Heat Stress

Heat stress is a term used to describe the stress placed onto the human body due to persistent exposure to high levels of heat. This includes all types of heat, including air temperature and humidity, exposure to radiative heat (e.g. sunlight, process/equipment heat), and internally produced heat (i.e. exertion). Exposing a person to heat stress causes their body temperature to increase, and to self-cool they will begin to sweat. The longer that a person is exposed to heat stress, the longer they will be sweating, losing fluids and salts. As this continues, the person will become dehydrated, and their body will be less able to effectively self-cool, and their body temperature will rise. Rising body temperatures, if not managed, will result in potentially serious heat-related illnesses.

If you have questions or concerns about heat stress, contact BCIT HSE.

BCIT Employees are also encouraged to review any content and resources available on the BCIT HSE SharePoint.

Heat stress can result in several heat-related illnesses that can be very severe. A common misconception is that these illnesses are progressive, in that a person experiencing heat stress will first show a less-severe illness, and will experience progressively more severe illness as the heat stress progresses. A person can experience any one or all of these illness with prolonged heat stress, the presence or absence of one illness does not mean that another will or will not occur.

Heat rash

Skin irritation due to excessive sweating, typically due to hot and humid weather, high levels of physical activity, etc. Symptoms are clusters of red pimples or small blisters, usually on neck, upper chest, groin, under breasts, and in elbow creases.

Heat cramps

Powerful muscle cramps that occur due to dehydration from excessive sweating. The main symptoms are painful cramps or spasms in muscles of the arms, legs, and/or abdomen. Note: Heat cramps can be a symptom of heat exhaustion.

Heat exhaustion

Heat exhaustion describes the bodies response to the excessive loss of fluids and salt, generally from excessive sweating. Symptoms:

Heat stroke

Heat stroke is the illness that occurs when the body can no longer control its own temperature, and the body temperature has risen rapidly (i.e. hyperthermia). If not treated quickly, it can cause permanent disability or death. Symptoms include:

Confusion, altered mental status, slurred speech, or total loss of consciousness.
Very high body temperature.
Profuse sweating, or evidence that sweating has ceased. In dry climates, hot, dry skin.
Seizures

In general, the following are steps to take for any heat-related illness. However, the more extensive first aid measures apply more to the more serious conditions (heat stroke and heat exhaustion).

Cool the affected person: Move them to shade/away from heat sources, remove any unnecessary clothing layers (including shoes and socks), cool body with cold water (baths with heat stroke, cold wet cloths or ice applied to head, neck, armpits, groin; soaking clothes with cold water).
Provide cool water to drink, with frequent sipping. For heat cramps you can also recommend a sports drink or include heating a
Contact BCIT First Aid ((604) 451-6856): have them come to you. Do not hesitate to call 911 if you feel it necessary.
Notify your instructor/supervisor.

When convenient, report any heat-related illness developed during BCIT activities through IRIS if you are a BCIT employee, or to your instructor if you are a student.

There are several risk factors that can contribute experiencing heat stress and experiencing a heat-related illness.

Environmental risk factors

Air temperature and humidity: Air temperature is an obvious important indicator of heat, however for how humans perceive heat, air humidity is equally important. When looking at the weather to determine heat, humidex (i.e. “feels like”) is the value you should examine, as it factors both temperature and humidity. In general, we recommend implementing heat stress control measures when the humidex will exceed 30.
Direct Radiative Heat: This refers to heat coming directly from a source in the form of infrared radiation. Radiative heat will directly apply heat to a person regardless of air temperature. The most common source is sunlight, although there can be other sources such as equipment (e.g engines, boilers, etc.) or processes (e.g. hot water, steam, etc.).
Indirect Radiative Heat: Materials can interact with radiative heat in ways that can cause the material to be a heat source, when it normally would not produce any heat. Reflective or lightly pigmented surfaces (e.g. metals, concrete, etc.) can reflect radiative heat, while dark surfaces (e.g. asphalt, tar, etc.) can absorb and release radiative heat. Therefore, the area where a person is can contribute to heat stress (ex. A person outdoors in sunlight on a asphalt surface would be experiencing more heat than another person outdoors in sunlight on a grassy surface; the asphalt absorbs and release heat).

Activity-based risk factors

Exertion: The level of exertion required for an activity will influence heat stress. A by-product of physical exertion is increased metabolic activity, and therefore internally generated heat. The higher the exertion level, the more heat a person will generate within themselves.
Clothing/PPE: Clothing and equipment can contribute to the level of heat experienced. Heaviness of clothing and breathability are both important factors.
Activity Duration/Rest Periods: Related to exertion; the duration of an activity and the frequency and the duration of rest periods are important for level of heat stress.

Biological factors

Things like overall fitness, body weight, health conditions, and other personal factors can influence your tolerance to heat, as well as simple individual differences in heat tolerance. People are able to become acclimatized to heat, meaning that they are more able to tolerate higher heat levels without placing strain on their body as quickly as a non-acclimatized person. Acclimatization typically takes 10-14 days working in a hot environment to develop, and will dissipate after around 7 days working in a less hot environment. Therefore, it can be an unreliable factor to consider when considering the level of risk with activities in a hot environment.

Departments and program areas should have measures they can put into effect to help reduce the risk, however some general guidance you can use include:

All activities

Have a team/class meeting to talk about the heat hazard and control measures being put in place, as outlined further below.

Low exertion activities (e.g. office work, low intensity walking, arm moving)

Promote wearing loose, breathable clothing, and taking frequent water breaks.
Where possible set up fans for air movement.
Keep doors and windows open to allow for cross breezes.
Reorganize activities so that higher strain activities happen at cooler parts of the day (mornings)

Moderate and high exertion activities (e.g. trades work, manual labour, walking and carrying)

In addition to the low-exertion activity recommendations:

Limit higher exertion activities during hottest periods of the day, and implement a work-rest schedule (50% rest during moderate exertion, 80% rest for high exertion).
Communicate to employees and students:
- Do not be pressured to work faster or harder to meet deadlines, make sure that breaks are taken.
- Stop working and report to your supervisor/instructor if you think you are over-heating.
If available, workers can be provided with cooling vests if they need to work during hot periods of the day.

Outdoor work considerations

Ensure workers/students have access to shade and/or cooling areas, and encourage regular cooling breaks.
Limit amount of work in direct sunlight, or on surfaces that radiate heat (asphalt, concrete, etc.) during hot periods of the day.
Ensure workers/students have plenty of water, and/or access to a water station.