How often is a heat stress survey required?

A survey is required where the risk assessment shows employees may be exposed at or above the 30 °C WBGT limit. It is repeated at the frequency the assessment sets, and at least every 24 months. The risk assessment is redone at least every 24 months, and sooner after an incident or a change in the work. Plan a new one if yours was done under the Environmental Regulations for Workplaces, 1987, which were repealed on 6 September 2026.

Does a heat stress survey need an approved inspection authority?

No. The Physical Agents Regulations, 2024 call for a competent person with knowledge, training, experience and qualifications relevant to heat stress. Monitoring must follow SANS 7243 (regulation 10), with instruments calibrated to a traceable national or international standard (regulation 7).

When should the survey be done, and what should we prepare?

Plan it for the hottest part of the shift and the hottest time of the year, with production running normally. Have your risk assessment, shift and work-rest schedules, and a list of the clothing worn in hot areas ready.

HEAT STRESS ASSESSMENT & SURVEY

A heat stress assessment shows whether employees working near furnaces, ovens and hot processes, or outdoors, reach the legal action level or limit for heat stress. Under the Physical Agents Regulations, 2024, your risk assessment should cover heat wherever such work takes place, as well as in poorly ventilated buildings.

Heat stress is the total heat load on the body. It comes from the work rate, the environment and the clothing worn, so air temperature alone does not show the risk. We measure the wet-bulb globe temperature (WBGT) index at the work positions and take account of workload and clothing. Exposure is then compared with the 27 °C action level and the 30 °C limit.

REACH OUT

Worker cutting steel with an angle grinder as sparks fly

WHY HEAT STRESS MATTERS

Heat stress can cause heat rash, heat cramps and heat exhaustion, and in severe cases dizziness, collapse or heat stroke. It also reduces concentration and causes fatigue, which raise the accident risk and lower productivity. The business sees the cost in absenteeism and health-related incidents.

Some employees are at greater risk because of age, health or medication. Others are not yet acclimatised, such as people new to the job or back from leave. Clothing adds to the load. Table 9 of the regulations sets clothing adjustment values that are added to the WBGT: 3 for double-layer woven clothing, such as coveralls over work clothes, and 11 for single-layer vapour-barrier coveralls with a hood.

Heat stress falls under the Physical Agents Regulations, 2024, made under the Occupational Health and Safety Act, 1993 (OHS Act). The assessment and testing duties are:

• Risk assessment (regulation 6): a competent person must assess exposure to physical agents before it starts, then at least every 24 months. The assessment covers heat, cold, lighting, indoor air quality, vibration and non-ionising radiation.
• Heat stress survey (regulations 7 and 10): by a competent person where the risk assessment shows exposure may reach the 30 °C WBGT limit, at the interval it sets and at least every 24 months.
• Controls (regulation 17): cooling and other physical agent controls must be inspected and tested by a competent person at least every 24 months.

The regulations do not require an approved inspection authority (AIA) for any of this work. Review your occupational health risk assessment under section 8(2)(d) of the OHS Act together with the results. Our free online Compliance Gap Assessment shows which assessments your workplace needs and which are overdue.

Interior of a large industrial warehouse with overhead cranes

WHAT THE LAW REQUIRES FOR HEAT STRESS

Foundry workers in protective gear pouring molten metal

HOW WE CONDUCT A HEAT STRESS SURVEY

Christo de Wet leads every heat stress survey. He is an occupational hygienist registered with the Southern African Institute for Occupational Hygiene (SAIOH), ROH 0953, with 15 years of experience.

Before the visit, we review your physical agent risk assessment and agree on the tasks, work positions and shifts to cover. The limit applies over 1 hour, so we plan measurements for the hottest part of the shift. Where possible, we also choose the hottest time of the year.

On the day, we measure the WBGT index according to SANS 7243 at each work position, with calibrated instruments, while production runs normally. For each task, we record the work rate, the clothing worn and the work-rest pattern, because each one changes the heat load. Afterwards, we compare exposure with the action level and limit, and set out practical controls in order of priority.

We also work on mines and quarries, on surface operations only, under the Mine Health and Safety Act, 1996. There, Christo can take the section 12(1) appointment for those operations. We are based in Pretoria, work in all nine provinces and are a B-BBEE Level 2 contributor.