Too hot to work?

We are currently experiencing a rise in temperatures. It is crucial to ensure that this does not become a detrimental situation for your workers, particularly if they are required to engage in physical exertion. What considerations should you take into account to safeguard the well-being of your workers? What preventive measures should you implement?

Risk Analysis

According to the Occupational Health and Safety Code, every employer is required to conduct a risk analysis of thermal environments in the workplace, regardless of whether these environments are influenced by technological or climatic factors, and whether they result in excessively hot or cold working conditions.

In conducting this analysis, you must consider the combination of the following factors:

• temperature, relative humidity, and air velocity;
• thermal radiation;
• physical workload;
• methods and equipment used;
• work clothing and personal protective equipment.

Excessive Heat?

The legislator has established action values for heat exposure, which are measured using the WBGT index. When these action values are exceeded, workers may be at risk of adverse health effects, commonly referred to as thermal stress. The action values vary depending on the level of physical workload.

If the values are exceeded, preventive measures must be implemented.

Indicative examples of physical workload:

• Very light work: secretarial tasks
• Light work: manual tasks at a table
• Moderate work: standing tasks
• Heavy work: earthworks.

The WBGT Index

To accurately measure these temperatures, a simple thermometer is insufficient. A specific warm temperature can be intolerable in very humid conditions, while it may not pose a health risk in dry conditions. Therefore, humidity must be considered, and in some instances, wind speed and direct radiation from the sun or technological sources (e.g., an oven) must also be taken into account.

The WBGT index is measured using a "wet bulb globe" thermometer. The WBGT - 'Wet Bulb Globe Temperature' - is an index derived from three measured temperatures:

• the dry air temperature,
• the radiation temperature,
• and the wet temperature.

The calculation varies depending on whether the workstation is indoors or outdoors, particularly in the presence of solar radiation.

If you do not possess such a device, you can find guidance on this link  regarding how to determine the WBGT using a simple thermometer in conjunction with a hygrometer.

However, these values are rarely exceeded in shaded workplaces where light work is performed, such as offices. While these workplaces do not present an immediate risk of thermal stress, the conditions may not be comfortable, and the heat can adversely affect workers' concentration and productivity. For these environments, reference should be made to an applicable comfort standard for moderate temperatures, specifically the EN ISO 7730 standard. Thermal comfort is defined as an individual's satisfaction with the thermal conditions of their environment. It is referred to as thermal comfort when the individual does not wish to be either warmer or cooler. For more information.

NBN EN ISO 7730 standard "Ergonomics of thermal environments: analytical determination and interpretation of thermal comfort by calculating PMV and PPD indices and by local thermal comfort criteria".

Preventive Measures to Implement in Cases of Excessive Climatic Heat

If the action values (WBGT) are exceeded, you must, in accordance with legislation, take the following measures to prevent thermal stress:

• provide refreshing drinks free of charge;
• provide protective equipment (shade screens, headgear, sunscreen, etc.) for workers exposed to direct solar radiation.

If the temperature exceedance persists for a period of 48 hours, you must ensure to:

• install an artificial ventilation system;
• grant additional rest periods.

To ensure thermal comfort for your workers during the hot summer months, you should aim to limit complaints regarding heat in the workplace to no more than 10%. This can be achieved by maintaining the so-called "PMV" index below 0.5, in accordance with the EN ISO 7730 standard. This index is determined based on air temperature, radiation temperature, relative humidity, air velocity, clothing insulation value, and the activity level of employees.

To accurately determine this index, specific measuring devices are required; however, for seated employees wearing light clothing, in our Belgian climate, this often corresponds to a target temperature between 24 and 26°C (normal air temperature).

During a very hot period, a temporary exceedance for a limited portion of the workday (maximum 10%) is still acceptable. Be sure to consider the points of attention below:

• To minimise heat from radiation, use blinds (preferably positioned outside the building).
• Avoid setting the air conditioning temperature too low (maximum 6°C lower than the outside temperature) to prevent large temperature differences and drafts.
• Adjust clothing (uniforms) to ensure they are light and made from sufficiently moisture-permeable fabrics.
• If possible, adjust work schedules to avoid the hottest part of the day. For example, you may ask your workers to start earlier or finish later. For more information on adjusting your schedules, click here.
• Encourage workers to stay hydrated by drinking sufficient water (preferably caffeine-free or unsweetened beverages) and provide facilities to keep drinks cool. 

Ozone and Workers Working Outdoors

It is important to note that during periods of high heat, high concentrations of ozone are common. The legislation regarding well-being does not include provisions concerning exposure to ozone of climatic origin. However, it should be regarded as a risk against which preventive measures should be taken. Certain individuals are particularly sensitive, including pregnant women, the elderly, and those with respiratory or cardiovascular conditions.

As the concentration of ozone is lower indoors than outdoors, greater attention should be given to workers who are working outside. Among the measures that can be implemented are:

• conducting physically demanding work only in the morning when ozone concentrations are at their lowest;
• performing lighter tasks to reduce the volume of breathing and the dose of inhaled ozone;
• providing rest periods indoors.

You can refer to the forecasts from the Interregional Environment Cell (CELINE – www.irceline.be) to determine when to implement these measures. 

What Can Securex Do for You?

If you require further information on the measures to take in response to high heat, please consult your occupational doctor.

If you wish to conduct a WBGT measurement, please contact your external service for prevention and protection at work at the following address: health-safety@securex.be.