Heat stress presents an increasingly significant challenge in Belgium and across Europe. Rising temperatures, increasingly demanding working conditions, and the widespread use of personal protective equipment (PPE) can cause workers to overheat more quickly than ever before. The consequences extend beyond discomfort and safety, because heat stress also has a significant impact on productivity, operational continuity, and overall business costs.

As specialists in personal protective equipment (PPE), we can provide a clear overview of what heat stress is, how to recognise it, the applicable legislation, and—most importantly—which solutions really work.

1. What is heat stress?

Heat stress is the physical strain placed on the body when it is unable to sufficiently regulate and dissipate excess heat. The body’s core temperature rises, which can lead to serious health risks. Symptoms such as fatigue, dizziness and difficulty in concentrating can start to occur at 38°C. In extreme situations, body temperature can rise above 40°C, which is life-threatening.

2. Effects of heat stress

1. Physiological effects

• Increased body temperature: Above 38°C, workers may experience fatigue, dizziness, and a noticeable decline in concentration and alertness.
• Dehydration: Excessive sweating leads to a loss of fluids and electrolytes. This can result in headaches, nausea, muscle cramps, and impaired cognitive function.
• Skin and sweat-related issues: Heat rash, skin irritation, and a burning sensation
• Cardiovascular strain: increase in heart rate to dissipate heat, particularly dangerous for individuals with pre-existing heart or vascular conditions

2. Acute heat-related conditions

• Heat cramps: Painful muscle spasms caused by the loss of salts and fluids
• Heat exhaustion: Characterised by weakness, dizziness, rapid heartbeat, nausea, and cold, clammy skin
• Heat shock/heat stroke: A medical emergency in which the body can no longer regulate its temperature. Core body temperature may exceed 40°C, requiring immediate medical attention.

3. Cognitive and mental effects

• Reduced concentration and alertness
• Slower reaction times
• Impaired decision-making
• Increased risk of errors and accidents

4. Productivity effects

• Reduced physical performance
• Increase in absenteeism and safety risks
• Need for longer or additional breaks

5. Long-term effects of chronic heat exposure

• Impaired thermoregulation: Over time, the body is no longer able to regulate its core temperature. This can result in less efficient perspiration and impaired blood flow to the skin.
• Increased risk of cardiovascular and kidney problems: The body attempts to cool down by increasing the heart rate and perspiring profusely (fluid loss), placing additional strain on the heart and kidneys.
• Chronic fatigue and reduced work capacity: A greater need for recovery breaks

3. When does heat stress occur?

Heat stress can result from multiple factors:

OR

Heat stress is rarely the result of one single factor. Key contributing factors include:

• Environmental factors: Exposure to direct sunlight, high ambient temperatures, high humidity levels, and insufficient ventilation
• Work factors: Physically demanding tasks, high workload, and long working hours
• PPE: Thick, multi-layered, or non breathable clothing—such as airtight protective suits
• Personal factors: age, fitness, hydration, medication, acclimatisation

4. The economic impact of heat stress

For employers, heat stress is not only a health and safety concern, but also a significant business risk.

• More accidents due to reduced alertness
• Lower productivity due to physical and mental exhaustion
• Higher absenteeism
• Financial impact due to errors, downtime and medical costs

5. Legislation on heat and thermal stress (Belgium & Netherlands)

5.1 Belgium: Codex on Wellbeing at Work

In Belgium, heat stress is governed by the regulations under thermal environmental factors.

Book V - Title 1: Thermal environmental factors

Chapter I - Risk analysis and preventive measures

Risk analysis (mandatory)

Employers are required to carry out a risk assessment covering all thermal environmental factors. This includes both climatic influences—such as solar radiation and outdoor temperatures—and technological sources, including heat generated by furnaces, machinery, or industrial processes.

The following factors must be taken into account:

• Air temperature
• Relative humidity
• Airflow rate
• Thermal radiation
• Physical workload
• Working methods and equipment used
• Availability and use of workwear and use of PPE
• Change of these factors throughout the working day

The assessment is not a one-time snapshot: interaction and variation of these factors over time ultimately determine the levels of risk.

Preventive measures (mandatory)

Based on the risk assessment, employers are required to implement appropriate preventive measures. These measures must:

• Be aligned with the identified risk factors
• Take into account action values for heat exposure
• Comply with general workplace comfort and wellbeing regulations

Examples: ventilation, breaks, adjusted working hours, cooling vests, drinking water, shade, technical interventions.

Mandatory provision of beverages

Codex - Section 8: Beverages (Art. III.1-63)

"Depending on the nature of the work and the associated risks, the employer must ensure that employees are provided with drinking water or another suitable beverage."

This means:

• Drinking water is mandatory in hot conditions
• A supply of drinking water must be easily accessible
• Individual cups must be available

Source: Federal Public Service Employment - Thermal environmental factors

5.2 The Netherlands: Working Conditions Decree (Article 6.1 - Physical factors)

In the Netherlands, the Working Conditions Decree (Arbowet / Arbobesluit) requires that workplace temperatures must not be harmful to the health of employees. While there are no fixed maximum temperature limits, employers are obligated to take measures to prevent health issues and heat-related harm.

When exposure to high temperatures cannot be avoided, employers must:

• Assess whether the work in high heat is necessary
• Limit the duration of exposure to heat
• Alternate hot work with cooler tasks
• Provide cool drinks
• Provide PPE

Source: Arbopo - Working in hot conditions

6. Organisational and technical measures for working with heat stress

Organisational measures

• Additional breaks
• Adjusted working hours
• Sufficient drinking water (legal requirement)
• Rotating shift systems

Technical measures

• Ventilation
• Shade
• Cooling

7. PPE solutions for working with heat stress

In addition to technical and organisational measures, appropriate personal protective equipment (PPE) can play a key role in preventing heat stress. The following is a comprehensive guide to selecting PPE when working with heat stress.

7.1 BREATHABLE AND PROTECTIVE WORKWEAR