effective on its own.

Employer heat FAQs

The questions HR, facilities and safety reps ask every summer.

Is there a legal maximum workplace temperature in the UK?
No. The Workplace (Health, Safety and Welfare) Regulations 1992 require a 'reasonable' indoor temperature but set no upper legal limit. HSE guidance is that 'reasonable' must be judged against activity, clothing, humidity and airflow, and that employers must carry out a thermal comfort risk assessment when conditions become uncomfortable.
What is the minimum workplace temperature in the UK?
The HSE Approved Code of Practice suggests a minimum of 16 °C in indoor workplaces, or 13 °C where work involves severe physical effort. These are guidance figures, not absolute legal limits, but any lower and the employer must justify why the temperature is still 'reasonable' under Regulation 7.
What temperature should an office be in the UK summer?
CIBSE Guide A recommends 21–23 °C for sedentary office work, with an operative temperature not exceeding 25 °C for extended periods (CIBSE TM52 non-domestic overheating criterion). During UK heatwaves, holding an occupied office below 26 °C keeps productivity and comfort within acceptable limits; above 28 °C, the risk of complaints and heat-related illness climbs quickly.
Can employees refuse to work if it's too hot?
There is no automatic right to stop work at a specific temperature. Employees may raise a formal concern under the Employment Rights Act 1996 if they reasonably believe there is serious and imminent danger to health — in extreme heat with vulnerable workers, that argument can succeed, which is why HSE strongly advises employers to act early, document a risk assessment, and consult staff.
Does an employer have to provide air conditioning?
No — the regulation is outcome-based, not input-based. Employers must provide a 'reasonable' temperature by whatever combination of engineering, administrative and personal controls achieves that outcome. But when opening windows, blinds and fans no longer keep temperatures reasonable during heatwaves — increasingly common in the UK — mechanical cooling is often the only practical control that satisfies the regulation.
References

Sources for every claim on this page.

Related reading: cool an office without AC, office AC installation, TM44 statutory inspections, keep cool in a heatwave.

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