Keep it cool: dealing with heat stress

For construction workers working in Faversham on 1 July last year, shade, water and plenty of breaks were essential as the Kent town recorded the UK’s hottest temperature, nudging the mercury to a sweltering 35.8°C.

Last year would go on to become the country’s warmest recorded summer, according to the UK Met office, with a mean temperature of 16.1°C logged from 1 June to 31 August, beating the previous record of 15.76°C set in 2018.

As extreme heat becomes a more regular occurrence, health and safety managers in construction are having to build heat stress awareness into their strategies. The shade, water and rest approach may sound simple, but at its core is robust communication, forward planning and a knowledge of the legislation underpinning working in heat.

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 says employers need to assess risks, including heat stress, and implement appropriate control measures. 

The Health and Safety Executive, in its guidance on temperature in the workplace, suggests a “thermal comfort” range between 13°C and 30°C, dependent on the type of work undertaken. 

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

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 assesses how a worker’s body will respond to heat stress over time.  

EU Directives, including the Framework Directive 89/391/EEC, requires employers to ensure worker safety under all foreseeable risks, including thermal risks. This is interpreted and enforced by each member state. For example, while Spain has no fixed temperature limit in place, 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”.

Regulation 13 (4) (c) of the Construction (Design and Management) Regulations 2015 states that the principal contractor must ensure that facilities complying with the requirements of Schedule 2 are provided throughout the construction phase. 

Schedule 2 outlines the minimum welfare facilities required on a construction site, which includes “an adequate supply of wholesome drinking water” and “a supply of clean, hot and cold, or warm, water”, the latter as part of the site’s washing facilities.

In April this year, the HSE fined a West Midlands construction firm for failing to offer such welfare provisions to workers across four of its sites. The HSE inspector who carried out the investigation, Natalie Spurrier, said: “The provision of suitable welfare facilities such as hot running water and basic rest facilities are the minimum all workers should expect – they aren’t a luxury.”

Heat stress takes place when the body’s way of controlling its internal temperature starts to fail. The process is affected by factors including temperature, work rate and humidity and work clothing including PPE.

It can affect people in different ways, and some are more likely to suffer than others. Symptoms include heat exhaustion ie fatigue, dizziness, nausea, headache and heat stroke ie hot dry skin, confusion convulsions and eventual loss of consciousness. It can result in death if not detected at an early stage. More tangible warning signs include muscle cramps, heat rash and severe thirst.

Doha Mater is EHS director at PepsiCo and oversees workforces in Africa, South Asia and the Middle East where temperatures regularly hit above 40°C in the summer months. As such, outdoor work is prohibited between the hours of 12pm and 4pm, when the sun is at its most intense. 

Speaking on a NEBOSH webinar on heat stress, she shared insight into how, alongside legislative alignment, the nature of the risk means administrative controls (the way people work) should be applied as opposed to an engineering control strategy (removing the hazard). “One of the admin controls would be making sure that our employees are properly hydrated and, part of making them properly hydrated, is encouraging them to do so or providing the right facilities for them,” she said.

Offering a shaded area and a supply of water is, at its simplest, 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 may be ideal for large outdoor worksites, such as oilfields or solar farms. They can include a range of water dispensers, and ice chests as well as cooling fans, misting systems and shade awnings.

Signage around hot work areas is particularly useful and the asset may be located near restrooms or break areas. Ideally, it should be configured to the workforce it serves considering the number of employers, the types of tasks being undertaken and the environment, which in construction, could potentially be a dusty one. 

Ideally, the hydration station or water point acts as a reminder that workers should build hydration breaks into their schedules rather than ignoring it, which helps to implement good hydration practice into a workforce.

Visuals, automated reminders and announcements are an important part of an overall management strategy, but having a human touchpoint enables supervisors to carry out important physical checks.  

As well as physical symptoms, heat stress can also affect cognitive behaviours, a key issue for those operating in high-risk environments such as construction sites. Mater cited awareness of early warning signs such as dizziness, sweating and confusion, which can be 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 voluntarily go and look for those early signs,” she said.

This awareness comes from a healthy safety culture, implemented from the top down and actioned robustly throughout management lines, including supervisors. Reminding workers to bring water on board may be a basic administrative measure, but it can help strengthen the relationship between workforce and management by demonstrating genuine care for employees’ wellbeing.

One of the factors that can accelerate heat stress among workers is PPE. It’s a conundrum suppliers face when designing workwear that must conform to standards while providing a level of comfort. Some PPE include moisture-wicking fabrics, but it often comes down to working closely with suppliers to source clothing that provides the necessary protection while also offering cooling properties. However, most materials found in PPE can contribute to heat stress if worn in extreme conditions. 

It’s a dichotomy meaning mitigation takes on more of a challenge. 

An increased awareness of workers’ schedules, length of shifts and hydration becomes paramount, but it comes down to good habits and a culture that empowers and encourages while ultimately emphasising the importance of taking breaks and staying hydrated. The knock-on effect can be extremely positive for a workforce, creating better morale, better health and perhaps productivity on site.

Already this year, the 26.5°C recorded on 7 April was the second warmest in the first half of April in 80 years, and few would be surprised if this summer continued the trend of record-breaking temperatures.