Managing the consequences of heat in the workplace: the importance of using the right metrics

The perceived heat: a factor often underestimated

Last week, many of us felt a lot of discomfort on terraces, in factories, offices, construction sites, and homes, to the point that any effort became painful, even dangerous. Yet, the thermometer did not break records. So what happened? Humidity was unusually high.

What truly impacts health, well-being, and safety at work is the perceived heat, a measure that a simple thermometer cannot quantify alone. We need an index that takes into account the humidity level in the air, such as the Humidex, an index expressed in °C, combining air temperature and humidity level. Introduced for the first time in 1965, the current formula for the Humidex was developed in 1979 by the Canadian Meteorological Service.

Concrete Examples of Extreme Heat

For example, on July 30 at noon, near Tours, the temperature in the shade was 34.2°C with a humidity level of 69%, resulting in a Humidex (or perceived heat) of 49.5°C. Near Poitiers, with a temperature of 34.4°C, the Humidex reached 48°C. In early afternoon in Sarthe, the perceived temperature climbed to 50.2°C, and a large part of northwestern France experienced perceived temperatures well above 40°C. The next day was just as unbearable, but by the third day, the situation started to improve.

The Impact of Heat on Productivity and Health

The impact of high temperatures on health is well documented, including the report Work and Health-Environment: what challenges to face regarding disruptions? or the report Work and Climate: how to address the impact of climate on health at work?

At work, productivity starts to drop as soon as the temperature exceeds 24°C and falls by half above 30°C. Furthermore, heat causes fatigue, decreased alertness, drowsiness, and accidents.

The risk thresholds of the Humidex:

Below 29°C: Comfort zone
30-34°C: Perceived discomfort
35-39°C: Marked discomfort
40-54°C: Serious health risk
Above 54°C: Deadly danger

Anticipating Climate Challenges with the Climate Performance Diagnosis

This episode lasted only a few days, but it allowed everyone to assess its impact on their activity. With climate change, such episodes will multiply and intensify, though not everywhere in the same way or at the same pace.
The Climate Performance Diagnosis (DPC) from Tardigrade AI is a tool that provides each site with a set of historical and projected risk metrics for each climate peril. For the heat peril, the DPC offers numerous risk measures, from the Humidex to the number of hot days, including heatwave index, or the evolution of air conditioning needs, so that every company, regardless of its sector, has actionable and relevant information to understand and anticipate.

Resilience through Anticipation

Anticipation is key: the DPC not only allows decision-makers to access the year-by-year evolution of all climate risk metrics, following the chosen IPCC greenhouse gas reduction scenario. Anticipation is the foundation of resilience, and the DPC is the best tool to build an adaptation strategy.

FAQ: Essential Questions about Heat in the Workplace

What is the Humidex and why is it more relevant than a simple temperature measurement?

The Humidex is an index that combines air temperature and humidity level to determine the heat actually felt by the human body. It is more relevant than a simple temperature measurement because our body is particularly sensitive to humidity which impacts our ability to regulate our internal temperature through sweating.

At what value of Humidex should measures be taken in the workplace?

Preventive measures should be taken as soon as the Humidex exceeds 35°C (marked discomfort). Above 40°C, concrete actions must be implemented to protect the health of employees.

How will climate change affect heat episodes in the future?

With climate change, intense heat episodes will become more frequent, longer, and more intense. The peculiarity is that these changes will vary significantly by region, highlighting the importance of having localized projections.

What are the main consequences of excessive heat on productivity?

Productivity significantly decreases with heat: a reduction of 50% beyond 30°C, an increase in errors, decreased concentration, slowing of cognitive and physical processes, and an increased risk of workplace accidents.

How can the Climate Performance Diagnosis (DPC) concretely help my business?

The DPC provides precise and localized data on the evolution of climate risks for your sites. For heat, it allows you to anticipate air conditioning needs, adapt work schedules, plan investments in thermal insulation, and develop appropriate protocols to protect your employees.

Are there legal obligations concerning heat in the workplace?

In France, although there is no specific legal maximum temperature, employers have a general obligation to ensure the safety and protect the health of workers. Official recommendations are issued during heatwave episodes, and labor inspections may intervene if conditions are deemed dangerous.