Playing it cool

Tuesday, 26 August 2025

NEBOSH

With longer, frequent and more intense heat waves, workforces are becoming more exposed to heat stress, but how does the profession manage one of the emerging occupational health risks?

This summer has already seen several heatwaves in the UK and Europe.

In Portugal, the town of Mora averages 32°C during the summer months. In June, the mercury notched 46.6°C. Meanwhile, in the UK, the highest temperature of the year so far was recorded on 1 July, when 35.8 °C was measured in Faversham, Kent.

The Met Office's State of the UK Climate 2024 report, published just as the country and Europe experienced its third heatwave of the summer, concluded that "extreme weather is now the new normal."

It says that extreme heat days are becoming more common, while days exceeding 8°C and 10°C above average have tripled and quadrupled, respectively.
It means workplaces are also getting warmer, and health and safety professionals are having to acknowledge and implement more stringent mitigations against heat stress. The sectors and areas of work most vulnerable include agriculture, lone working, mining, and construction. In the US, heat-related illness among construction workers is one of the leading causes of death.

On a global scale, the International Labour Organisation says that 2.4 billion workers are being exposed to excessive heat, resulting in more than 22 million non-fatal injuries annually.

Under stress

Heat stress takes place when the body is unable to control its internal core temperature, leading to a spectrum of symptoms that range from fatigue, headaches and vomiting to potential seizures and a loss of consciousness. The process is affected by factors including temperature, hydration, work rate & intensity, and work clothing, including PPE.

From a global compliance perspective, and in the absence of strict legal limits, ISO Standards aligned with global heat analytical systems are useful markers. ISO 7243 assesses risk using the Wet Bulb Globe Temperature (an index that measures heat stress through air temperature, humidity, radiant heat and wind speed) while ISO 7933 interprets heat stress through a Predicted Heat Strain (PHS) model, which works out how a worker's body will respond to heat stress over time.

EU Directives, including the Framework Directive 89/391/EEC, require employers to ensure worker safety under all foreseeable risks, including thermal risks. Each member state interprets and enforces this. In Spain, for example, while no fixed temperature limit applies, a Royal Decree ratified in May 2023 means work must be adapted or suspended if an official orange or red alert is announced or "if preventative measures do not sufficiently reduce risk."

In the UK, while there is no legal maximum working temperature, employers have duties under the Health and Safety at Work etc. Act 1974, to ensure risks around high temperatures are managed. The Management of Health and Safety at Work Regulations 1999 say employers need to assess risks (which includes heat stress) and implement appropriate control measures. In its guidance on temperature in the workplace, the Health and Safety Executive suggests a "thermal comfort" range between 13°C and 30°C, dependent on the type of work undertaken.

Doha Mattar is EHS Director at PepsiCo and oversees workforces in Africa, the Middle East & South Asia, where temperatures regularly hit above 40°C in the summer months. As such, in some countries, outdoor work is prohibited between the hours of 12 and 4 pm, when the sun is at its most intense. Speaking on a recent NEBOSH webinar, she said adhering to any regulation around heat "is essential and a basic fundamental … ensuring that if we have any legal or compliance obligations that we actually follow them".

She shared insights into how, alongside legislative alignment, the nature of the risk significantly relies on administrative controls (minimising risks through procedures, training, monitoring), which should be applied as opposed to an engineering control strategy (reducing or eliminating exposure to the hazard).
"One of the admin controls would be making sure that our employees are properly hydrated, and part of making them properly hydrated or encouraging them to do so is essentially providing the right facilities for them," she said.

Hydration and the correct delivery facilities are the cornerstone of heat stress management. Still, Doha also cited awareness of the risks as key and a proactive approach to spotting early warning signs such as dizziness, sweating, and confusion, which can be quite subtle.

"We do have sight of what could be going wrong and it actually looks very natural. People start getting lightheaded, they might feel nauseous, have a headache … in the workplace we need to make sure that we intentionally go and look for those early signs."

Data analysis

Technology and data analysis is also enabling employers to get visibility of extreme conditions that can form a predictive approach to heat stress management.
Data can be collected through wearable sensors, including arm bands, chest straps, and even stick-on patches. Software on a worker's smartphone can also provide input.

The goal is to record real-time core body temperature (the significant marker of heat stress) and combine this data with external environmental analytics such as the Web Bulb Globe Temperature index or a PHS model. It enables establishing a safety point or cut-off so that measures can be applied accordingly.

To create that visibility, users can monitor data on a software platform or dashboard fed by input from the wearable monitors and global index readings. Predictability comes when risk assessments are configured into the programme. For example, a forecast of a high humidity figure can ensure a risk assessment is actioned before workers set out on that day. The system can also be supplemented further with data from permits and training documents. However, the technology can only thrive with management & workforce buy-in.

"Nothing happens without people," says David Picton at EcoOnline, "It's about the way you engage people and for them to see what's in it for them and what they can get out of the tech."

Having previously held Senior positions at Carillion, Sky, Lenova and National Highways (where he was Interim Executive Director in 2018), he says technology can only operate in a strong safety culture; it is, he explains, the only way to overcome a workforce's resistance to change.

"Of course, people have concerns over data, over biometric data. If you're starting to ask them to wear a device, there are privacy concerns or perhaps a perspective that they're being monitored or checked in on. So, before you even consider rolling out this kind of technology, you need to work with the workforce to explain your goal. But as you go through the process, you can show people the benefits, such as seeing the early warning signs."

He suggests that successful insight from a trial group can change attitudes once shared with the wider workforce. For example, before the technology, a worker may have continued working when the now-established safety cut-off point was indicated. "You can get that kind of an early win that helps the rest of the workforce to see it in the context of what it can do for them."

Taking regular breaks

At its simplest, offering a shaded area and a supply of water is a hydration station. However, these facilities can vary in design based on the work environment. A basic asset could be a series of three or four large igloo-style water coolers with reusable cups, located near break areas and awareness posters around hydration habits.

Mobile hydration carts or trailers for large outdoor worksites such as oilfields or solar farms are common internationally. They can include a range of water dispensers and ice chests, as well as cooling fans, misting systems and shade awnings. Some large factories or warehouses maintain year-round water stations with bottle-filling facilities. Signage, particularly around hot work areas, is useful, and the asset may be located near restrooms or break areas.

Doha says the location of these facilities is essential. "Providing easy access to fluids seems like it's very basic, but we sometimes actually overlook its importance; we overlook the step of giving it a close eye to make sure that water is easily accessible to everyone."

These stations also encourage workers to take a break from their duties. However, there remains a culture of bravado with many opting to continue working in extreme heat to get a job done or meet a deadline, yet are unaware their core body temperature could be creeping up to dangerous levels.

Picton cites the importance of accountability channelled through this central water point, stating that the goal is to get workers building hydration into their work schedule rather than ignoring it. "It's about trying to get people to understand that they've got personal responsibility, which a hydration station can give a bit of a psychological focus to."

Simon Toseland is Risk Assurance Director at Veolia, having previously been Head of Health, Safety and Fire at Birmingham Airport. He suggests a hydration station should be configured to the workforce it serves with employers considering "the numbers of employees, the types of tasks they're undertaking as well as the environment, which could be a dusty one.

"I think it needs a lot of thought and, obviously, just keep making sure that it's well supplied. So ideally you would want from a plumbed-in system, but that's not always viable, so it's just making sure then that you're managing the water accordingly - that there's good supplies and stocks".

Toseland observes that workers' attitudes to taking breaks and staying hydrated have changed over the last ten years. This has been forced in part by consistently higher temperatures and an awareness of heat stress's correlation with safety incidents. He explains: "We're a lot more informed now about the links between those human factors, tiredness and fatigue, which can be caused by dehydration and how that is linked to people's performance and accidents."

Doha agrees. She says one of the symptoms of heat stress is the detrimental effect on perception and focus, which can lead to dangerous workarounds. "They [the workers] start taking shortcuts. And the problem with shortcuts is they usually lead into incidents. If we go back and investigate, there will be a correlation between their work outdoors and how this stress caused them to sometimes take those shortcuts."

But how can you negate this? Is it even possible? "It's really about the specific plan for your site and your activities that makes all the difference," she counsels. "It's about the nature of work, the nature of employees, and the nature of shifts.”

Dynamic workforce

It's a challenge faced by Louise Sampson, Safety, Health and Wellbeing Business Partner at Affinity Water, who oversees a transient workforce that rarely stays in one place, and if they do, it's not for long.

The utility firm provides water to 3.9 million people across the south east of England, which involves maintaining and repairing a vast underground infrastructure, with a large part of the network only accessible by road excavation.

Communication, including webinars, briefings, and other information, is key to Sampson's strategy. As we're talking, she brings up a recent memo: "It was a general one to the whole business which said to remember to take enough breaks and stay out of the sun if feasible, review work times and then we push out links to NHS guides on the topic."

Sampson explains that job site locations can be challenging in extreme heat. "Workers are often on a busy highway with traffic that generates more heat. There is probably little shade as the work site is often in the middle of the road. "Ordinarily, in such conditions you would work in the early part of the day or later on, but if there's a burst water main that's flooding a customer's house, or if people are unable to access drinking water, then you have to just go out and do it."

As well as attending emergency callouts, teams are deployed to planned maintenance jobs, classified as non-essential works. These projects can be delayed if temperatures are deemed too high. "When we get extremely hot weather and if there are planned works that are not urgent, we might postpone them and deliver the essential projects," Sampson says. "It means that we are in this instance not sending out workers unnecessarily."

When workers begin a shift, they select the required materials, fittings and other equipment from a central stock yard. Here, Affinity Water has a large supply of bottled water; large multi-packs that are loaded alongside pipes and PPE. However, once dispersed, it can be difficult to monitor hydration habits. Jobs are often carried out by teams of two who might complete three to four projects in one day. They are rarely in one place for a long period of time, so a central hydration zone just doesn't exist.

Here, Sampson's strategy of pre-shift briefings, general communication and the role of supervisors come into play. "They're [the supervisors) are in regular contact and will go around and audit the teams' equipment, checking their vans and if they've got a good supply of water," Sampson explains. "A support driver can also give out more refreshment, too, when they bring barriers or other equipment."

In the workplace, Doha says the role of supervisors in reminding workers to hydrate is another simple admin control that can also strengthen the bond between the workforce and management. "The interaction itself really demonstrates the care we have for our employees and that we take heat stress very seriously."

She says visuals, automated reminders and announcements are an important part of the overall strategy but having a human touchpoint enables the supervisor to carry out an important physical check. "They should be going around during their walks, looking out for any warning signs that we discussed before."

PPE

One factor that can accelerate heat stress among workers is PPE. Suppliers face a conundrum when designing workwear that must conform to standards while providing a level of comfort, although arc flash PPE has very little leeway around compliance. Those in the utility sector are vulnerable to arc flash during excavation work. A damaged water pipe can be buried deep in a complicated crisscross of other infrastructure, including electrical cables, which can trigger a potentially fatal electrical explosion if struck. It means the protective clothing's layered make-up (an outer flame-resistant shell and an inner thermal liner to trap heat and slow the transfer of radiant and connective energy) is mandatory, however in hot weather and with little ventilation, donning this head-to-toe PPE can be extremely uncomfortable.

"Obviously this isn't conducive to working in hot conditions," Sampson admits, "but if you don't wear it and you do get an arc flash, you're going to be exposed to life-threatening burns. At its source, the temperature of arc flash can reach 19,000°C."

Some PPE has moisture-wicking material as an extra layer, but for Sampson, it's a case of working closely with suppliers to find clothing that protects while offering some cooling properties. Another option on the market is a cooling vest to fit underneath the garment - but while the PPE undeniably protects workers from an extremely dangerous hazard, it does so with materials that can contribute to heat stress. For Sampson and those who work in the utility sector, the dichotomy means mitigation takes on more of a challenge.

Again, this comes back to good habits and a healthy culture, one that empowers, encourages, and emphasises the importance of taking breaks and staying hydrated. "It's doable," Doha concluded in the webinar, highlighting the positive impact it can have on employers. "If I'm properly hydrated, I will definitely have much better morale and much better health, and I will definitely perform a lot better in my life in general, but also at work."

Understanding the future

Climate change is reshaping the landscape of workplace health and safety, and NEBOSH's Dee Arp is urging the sector to face the challenge head-on. "OSH professionals need to understand the impact of extreme weather and rising temperatures; in doing so, they can protect vulnerable workers and design safer, more resilient workplaces."

NEBOSH incorporates a unit on heat stress, covering risk assessment techniques and effective control strategies. With heat waves becoming longer, frequent, and more intense, it's no wonder heat stress is becoming one of the emerging risks of occupational health.

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