Tuesday, July 10, 2012

Work Place Heat Hazard

Hot environments in a wide range of industries present serious hazards to employee safety and health.  Heat stress, the combination of  heat, humidity and physical labor, can lead to serious illness and even death.


Long exposure to extreme heat or too much activity under a hot sun causes excessive perspiration, which can lead to heat exhaustion.  Symptoms include headache and a feeling of weakness and dizziness accompanied by nausea and vomiting, there may also be cramps.

In heat exhaustion there is excessive perspiration.  By contrast, in heat stroke, there is an absence of perspiration; an extremely high body temperature; hot, dry skin; confusion; and loss of consciousness and/or convulsions.  An extremely high body temperature can cause death.

Treatment for heat exhaustion includes:
  • Move the person to a cool environment (i.e. a well-ventilated or shaded area).
  • Remove or loosen their clothing.
  • Increase the consumption of fluids.  (Do not force an unconscious person to drink.)
For heat stroke or if the person is unconscious:
  • Reduce the body’s temperature as rapidly as possible via a cool water or sponge bath; fan the body surface.
  • Contact a physician immediately.

Case Study:  Restaurant Industry

In July of 2006, MIOSHA received an employee complaint regarding heat stress in a restaurant.  The complaint alleged that employees were working in 95-degree temperatures, they felt dehydrated, the temperature may have affected an employee’s breathing, an employee was sent to the emergency room for heat exhaustion, and the conditions were unworkable.

Investigation Background

While there are no MIOSHA regulations requiring temperatures to be kept under a certain degree, Section 11(a) of Act 154 (the General Duty Clause) requires the employer to furnish to each employee, employment and a place of employment which is free from recognized hazards that are causing, or are likely to cause, death or serious physical harm to the employee.

Work operations involving high air temperatures, radiant heat sources, high humidity, and strenuous physical work activities have a high potential for inducing heat stress in employees engaged in such operations.  The work operations identified in this investigation involved employees cooking at a grill in the kitchen, chefs cooking in the dining room, and workers dishwashing in the kitchen of a restaurant.  Employees had developed and experienced heat-induced disorders such as heat exhaustion, fainting and heat fatigue, for approximately two weeks prior to the investigation.

Investigation Measurements

During the investigation wet bulb globe temperature (WBGT) measurements were obtained.  WBGT offers a useful, first-order index of the environmental contribution to heat stress; it is influenced by air temperature, radiant heat and humidity, but does not account for all the interactions between an employee and the environment.

During the investigation the WBGT measurements indicated employees were exposed to readings ranging from 77.9 to 96.3 °F on July 28, 2006, and from 82.4 to 93.2 °F on August 2, 2006.  It was noted there were outdoor record high temperature of 96 °F on
July 31, 2006, and 97 °F on August 1, 2006.

Heat Stress Violations

The investigation of employee exposure to heat stress in this workplace resulted in a citation of the General Duty Clause being issued, based on known industry standards.

The American Conference of Governmental Industrial Hygienists (ACGIH®) provides general controls to deal with heat stress from air temperature, as well as the interactions between employees and the environment.  The interactions below were investigated during the inspection.

Heat reduction – During the investigation it was noted that employees were exposed to radiant heat during the cooking process and were exposed to steam while dishwashing.  The employer had not provided shielding, the ventilation above the dishwasher designed for removal of steam was not functioning, and cooling garments and portable air chillers were not utilized.

An employer should shield employees from radiant heat sources, and reduce process heat and water-vapor release.  Cooling garments (vests, bandanas) can be worn to reduce the heat exposure to employees and portable air chillers can be used. 

Ventilation – During the investigation it was noted that air conditioning was provided in the dining room and office areas, but there was no air conditioning supplied to the kitchen area for cooking and dishwashing.  It was also noted that the air conditioning in the dining room was not functioning at the time of the inspection.  Circulating fans were used in the kitchen areas; however, it was not effective since air that exceeds 95 °F can increase the heat load on the body.

An employer should provide general air movement through use of supply and exhaust ventilation.

Administrative controls – During the investigation it was noted that breaks were not taken by employees according to the ACGIH® recommendations for frequency found in Table 2 of the Heat Stress section of the Threshold Limit Values (TLV) booklet.  Employees were not allowed sufficient recovery time for heat exposure.  Breaks that were taken by dishwashers and dining room chefs were taken outdoors in a hot environment, not in a cool area.

An employer should set acceptable exposure times to heat, should allow sufficient recovery for employees exposed to heat, and should limit physiological strain by reducing heavy activity.  As metabolic rate increases from work demand, an employee’s exposure to heat stress can result in an excessive heart rate and elevated body core temperature by not allowing for proper recovery from heat exposure for the body.

Training – During the investigation it was noted that employees were not trained on the signs of symptoms of heat stress and were not permitted to practice self limitation to exposure.

Employers should train employees and supervisors by providing accurate verbal and written instructions about heat stress, including self-determination of exposures.  Employees should be aware of the signs and symptoms of heat stress and should be encouraged to detect these signs in themselves and in coworkers.  Employees should also be permitted to practice self limitation of heat exposure based on these signs.

Heat stress hygiene practices – During the investigation it was noted that most employees did drink water, but were not monitored or encouraged to drink cool water every 20 minutes.  Additionally, aside from the clothing worn by dishwashers, employees were required to wear uniforms that through fabric and style (high collars, neckties, and chef’s hats) limited evaporation.

Employers should encourage fluid replacement and the use of proper clothing.  Employees should drink small volumes (approximately 1 cup) of cool liquid every 20 minutes.  Free movement of cool, dry air over the skin’s surface maximizes heat removal through evaporation of sweat from the skin; water-vapor-impermeable or thermally insulated clothing restricts heat removal.

Medical surveillance – The investigation revealed the employer did not screen employees to identify those employees more susceptible to heat.

Employers should allow pre-placement screening to identify those employees susceptible to systemic heat injury.  Employees who take medications that may compromise normal cardiovascular, blood pressure, body temperature regulation, renal or sweat gland functions; and those employees who abuse alcohol, may have an increased susceptibility to heat stress.  Employers can also encourage healthy life styles and ideal body weight.

Acclimatization – During the investigation it was noted the employees were acclimated to the heat exposure.

Acclimatization is a gradual physiological adaptation that improves an individual’s ability to tolerate heat stress.  Full-heat acclimatization requires up to three weeks of continued physical activity under heat-stress conditions similar to those anticipated for the work, with a loss occurring after four days.  Employers can develop a plan to expose employees to heat at gradually increasing rate over a five-day period. 

Company Abatement

The employer submitted the information below as actions taken to address the issue:

  • Air conditioning equipment in restaurant was repaired.
  • Cooling vests and cooling bandanas were purchased for employees.
  • Temperature monitoring control devices were purchased and place in the kitchen and dining room.
  • A temperature monitoring and tracking procedure was implemented.
  • Management attended a MIOSHA safety in the workplace seminar.
  • Signs were posted educating the staff about heat stress and how to recognize the symptoms in themselves and others.
  • Employees were given access to cool beverages.
  • Major renovations of the building which would include replacing HVAC equipment were planned.
CET Division Services

If you have any questions on heat stress, or need a workplace evaluation, please call the MIOSHA Consultation Education and Training (CET) Division at 517.322.1809. 
Additional information and handouts can be obtained from www.michigan.gov/mioshawww.osha.gov; and www.cdc.gov/niosh/topics/heatstress.

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