With hot weather forecast across Northern Ireland, the Health and Safety Executive for Northern Ireland has reminded employers that there is no law setting a maximum workplace temperature or defining when it is too hot to work.

Instead, employers have a legal duty to ensure the welfare of their employees. This duty centres on the concept of thermal comfort, which is how acceptable a person finds the temperature in their environment.

Thermal comfort is shaped by environmental factors such as sources of heat and humidity, as well as personal factors including the type of clothing worn and the physical demands of the work.

The simplest way to judge whether a workplace is thermally comfortable is to ask the employees or their representatives. The regulator says that at least 80 percent of workers must be satisfied with the thermal environment. If satisfaction falls below that level, the employer is expected to take corrective action.

Measuring air temperature alone may not give a full picture, because high humidity or physically strenuous tasks can still make conditions uncomfortable even if the thermometer reading seems acceptable.

Exposure to extreme heat can lead to discomfort, dehydration and exhaustion, the HSENI warns. These symptoms can reduce productivity and increase sickness absence.

The regulator advises employers to monitor thermal comfort as temperatures rise and to take steps to protect staff welfare, even without a fixed statutory upper limit.