Heat Stress in the Workplace

By Terrence Thomas, CRSP, OSSE Technical Advisor

The human body normally operates at an internal temperature of between 36° and 38° C. It also has an amazing ability to discharge excess heat from the body by increasing blood flow to the skin and sweating.

However many factors including air temperature, humidity, air flow, physical activity, clothing and personal factors can impede this ability to keep body temperature from exceeding the safe range, resulting in heat stress.

The American Conference of Governmental Industrial Hygienists (ACGIH) defines heat stress as “the net heat load to which a worker may be exposed from the combined contributions of metabolic cost of work, environmental factors (i.e., air temperature, humidity, air movement, and radiant heat) and clothing requirements.”

Metabolic cost of work considers issues such as body heat produced chemical processes, exercise, hormone activity, digestion, etc. while clothing requirements consider what a worker is wearing (light, loose clothing, heavy work uniform, impervious clothing).

Employers in food/beverage processing or general manufacturing need to be aware of the potential risk of workplace heat stress. The employer should be able to identify situations where heat stress may be present and implement steps to control the situation. There are only short periods each year where outdoor heat stress can be an issue in BC, however the potential for indoor heat stress can extend year round in certain situations.

Examples of food processing workplaces that could face indoor heat stress situations include bakeries, breweries, candy/chocolate manufacturers and coffee/tea processors. General manufacturing workplaces could include foundries, smelters, roofing product manufacturing and fibreglass insulation manufacturing. The examples provided are not an inclusive list but employers should have the ability to determine the heat stress level at any given time.

Part 7, Division 4, regulations 7.26 – 7.32 of the WorkSafeBC Occupation Health & Safety Regulation (OHSR) spell out the legal responsibilities regarding heat exposure while the accompanying guidelines provide further information to allow employers to comply with the requirements.

Regulation 7.27 states the regulations apply to a workplace if
(a) a worker is or may be exposed to thermal conditions which could cause heat stress,
(b) the thermal conditions could result in a worker’s core body temperature exceeding 38°C (100°F)
(c) the thermal conditions are in excess of the levels listed in the screening criteria for heat stress exposure in the heat stress and strain section of the ACGIH standard for un-acclimatized workers.

Regulation 7.29 requires that if a worker is or may be exposed to the conditions in section 7.27 the employer must
(a) conduct a heat stress assessment to determine the potential for hazardous exposure of workers, using measures and methods acceptable to the Board, and
(b) develop and implement a heat stress exposure control plan meeting the requirements of section 5.54(2)

The Exposure Control Plan must contain the following elements;
(a) a statement of purpose and responsibilities;
(b) identification, assessment and control;
(c) education and training;
(d) written work procedures, when required;
(e) hygiene facilities and decontamination procedures, when required;
(f) health monitoring, when required;
(g) documentation, when required.

Identifying Heat Stress

Heat stress illnesses range from heat rash which is normally a minor health issue through heat cramps, then heat exhaustion and finally heat stroke which is a major life threatening illness which requires immediate medical attention.

Heat Stroke is a life threatening condition that requires immediate transportation to a medical facility. Symptoms include headache, confusion, hot flushed skin and lack of sweating.

Heat Exhaustion symptoms include nausea, headache, excessive sweating and cool, clammy skin. Treatment consists of removing to cooler environment, providing water and cool compresses. Evaluation by a medical professional is required if heat exhaustion is suspected.

Heat Cramps are muscle pains caused loss of fluids and body salts due to excessive sweating. Treatment includes moving to cooler environment and maintaining proper hydration while active.

Heat Rash is caused when sweat is trapped against the skin by clothing causing red pimples looking like blisters to appear. Treatment includes moving to cooler, dryer environment and keeping skin