Managing heat stress in the workplace

In hot workplace environments such as manufacturing or extractive processes where heat is added to the environment, heat stress can be an occupational workplace concern. Australia’s hot climate can also exacerbate extreme heat condition for some workers.

According to the American Conference of Governmental Industrial Hygienists, a worker’s core temperature needs to be below 38°C to prevent heat stress effects. To put this figure in real terms, when core temperatures reach 40°C, a person can have symptoms such as: seizures, loss of consciousness or, worse still, death.

Heat stress was recently put under the spotlight at a food manufacturing site as some of its employees who worked near hot ovens were experiencing heat exhaustion symptoms such as headaches. The business decided its occupational responsibility was to perform heat stress monitoring to determine a solution.

A personal heat stress device was worn by an employee for half the shift and exceedances were recorded by the monitor. For an accurate prediction of an employee’s body core temperature, a personal monitor is the best method to apply, as an earpiece records the wearer’s personal temperature in real time.

During the monitoring period, the air temperature of the working conditions varied according to the work being performed. Normally the air temperature is 32°C, which may be bearable or equal to a hot Australian summer’s day. But, when the employee was exposed to the oven area of operations, the air temperature was raised an additional 5°C to 37°C, and this resulted in increasing the employee’s core temperature 2°C. The elevated body response was due to the operator’s movement as well as the personal body’s response to heat, producing a core temperature of 38.8°C for the employee.

In order to determine a solution to heat stress in a workplace, factors that should be considered include clothing, personal fitness, metabolic energy or personal core temperature, category of work practices, work break allocation and ambient temperature. All these factors can influence the core temperature.

In hot occupational workplace conditions, engineering controls can be implemented and should be the first heat stress reduction step before the use of PPE. Controls which can greatly improve a workplace’s ambient environment include:

• introducing spot coolers, which can be directed to operating areas;
• improving heat barriers surrounding the heat source, which will prevent hot spots that can cause a sudden jump in an employee’s core temperature;
• installing an extractor system, which will release hot air outside and replace it with cooler ambient air;
• applying a cooling system to the whole area, which is the ultimate solution to eliminate temperatures that could cause heat stress.

PPE such as face shields and cooling vests should also be encouraged and can be worn to prevent a core temperature exceedance which occurs at 38°C.

Implementing procedures for 15-minute breaks every hour in an enclosed air-conditioned space nearby can also greatly reduce the risk of workers experiencing heat stress.

Other occupational workplace procedural additions that could help include:

• intermittent health checks on heart rate, fitness and medicine use (ensuring employee privacy is maintained);
• staff training on heat exposure and the importance of rehydrating and complying to heat stress PPE practices; and,
• supervisors to complete a staff heat exposure management practice to record shift ambient temperatures between lines, to ensure staff have no health complaints and are wearing additional heat stress PPE when working in hot environments, such as near the ovens in the example above.

Workplace environments ideally should be kept to 28°C temperature for a moderate work load or work rate category during the shift. Moderate work rate is typically 300 calories per hour used by the body’s metabolism.

Heat stress is an important occupational exposure to monitor and prevent, especially in Australia.

Samantha Sims is an Occupational Hygiene Consultant at Occupational Matters. The business aims to reduce occupational health exposure effects in Australia’s industry. Its consultants provide advice in occupational hygiene contaminant exposure monitoring over all industries. It specialises in using scientific gas detectors, air sampling personal pumps, noise sound level meters, surface swabs and other hygiene sampling instruments.

With 11 years’ experience, Sims has been performing assessments in the industrial hygiene field for industries such as quarries, mining, manufacturing, schools, offices, hospital/medical facilities, chemical and food manufacturing, printing/ink and paint production, metal fabrication and extraction industries.

Image credit: ©iStockphoto.com/Terry J Alcorn