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Nobody likes working in the heat. We’d much rather take a break. But sometimes, it is impossible to escape. For instance on hot summer days or warm production environments. In some workplaces, it is always hot, like installations, foundries or enclosed spaces. 

In this article, we focus on ‘heat stress’. For more information about the risk of burns, we refer you to the page ‘Fire, sparks and weld spatter’.

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Heat Stress

Naast dat de huid kan verbranden, is er ook risico voor het gehele fysieke gestel. Mensen hebben een lichaamstemperatuur van gemiddeld 37 graden Celsius. Door zeer hoge omgevingstemperatuur, zware inspanning  en veiligheidskleding raakt je lichaam oververhit. Dit noemen we hittestress (heat stress). Met als ernstigste gevolg het verliezen van je bewustzijn of zelfs overlijden.
Medewerkers raken oververhit door twee belangrijke oorzaken:
1. The environmental conditions in which they work
2. De lichaamstemperatuur gegenereerd door fysieke arbeid.

Hitte gerelateerde problemen ontstaan als de temperatuur van het lichaam stijgt en niet meer wordt beheerst door het lichaam. Hier heeft het dragen van veiligheidskleding en PBM’s ook invloed op. Hittestress komt dus niet alleen voor tijdens de zomer.

Cooling mechanisms
The human body uses its own mechanisms to deal with heat. Your body cools off through radiation and convection, but above all by evaporating sweat and bringing blood to the skin surface. However, the higher the humidity, the harder it is for the sweat to evaporate. When wearing poorly breathing clothing (like safety clothing) that evaporation effect is reduced even more. The clothing acts as a ‘greenhouse’, causing the body’s temperature to keep rising. 

We distinguish three kinds of heat:
  • Conductive heat: High temperature spreads across the entire surface, so it is important to wear clothing with a low thermal conduction.
  • Contact heat: When you touch a hot object, you can get burns. Good PPG, like clothing and gloves, can help protect you.
  • Radiation heat: When an object gets very hot, it will radiate heat, which, at very high temperatures, will cause burns.


Heat stress starts out small, but can escalate quickly unexpectedly. Do you recognize one of the symptoms listen below? Make sure to take measures immediately!
  • Loss of concentration
  • Muscle cramps
  • Heat rash
  • Serious thirst (often a late sigh of heat stress
  • Fainting
  • Overheating: tired, dizzy, nauseous, headaches, moist skin
  • Heat stroke: heat dry skin, confused, absentminded and possible loss of conscience.
  • This face can lead to death when not recognized in time. 
These symptoms will be more serious when people are working in the same circumstances for longer. Risk group: people over 45, overweight, cardiovascular diseases, high blood pressure, on medication. 

There are also other consequences: the wellbeing and safety of your employees is put at risk. Loss of concentration increases the likelihood of mistakes and unsafe working practices. If one of your employees suffers from heat stress, they can also pose a risk for their colleagues!


How can you determine ‘heat stress’? And when can we speak of heat stress?
In the NEN-ISO 7243D, it is explained how you can measure the core temperature: using a WBGT matrix. The humidity and ambient temperature together determine the core temperature. For a precise determination you will, of course, have to perform a WBGT measurement with special equipment.

Working in closed spaces
The WGBT index shown below assumes a situation without airflow and without sun or heat radiation. So it can be applied to situations in closed spaces. 
Working in the open air
The WBGT index assumes a situation with a light airflow and in the full sun or heat radiation. Comparable to a workplace outside, like a construction site. 

Below the activities identified on the basis of NEN-ISO 7243:1989
Heaviness workload Type of activities Max core temperature
Light workload:  Sitting comfortable: office work (writing, typing), working with light hand tools assembling, sorting), driving a car 
Standing: drilling, milling, sauntering (max speed 3.5 km/hour
max 29°C
Medium workload:  Continuous work with hand and arm: working with medium-heavy equipment, hooking up tractors, plasterwork, driving a truck, driving a tractor over unpaved terrain, pushing / pulling light carts, walking with a speed of 3.5 – 5.5 km/hour) max 26°C
Heavy workload:  Working intensively with arm and torso: carrying heavy materials, shoveling, sawing, chiseling, pushing / pulling heavily laden cart, walking with a speed of 5.5 - 7 km/hour) max 22°C
Very heavy workload:  Very intensive activity with high to maximum pace: shoveling heavy loads or digging, walking stairs, walking up a slope, walking with a speed of more than 7 km/hour max 18°C
 Source: FOD Werkgelegenheid, Arbeid en Sociaal Overleg


A lot has been written about work-related risks. However, with regard to heat in the workplace, as yet there is no concrete legislation. The Health and Safety Decision of May 1, 2018 contains no mandatory measures, but it does provide a guideline on which to base your measures.
Article 6 makes it clear that temperature must no damage people’s health. It is important to take the activities and the physical burden into account. 

If the temperature can no longer be regulated, the correct PPG has to be provided. In the cold, that helps, but in the heat, it often creates an addition burden. In that case, the time people work in the warm environment must be shortened or alternated with less burdensome activities. 

The FNV (a Dutch trade union organization) has developed a Heat Stress Calculator to make a global assessment of the risks. If there is heat in the workplace, that aspect has to be included in the RI&E. When determining which measures to take, use the advice of the company doctor or another expert.

Useful guidelines for offices
With regard to working in offices and workplaces, there are general rules: 
  • In case of temperatures about 26˚ C, there is an additional physical burden and it is important to think about measures. 
  • For light physical office work, there is a maximum temperature of 28˚ C.
  • For intensive physically demanding work, the maximum temperature is 26˚ C, provided there is a clearly noticeable airflow.
  • For very strenuous physical work, there is a maximum temperature of 25˚ C, provided there is a clearly noticeable airflow, otherwise the maximum temperature is 23˚ C.


We see that work-related heat stress is becoming an increasingly relevant subject. That is why we have studied this area in recent years, and we are the first consultancy in the Netherlands to provide solutions. Our PPG advisors have operated in various work environments. They are happy to share their experiences with you:


Cooling products

Our solution reduces the effects of heat exposure,


Who we are
VeiligGoed in a nutshell

Read more about our mission and services


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