It’s getting hot in here: why employers need to act on heat risks

The UK was not built for the climate it is now beginning to experience. That was the stark warning from the Climate Change Committee (CCC) in May, as it urged the government to consider maximum workplace temperature rules to protect people from intensifying heatwaves.

The CCC has said extreme heat is now the greatest health risk from climate change facing the UK, warning that more than 90% of existing homes could overheat during more extreme heatwaves by the middle of the century. The Committee also argued that cooling technologies, including air conditioning, heat pumps and green shading, will need to become a higher priority in schools, hospitals and workplaces.

For employers, this is no longer a distant climate scenario. The record-breaking May heatwave has already brought the issue sharply into focus, with parts of the UK exceeding 30°C and Kew Gardens provisionally reaching 34.8°C, according to ITV News.

Heat stress occurs when the body’s ability to regulate its internal temperature begins to fail. Photograph: iStock

Public behaviour suggests consumer behaviour is shifting too: Google searches for air conditioning units in the UK have risen by 40% over the past five years. The question is no longer whether heat stress should be taken seriously, but how quickly organisations can build it into everyday risk management.

What is heat stress? 

Heat stress occurs when the body’s ability to regulate its internal temperature begins to fail. It can result from a combination of environmental conditions, physical effort, clothing, acclimatisation level, personal protective equipment (PPE) and individual health factors. Early symptoms can include fatigue, thirst, headache, dizziness, heat rash, muscle cramps and poor concentration.

If exposure continues, workers may develop heat exhaustion, with nausea, weakness and fainting. In severe cases, heat stroke can occur, which is a medical emergency, and can result in death if not treated quickly and correctly.

The safety implications extend beyond health symptoms alone. Heat can impair judgement, slow reaction times and reduce concentration. 

In offices, this may affect wellbeing and productivity. In safety-critical environments, such as construction, manufacturing, logistics, utilities, transport, warehousing and food production, the consequences can be much more serious.

A fatigued worker operating machinery, working at height or handling heavy loads may be at greater risk of error or injury long before they show severe signs of illness.

Do we need a maximum workplace temperature? 

The debate around maximum workplace temperatures has gained traction. Although the Health and Safety Executive’s (HSE’s) Approved Code of Practice on the Workplace (Health, Safety and Welfare) Regulations suggests a minimum temperature for working indoors (depending on the nature of the work), with the aim of providing “reasonable comfort”, the UK has no fixed legal maximum temperature at which work must stop.

HSE expects employers to protect the welfare of staff, so far as is reasonably practicable, in accordance with the Health and Safety at Work Act 1974.

This allows for a degree of variability that may leave some employees more vulnerable than others, as heat stress is an individualistic hazard, further confounding the argument for a single upper threshold. During heatwaves, this can create uncertainty for employers and workers alike, posing the question ‘when is it simply uncomfortable, and when is it unsafe?’

The CCC has not proposed a specific UK limit, but BBC News noted that it pointed to Spain, where indoor maximum legal working temperatures are 27°C for sedentary work and 25°C for light physical work.

Trade unions have also repeatedly called for a legal maximum working temperature in the UK. However, British Safety Council has warned against relying solely on a rigid, one-size-fits-all threshold. As it noted in its official position on the issue, heat risk depends on more than air temperature alone.

Parts of the UK this May exceeded 30°C including in London. Photograph: iStock

Humidity, airflow, workload, PPE and individual vulnerability all affect how heat is experienced and the level of risk it creates. 

It is important to note that the short and extreme nature of heatwaves, especially in the UK, means workers can lack acclimatisation to working in this extreme heat, and are therefore more vulnerable to the associated adverse health impacts, like dehydration, increased tiredness and dizziness.

A temperature that is manageable for a lightly dressed office worker sitting near ventilation may be dangerous for someone carrying out strenuous manual work in direct sun, wearing protective clothing, or operating in a poorly ventilated warehouse.

Similarly, indoor process environments that involve working in high temperatures – such as bakeries, foundries, commercial kitchens, laundries, boiler rooms and manufacturing plants – may present heat stress risks throughout the year, not just during summer.

Employers therefore need to ensure they do not treat heat health risks as a hot weather issue only. In many sectors, it is a foreseeable operational hazard, all year-round.

How can workplaces manage the health risks from high workplace temperatures and working outdoors in heatwaves? 

As with all occupational hazards, the starting point should be a suitable and sufficient risk assessment. Employers should identify where heat exposure occurs, who may be affected and what factors could increase vulnerability.

This includes considering workers who are older, pregnant, new to the job, returning after absence, taking certain medications, managing health conditions or staff who are not acclimatised to hot conditions. 

Employers should also consider the risks high temperatures pose to agency workers, contractors and lone workers, all of whom may be less familiar with site procedures or less likely to raise concerns.

Control measures do not always need to be complex, but they should be planned and set in place, ready to be activated, before temperatures peak. In workplace buildings, employers can improve ventilation, use blinds or reflective film to reduce solar gain, move workstations away from heat sources, provide fans or air conditioning where appropriate, and create cooler rest areas. 

Outdoor work can be rescheduled to cooler parts of the day, and arrangements made to ensure workers have access to shaded rest facilities and can take more frequent breaks.

Physically demanding tasks can be rotated among team members, or the expected pace of work can be reduced, and non-essential strenuous work postponed during heat alerts. Free, cool drinking water should be readily available, and workers should be encouraged to drink regularly rather than waiting until they feel thirsty. 

Also, workers who aren’t used to working in hot environments are particularly vulnerable to heat stress and are likely to require additional rest time until they build a level of acclimatisation to the heat and humidity.

Communication, instruction and training

Communication is equally important. Workers and supervisors should understand the symptoms of heat stress, know how to report concerns and feel confident that action will be taken by managers to reduce the risks to their health.

Toolbox talks, briefings and signage can help, particularly for workforces with a high turnover, such as the construction industry or when temporary staff are employed, for example on a seasonal basis. 

Supervisors should also be trained to spot early warning signs of workers struggling to cope with high temperatures, because affected individuals may not always recognise the risky symptoms themselves.

There should be a clear escalation process defining when work will be modified, paused or stopped if high temperatures and humidity are negatively affecting the health and wellbeing of individuals or teams, and all managers and staff should understand (and be regularly reminded of) the process for accessing and receiving first aid or medical assistance if anyone becomes unwell due to the heat.

The rise of hybrid and home working adds another dimension that employers need to consider when seeking to protect worker health from high temperatures.

Many UK homes are not designed with structural and other features to reduce the effects of prolonged heat, and some workers may be based in loft rooms, small flats or poorly ventilated spaces without access to mechanical cooling, such as fixed or portable air conditioning units. 

The rise in searches for air conditioning suggests households are increasingly looking for ways to adapt, but employers’ duties do not disappear when work is carried out remotely. During heatwaves, they should consider ways of supporting workers to cope with high temperatures.

This might involve approaches such as granting flexible working hours (such as early morning starts before temperatures reach their peak), conducting regular welfare checks, providing advice on ways of keeping workspaces cool and allowing workers to move to an alternative cooler workplace where possible, such as an air-conditioned local co-working space.

Heat stress and PPE

PPE presents a particular challenge. Although PPE may be essential for protecting the wearer against other hazards, it can also trap heat and restrict evaporation of sweat. Employers should therefore consider whether lighter, breathable or task-specific alternative types of PPE are available that will reduce the worker’s body temperature without compromising protection. 

As well as considering alternative types of PPE that both reduce body temperature and improve the rate of sweat evaporation from the skin, employers should consider if the amount of PPE worn can be reduced while still ensuring adequate protection, or if other risk controls will reduce or eliminate the need for PPE.

However, if workers cannot wear less PPE, or more comfortable and lighter PPE cannot be provided – such as breathable fabrics that increase sweat evaporation or clothing that incorporates personal cooling systems – it becomes even more important to consider changes to work-rest schedules, better hydration, general workplace cooling measures and effective supervision to ensure workers do not become dangerously hot while wearing PPE.

How do you monitor heat stress? 

A mature strategy for managing the health risks from high temperatures and heat stress also depends on having good information of the level and nature of the risk that high temperatures and humidity pose to worker health. 

Air temperature alone is a limited guide to whether a workplace temperature is comfortable or whether there is a risk of workers suffering heat stress because it does not account for other environmental and personal factors, like humidity, radiant heat, airflow or workload. 

In higher-risk environments, Wet Bulb Globe Temperature (WBGT) monitoring can provide a more rounded measure of heat stress conditions and help inform decisions about how best to amend work-rest regimes to better protect workers from the impacts of heat and humidity. This is where appropriate instrumentation can support professional judgement. 

Modern heat stress monitors use WBGT index values to help safety teams evaluate thermal risks in working environments, decide how and when to ensure people stop working and take other measures like removing PPE to protect themselves from high temperatures and the risk of heat stress, and support reporting and analysis on how well thermal comfort at work is being managed.

WBGT measurements use multiple temperature sensors to consider radiant heat, relative humidity and potential air movement in the WBGT index calculation. Used properly, these instruments can help ensure that heat stress management is not based on possibly inaccurate guesswork but instead on data that informs more effective, evidence-based controls.

Conclusion

The public debate about the merits or otherwise of a legal maximum working temperature will no doubt continue, and we may see further regulation in this space, but employers should not wait for the introduction of any new, specific legal duties before acting to protect workers from health risks arising from high temperatures.

Existing legal duties under UK health and safety law already require employers to manage foreseeable workplace health and safety risks, and extreme heat is now plainly foreseeable.

Heat stress management is not about stopping work every time the sun shines. It is about recognising when conditions, tasks and people combine to create risk, and then applying proportionate controls. As the UK climate changes, protecting workers from heat will become a routine measure of good health and safety leadership.

For more information and advice, see:
casellasolutions.com

Stephen Sandford is technical product manager at Casella