In Brief

The absence of a statutory maximum temperature does not remove an employer’s duty to protect workers from foreseeable heat risk.
Indoor workplaces must have a reasonable temperature and sufficient thermometers; high-risk hot processes require a specific heat-stress assessment.
Employers should consider air temperature, radiant heat, humidity, air movement, workload, clothing and individual factors together.
Guidance is not identical to legislation, but it shows practical ways to meet broad legal duties.
Action should begin before illness occurs and should prioritise elimination, engineering and work design over personal cooling products.

The Maximum-Temperature Myth

Questions about workplace heat often begin with a search for one legal cut-off. HSE states clearly that there is no law setting a maximum working temperature because workplaces differ too greatly. A warm office and a foundry cannot be judged by the same air-temperature number, and physical work or protective clothing can create heat strain in conditions that appear moderate.

Some employers misread the absence of a maximum as permission to continue until a worker becomes ill. Others adopt an unofficial temperature as if it were a statutory stop-work threshold. Both approaches are weak. British health and safety law requires a risk-based decision using the actual environment, task, people and controls.

This article explains the framework in Great Britain. Northern Ireland has parallel but separately administered legislation and guidance through the Health and Safety Executive for Northern Ireland, which should be checked for work there.

The Main Duties in Great Britain

The Health and Safety at Work etc. Act 1974 requires employers, so far as is reasonably practicable, to ensure employees’ health, safety and welfare. It also protects others who may be affected. Workplace heat can fall within this general duty where it presents foreseeable risk.

The Management of Health and Safety at Work Regulations 1999 require a suitable and sufficient risk assessment and effective planning, organisation, control, monitoring and review of preventive measures. Employers must consider groups of workers at particular risk and provide comprehensible information and training.

The Workplace (Health, Safety and Welfare) Regulations 1992 require a reasonable temperature in indoor workrooms during working hours. HSE’s Approved Code of Practice gives minimum-temperature guidance, normally at least 16 °C or 13 °C where work involves severe physical effort, but does not prescribe a maximum. Sufficient thermometers must be available so workers can determine the temperature in indoor workplaces.

Those provisions are concerned partly with a reasonable working environment. Where a process or work pattern creates genuine heat stress, broader risk duties and specific HSE guidance become central. The employer cannot show adequate control merely by displaying an air thermometer.

Other legislation may apply. The Personal Protective Equipment at Work Regulations govern required protective clothing, which can increase thermal burden. The Construction (Design and Management) Regulations shape construction planning and welfare. Employers must conduct an individual risk assessment when notified in writing that a worker is pregnant, and consider necessary adjustments.

Law, Approved Codes and Guidance

Legislation states duties. An Approved Code of Practice has a special legal status: following it is not compulsory, but if prosecuted for a relevant breach, a dutyholder who did not follow it may need to show compliance by another equally effective means. HSE guidance generally describes practical ways to comply but is not itself law unless a specific legal provision gives it that effect.

This distinction matters in writing a heat policy. Saying “HSE recommends more frequent breaks” is different from inventing a legal requirement for a fixed break every hour. The employer’s legal duty is to control risk; the appropriate break pattern depends on heat load, workload, clothing and recovery conditions.

Internal action levels are valuable but should be labelled as company controls, not UK legal limits. Explain their evidence base, how they apply and who has authority to act.

Thermal Comfort and Heat Stress Are Different

Thermal comfort describes how satisfied people are with the thermal environment. Discomfort can affect concentration, behaviour and wellbeing. Heat stress is the more serious condition in which the body gains or produces more heat than it can dissipate without excessive strain.

HSE identifies six fundamental factors: air temperature, radiant temperature, air movement, humidity, clothing or PPE insulation, and work rate. Duration and access to recovery also influence accumulated exposure. Individual factors can change susceptibility, but they should not be used to blame workers for a poorly controlled environment.

Employers should respond to comfort complaints because they may reveal failing ventilation or unsafe adaptation, such as removing PPE. Where foundries, bakeries, laundries, compressed-air work, roof spaces or outdoor labour create heat-stress potential, a more specific assessment is necessary.

What a Suitable Assessment Should Cover

Identify heat sources, affected locations and tasks. Observe representative work, including start-up, cleaning, maintenance, breakdowns and peak production. Record sunlight, hot surfaces, steam, airflow, humidity and enclosure. Assess physical effort from lifting, climbing, tool use and movement.

Document the complete clothing ensemble and time needed to leave the hazardous area or decontaminate. Consider shift duration, overtime, recovery areas and whether workers can drink without compromising hygiene or process controls. Include contractors, lone workers and mobile staff.

Use HSE's heat-stress checklist as a structured screen. Complex or high-risk conditions may require competent occupational-hygiene assessment and measurements such as Wet Bulb Globe Temperature. WBGT can support decisions, but it is not a British statutory limit and requires adjustment for work rate and clothing.

Weather forecasts help anticipate outdoor and seasonal conditions, but local microclimates may differ. A roof, excavation, temporary enclosure or process area should be assessed where the work occurs. Worker symptoms and observations remain important even where instruments are used.

Consider workers requiring additional protection through confidential occupational-health processes. New starters and people returning after absence may lack acclimatisation. Pregnancy, some health conditions and medicines may alter tolerance. Make reasonable adjustments and avoid unnecessary collection or disclosure of medical information.

Follow the Hierarchy of Control

First remove the exposure. Can work be automated, completed remotely, moved away from the heat source or scheduled outside the hot period? Can a lower-temperature process or material be used? Design and procurement decisions often provide the greatest opportunity.

Engineering controls include insulation, radiant barriers, process enclosure, extraction of hot air, ventilation, local cooling, cooled cabins and mechanical handling. Verify that cooling does not interfere with contaminant control. Maintain systems and provide indicators that reveal failure.

Administrative measures include reduced work rate, shorter exposure blocks, planned recovery, cooler start times and adequate staffing. Rotation works only when the alternative task has lower thermal demand. Recovery should occur in a genuinely cooler area and include travel and PPE-removal time.

Provide free, accessible drinking water and reasonable opportunities to drink. Hydration is necessary but does not neutralise excessive exposure. Avoid universal drinking quantities and consult occupational health where medical fluid restrictions apply.

PPE remains necessary for residual primary hazards, but it may restrict sweat evaporation and add workload. Select the least thermally burdensome equipment that still protects properly. Personal cooling products may supplement controls after their duration, compatibility, hygiene and weight are assessed.

Acclimatisation and Safe Work Arrangements

Acclimatisation develops through gradual, repeated heat exposure and can decline after time away. Establish progressive exposure for new and returning workers. The timetable should reflect the task, conditions, clothing and individual response rather than copying a foreign prescriptive percentage.

A written plan should define responsibility for forecasts, workplace checks, action triggers, briefings, work modification and emergency response. It should give supervisors and workers authority to pause work when controls fail or symptoms occur. Production targets must not silently override the plan.

Consult workers and safety representatives. They can identify hot spots, inaccessible water, missed recovery and PPE problems. Provide information in a form and language the workforce understands, including agency and contractor staff.

Symptoms and Emergency Action

Early heat illness may involve headache, dizziness, nausea, weakness, cramps, heavy sweating, poor concentration or loss of coordination. Stop exposure, move the person to a safe cooler place, remove unnecessary outer clothing when other hazards permit, begin cooling and follow first-aid arrangements.

Confusion, collapse, seizure, altered consciousness or severe coordination loss may indicate a life-threatening emergency. Call 999 and begin rapid cooling without delaying for a perfect measurement. Do not leave the person alone. Plan how emergency services will access remote, elevated, enclosed or contaminated locations.

Investigate every suspected case. Review environment, workload, PPE, acclimatisation, breaks, staffing and supervision rather than assigning the event to personal fitness alone.

Demonstrating Effective Management

Keep the risk assessment, monitoring records, trigger decisions, control checks, training and incident reviews. Record why internal thresholds were selected and what happens at each level. Review after process, building, shift or PPE changes and after unusual weather or symptoms.

Useful evidence shows that controls reduce heat load in practice. Compare conditions before and after ventilation or shielding, inspect recovery areas and consult workers. A written policy without operational evidence is insufficient.

Sysco Environmental can support employers with workplace heat-stress assessment, monitoring and control advice. Our role is to help define the question, obtain representative evidence and turn it into a proportionate plan.

UK law does not need one maximum temperature to require action. General and workplace duties, applied through a suitable assessment, already require employers to identify foreseeable heat risk and control it before workers become ill.

No Maximum Temperature? Your Legal Heat Duties Still Apply