Measuring heat stress

The guidance is aimed primarily at employers, managers, occupational health professionals and safety personnel. The objective is to provide a systematic approach to the decisions required to minimise or reduce the risk of heat stress in your workforce. Employees will also find the information useful in understanding why their employer is taking this approach.

Is heat stress a problem in your workplace?

Unless someone collapses from heat exhaustion, the possible health effects of working in the heat may not be obvious. This means it requires employers to identify whether those employees who may be at risk from heat stress are suffering from any heat-related illnesses. In some situations this may have to be treated with sensitivity, eg sustained heat exposure may result in symptom reporting not readily associated with heat exposure, eg rashes, impaired male fertility etc.

You can use information you will already have to hand to identify individuals who may be at risk, for example:

• look for patterns in absenteeism, types of illnesses and their frequency of occurrence, the nature of employee complaints, etc. Take particular note of where employees work, their job, how experienced they are, whether any illnesses are recurring etc
• read through any RIDDOR reports and any internal accident or injury reports. Are there any patterns to the nature of reportable accidents or injuries? Could any repeated accidents be attributed to the effects of heat, eg fatigue, loss of concentration etc?
• speak to employees, their safety representatives (eg unions), to managers in other companies that are involved in the same business as your organisation, contact industry federations or associations etc
• undertake observations of the workplace and record those observations. HSE has a heat stress check list that is free to download from our website which may assist you in assessing your heat stress risk

Talking about heat stress

When explaining to your employees what heat stress is remember that this is a two-way street and it is important to listen to what all your employees tell you about heat stress. This helps engage everyone in dealing with heat stress risks. For example, those involved with purchasing personal protective equipment need to be aware that while it can protect against one risk it can contribute to the causes of heat stress.

After you have identified the problems and put forward solutions then, as an employer, you should ensure that individuals carrying out any measurements or implementing methods of managing the risk are trained and fully competent.

Measuring heat stress

Measuring heat stress can be complex - you may need help from an occupational health professional to measure heat stress in your workplace. This may involve:

• measuring the heat stress an individual is exposed to (eg by using a technique such as the wet bulb globe temperature index, see BS EN 27243)
• estimating metabolic rate (see BS 8966)
• measuring heart rate
• estimating clothing insulation values (see BS ISO 9920)
• if other alternatives cannot be implemented you may consider physiological monitoring (see ISO 9886)