Working in extreme temperatures isn't just something that happens to outdoor workers. Those who work indoors can also be exposed to temperature extremes that could lead to heat or cold stress.

Indoor facilities that can get dangerously hot include:

  • Iron and steel foundries
  • Boiler rooms
  • Bakeries and commercial kitchens
  • Laundry facilities
  • Brick-firing and ceramic plants
  • Chemical plants
  • Material handling and distribution warehouses

These all have a few things in common: they tend to be operations that involve high air temperatures, radiant heat sources, direct contact with hot objects, and strenuous physical activity.

Cold temperatures can be a concern for those who work in food preparation (such as airline catering), cold storage facilities, and transportation of cold or refrigerated goods. Some of these employees will spend the majority of their shifts in cold rooms, where temperatures can dip to the freezing mark.

In this article, we'll lay out the risks of working in very hot or cold indoor environments and provide some suggestions for keeping workers safe.

The Risks of Extreme Indoor Temperatures

As mentioned above, there are two key risks posed by extreme temperatures: heat stress and cold stress.

Heat Stress

Heat stress is really a blanket term for a collection of heat-related illnesses, the most serious of which is heat stroke. Heat stroke sets in when the body is no longer able to regulate its core temperature. If a worker isn't given immediate attention, heat stroke can be fatal. Other symptoms include confusion, loss of consciousness, seizures, and sometimes a lack of sweating (learn 7 Lesser-Known Factors That Contributes to Heat Stress).

While heat stroke is the most serious consequence of heat stress, heat rash is perhaps the most common. While it may not be as serious as other heat-related illnesses, it can create plenty of discomfort and disrupt an employee's ability to carry out their work.

Heat stress can also take the form of heat cramps or heat exhaustion, which is often accompanied by a headache, nausea, dizziness, weakness, irritability, thirst, and heavy sweating.

Cold Stress

Cold-related illnesses and injuries are broadly referred to as "cold stress." Extreme cold puts a great deal of stress on the body, since it requires more energy to keep the internal core temperature up.

For indoor workers, the most pressing concern is hypothermia. This sets in when the body loses heat faster than it can replace it and the core temperature drops below 95 degrees. Workers with mild hypothermia remain alert but may begin to shiver, have pale and cold skin, and stomp their feet to generate heat. As it progresses and the body temperature continues to fall, the shivering stops. Workers experiencing moderate or severe hypothermia can lose coordination, become confused or disoriented, have trouble standing or walking, have a slower pulse and dilated pupils, and even lose consciousness. For this reason, it’s important to address signs of mild hypothermia immediately – allowing the illness to progress can endanger a worker’s life.

How to Control Indoor Temperature Hazards

There are three ways that employers can help control extreme temperature hazards:

  • Engineering controls
  • Administrative controls
  • Protective clothing

Engineering Controls

Your first line of defense against extreme heat and cold should be engineering controls – methods built into the design of plants, equipment, or processes to mitigate hazards.

There are numerous options for protecting indoor workers from exposure to excessive heat, including:

  • Automating and mechanizing tasks to reduce physical labor, which in turn reduces the amount of heat produced by the body
  • Reducing radiant heat emission by covering hot surfaces with materials like aluminum
  • Insulating hot surfaces to reduce heat exchange between the heat source and the work environment
  • Installing reflective or absorbent shields to prevent radiated heat from reaching work stations
  • Installing vents or air conditioning to maintain a comfortable atmosphere

Engineering controls for cold indoor work environments include:

  • Using radiant heaters to warm employee work areas
  • Installing shields to reduce drafts and condensation
  • Using insulating materials on equipment handles
  • Making sure equipment and machines can be operated without removing gloves
  • Minimizing air velocity (applicable particularly in refrigeration rooms)

Administrative Controls

Once engineering controls are in place, look at what administrative controls (changes in work procedures) you can enact to protect workers from extreme temperature hazards.

Potential administrative controls for hot environments include:

  • Allowing workers to acclimate to the hot environment before assigning a full workload
  • Spacing heat generating processes a good distance apart
  • Mandating frequent breaks
  • Providing cool rest and break areas with plenty of cool water to drink
  • Allowing workers to set their own work pace, where possible
  • Educating workers on the signs of symptoms of heat stress
  • Training workers on the engineering controls, work practices, and clothing necessary to prevent heat-related illnesses and injuries

Administrative controls for cold work environments include:

  • Mandating frequent breaks
  • Providing warm, sweetened liquids to workers during breaks
  • Assigning workers to tasks in pairs to monitor each other for cold stress symptoms
  • Allowing workers to acclimate to working in a cold environment by gradually increasing the workload
  • Minimizing tasks that require fine manual dexterity or the removal of gloves
  • Regularly assessing job demands and have monitoring and control strategies in place
  • Avoiding assigning workers sitting or standing tasks for prolonged periods
  • Educating workers on the signs and symptoms of cold stress
  • Training workers on the engineering controls, work practices, and clothing necessary to prevent cold-related illnesses and injuries

Protective Clothing

Clothing has a major impact on how well workers can tolerate hot or cold temperatures.

Workers in hot environments should wear lightweight clothing that allows sweat to evaporate but stops radiant heat. In extreme conditions, workers might consider using protective clothing with cooling features, like vests equipped with cooling packs.

Workers in cold environments should dress in at least three layers of loose-fitting clothing to provide sufficient insulation. Ideally, they will wear an inner layer capable of wicking moisture, an insulating middle layer (preferably made of wool or synthetic fabrics), and an outer layer that provides ventilation to prevent overheating. Insulated gloves are essential, and some workers may opt for insulated boots, depending on the workplace (learn how to Manage Cold Stress with the Proper Winter PPE).

Note that any clothing worn by workers to deal with the heat or the cold must not compromise the protective qualities of their PPE.