Author Bio ▼

Dr Karen McDonnell is Head of Global Relations at the Royal Society for the Prevention of Accidents (RoSPA). She is also the immediate past president of IOSH.
June 25, 2024

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Feeling the heat? – Tips on heat stress

With UK temperatures beginning to rise this week in many areas, we revisit this article from Dr Karen McDonnell, Head of Global Relations at the Royal Society for the Prevention of Accidents (RoSPA), who offers some tips for avoiding heat stress at work.

Worker shielding his eyes from the sunlightExposure to excessive heat while working, whether indoors or outdoors, can be hazardous to health.

So, how can employers and employees reduce the risks?

Heat stress happens when the body’s way of controlling its internal temperature starts to fail. Symptoms can include an inability to concentrate, muscle cramps, heat rash and severe thirst. It can lead to heat exhaustion and heat stroke, which is potentially fatal.

In addition, exposure to excessive heat can result in lethargy, poor decision-making, sweaty palms, fogged-up safety glasses and dizziness – all of which can increase the risk of injuries.

According to the International Labour Organization 2019 report Working on a warmer planet: The impact of heat stress on labour productivity and decent work, the rise in global temperatures caused by climate change will make heat stress more common. By 2030, it’s estimated that 2.2 per cent of total working hours worldwide will be lost to high temperatures – a productivity loss equivalent to 80 million full-time jobs and an estimated cost of US $2,400 billion.

Who is affected?

Heat stress can affect those working outdoors in high temperatures, for instance in sectors such as agriculture, construction, refuse collection and tourism, but also employees in indoor environments which are hot because of the processes being carried out, restricted spaces and/or inadequate ventilation.

Some examples of indoor jobs which can involve exposure to heat include foundries, laundries, commercial kitchens and bakeries, boiler rooms, glass and rubber manufacturing plants, compressed-air tunnels and power plants.

The causes contributing to heat stress can be considered in three broad categories when assessing the risks:

Environmental risk factors

  • Ambient temperature – a temperature higher than that of the human body means that a person will gain heat from their surroundings. The ILO says that temperatures above 24–26°C are associated with reduced labour productivity, while at 33–34°C, a worker operating at moderate work intensity loses 50 per cent of his or her work capacity
  • Ambient humidity – high humidity reduces the body’s ability to cool down through sweating
  • Air movement – more ventilation will help cool the body
  • Direct heat source – this could be the sun or hot surfaces, or it could be something like a hot engine or furnace.

Job risk factors

  • Workload – is it high or low?
  • Rate of work – is it fast-paced or slow?
  • Type of work – is it strenuous work or sedentary? The more active the work, the higher the risk
  • What clothing is worn? If a worker must wear personal protective equipment (PPE) such as a hard hat, gloves, a protective suit or a mask, or carry heavy items, this can restrict air flow and prevent heat from escaping, making heat stress more likely.

Personal risk factors

  • Health – workers with health conditions such as diabetes or heart disease, illnesses such as respiratory infections and/or on certain medications may be more susceptible to heat stress
  • Dehydration – this affects a person’s ability to lose heat
  • Physical fitness – the lower this is, the higher the risk of heat stress
  • Obesity – also increases the risk
  • Alcohol/drug consumption – can reduce heat tolerance and increase dehydration
  • Fatigue – this could be sleep deprivation or accumulated fatigue. Both increase the risk of heat stress
  • Level of experience – inexperienced workers may not know how to adapt their pace of work in hotter conditions. In addition, workers who arrive in hotter climates, especially those who have come from a cooler climate, must be acclimatised to the hot weather to allow the body to slowly adapt.

How can the risks be reduced?


Here are some things that employers can do to help reduce the risks:

  • Monitor and share information on local weather conditions
  • Provide conveniently located, accessible cool drinking water and encourage staff to drink water regularly to avoid dehydration
  • Allow workers to acclimatise to their environment and identify which ones are assessed as fit to work in hot conditions
  • Include advice on heat risks in routine health and safety training
  • Enable and encourage staff to take their breaks in the shade/cooler areas if possible
  • Smart planning: scheduling work to minimise exposure to high temperatures
  • Engineering controls can be put into place, for instance increasing air velocity, reducing humidity, using fans or air conditioning, using reflective or heat-absorbing shielding or barriers
  • Use a buddy system where workers observe each other for signs of heat stress
  • Consider specialised personal protective clothing which incorporates personal cooling systems or breathable fabrics.


heatwaveWhile employers are legally responsible for managing health and safety risks in their businesses, workers also have a duty to co-operate with employers and to take care of their own health and safety and that of others who may be affected by their actions. Here are some tips to avoid heat stress:

  • Don’t over-exert yourself when you start a new job in hot conditions, especially if you have just arrived from a cooler country. Acclimatise yourself to hot weather
  • Wear loose-fitting and light-coloured clothes when outdoors
  • Work under the shade where possible
  • Drink lots of water – at least 500ml every hour
  • Take regular breaks in cool shaded areas
  • Sponge yourself with water during breaks
  • Adopt a healthy lifestyle with proper meals and sleep
  • Wear sun cream when outside and remember to reapply regularly to avoid sunburn
  • Avoid extreme changes of temperature
  • Be particularly aware when working in already hazardous environments, such as with machinery, chemicals or when working at height
  • Look out for your colleagues. If you see someone struggling in the heat, take action and let somebody know.

What to do if heat stress strikes

Dr Karen McDonnell

If you notice someone with signs of heat stress:

  • Move the person to a shady or cooler area
  • Give them cool water to drink
  • Loosen or remove the person’s clothing
  • Cool the skin: Apply cool water; fan the person; place ice packs wrapped in cloth under the person’s armpits, on the neck or in the groin area.

If the person is still unwell after 30 minutes of resting in a cool area and drinking fluids, they may have heat stroke. Other symptoms of heat stroke are:

  • A very high temperature
  • Hot skin that’s not sweating and might look red
  • A fast heartbeat
  • Fast breathing or shortness of breath
  • Confusion and lack of coordination
  • A seizure or fit
  • Loss of consciousness.

If you think someone has heat stroke, call an ambulance immediately.

What makes us susceptible to burnout?

In this episode  of the Safety & Health Podcast, ‘Burnout, stress and being human’, Heather Beach is joined by Stacy Thomson to discuss burnout, perfectionism and how to deal with burnout as an individual, as management and as an organisation.

We provide an insight on how to tackle burnout and why mental health is such a taboo subject, particularly in the workplace.


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