Emergency response for heat and cold

When prevention fails, what happens in the first minutes often decides whether a worker recovers fully, suffers lasting harm or dies. This lesson describes how to respond to heat and cold emergencies at an awareness level. Every workplace must have the first aid attendants, supplies and procedures required by its province or territory or by the Canada Labour Code, and workers who may need to respond should take recognized first aid and CPR training. What this lesson adds is the planning: making sure that the equipment, procedures and people needed for heat and cold emergencies are in place before they are needed.

Principles for every emergency

A few principles apply to every heat or cold emergency. First, make the scene safe: a worker who has collapsed on a roof, in a trench, in a confined space or beside traffic may need to be moved, but rescuers must not become casualties themselves. Second, call for help early: emergency services should be called at once for any suspected heat stroke, moderate or severe hypothermia, deep frostbite, cold water immersion, or anyone who is unconscious, confused, having trouble breathing or not improving. Third, start treatment on site while waiting: for heat stroke, that means cooling; for hypothermia, that means preventing further heat loss and handling gently. Fourth, never leave an affected worker alone.

Every site should know its exact location for emergency calls, how long an ambulance takes to arrive, and how to guide responders to the worker. Remote sites, where help may be an hour or more away, need more on-site capability: trained first aiders, cooling and rewarming equipment, communication devices that work without cell coverage, and a transport plan.

Heat stroke: cool first, transport second

Heat stroke is the most time-critical thermal emergency. The extent of damage depends mostly on how long the core temperature stays above about 40 °C, so the priority is to cool the worker as quickly as possible, starting immediately, on site. Many sports medicine and military guidelines summarize this as cool first, transport second: when rapid cooling is available on site and medical help is present or on the way, cooling should not be delayed for transport. In a typical workplace, the practical approach is to call 911 immediately and cool aggressively while waiting for the ambulance, continuing cooling during transport if possible.

The most effective cooling method for exertional heat stroke is immersion of the body up to the neck in cold or iced water. Cold water immersion can lower core temperature at roughly 0.15 to 0.35 °C per minute, several times faster than other methods. Workplaces where heat stroke is a foreseeable risk, such as outdoor sites in hot weather, foundries and hazmat operations, can prepare for this with a large tub, a stock tank or a body cooling bag, or even a tarp held up at the edges and filled with water and ice, called the tarp-assisted cooling method. The worker's head must be kept above water and the person supported by at least two responders.

When immersion is not possible, use the next best methods together: move the worker to shade or an air-conditioned space, remove as much clothing and protective equipment as possible, soak the skin with cold water continuously while fanning vigorously, apply ice packs or cold wet towels to the neck, armpits and groin and, better still, cover as much of the body as possible with ice-water-soaked towels rotated every few minutes. A cold shower or hose can also be used. Ice packs on the neck, armpits and groin alone are much slower than immersion or whole-body soaking.

# Time to cool from 41.5 C to 39.0 C with different methods (approximate rates in C per minute)
start, target = 41.5, 39.0
methods = {
    "cold water immersion":         0.20,
    "rotating ice-water towels":    0.10,
    "spray and fan":                0.07,
    "ice packs at neck/armpit/groin": 0.03,
}
for m, rate in methods.items():
    minutes = (start - target) / rate
    print(f"{m:32s} about {minutes:5.1f} minutes")

cold water immersion             about  12.5 minutes
rotating ice-water towels        about  25.0 minutes
spray and fan                    about  35.7 minutes
ice packs at neck/armpit/groin   about  83.3 minutes

The difference is dramatic. Cold water immersion would bring the worker below 39 °C in roughly 12 minutes, while ice packs alone would take more than an hour, long after the window in which cooling is most protective. That is why workplaces with a foreseeable heat stroke risk should plan and stock for rapid whole-body cooling, not just a few ice packs in the first aid kit. Cooling is usually stopped at about 38.5 to 39 °C when a reliable temperature is available, to avoid overcooling, and medical personnel guide this; in the absence of a temperature reading, cooling continues until emergency responders take over or the worker clearly improves.

Do not give fluids by mouth to a worker who is confused, drowsy or vomiting, because they may choke. Do not give medications for fever such as acetaminophen or ibuprofen; they do not work for heat stroke and may harm the liver or kidneys. Watch breathing and be ready to place an unconscious worker in the recovery position and start CPR if they stop breathing normally.

Heat exhaustion and milder heat illness

For heat exhaustion, stop the work, move the worker to a cool place, loosen or remove heavy clothing and protective equipment, and cool them with cold water, wet cloths, fans and ice packs. If they are fully alert and not vomiting, give cool water or an electrolyte drink to sip. Have them lie down with legs raised if they feel faint. Stay with them and check them regularly. If they do not improve within 15 to 30 minutes, if they get worse, or if they become confused, treat as heat stroke and call 911.

For heat cramps, the worker should stop and rest in a cool place, drink water and eat a salty snack or drink an electrolyte drink, and gently stretch the affected muscle. For heat syncope, have the worker sit or lie down in a cool place and drink water slowly once fully alert; anyone who faints should be assessed, because fainting can also signal heat stroke or a heart problem. For heat rash, keep the skin cool and dry.

Workers who have had heat exhaustion or heat stroke should not return to work in heat that day, and workers who have had heat stroke need medical clearance and usually a gradual return with reacclimatization. Every heat illness should be reported and investigated so that the causes can be fixed.

Hypothermia

The response to hypothermia depends on its severity. For all stages, prevent further heat loss: get the person out of the wind, rain and cold, into a warm shelter or vehicle if possible, and insulate them from the ground. Remove wet clothing gently, cutting it off if necessary to avoid excessive movement, and replace it with dry clothing, blankets or a sleeping bag, covering the head and neck. A vapour barrier, such as a plastic sheet or emergency blanket, outside the insulation reduces evaporative and convective heat loss. A hypothermia wrap, sometimes called a burrito wrap, combines a ground pad, insulation and a vapour barrier.

For mild hypothermia, where the worker is shivering, alert and able to swallow, give warm, sweet drinks and high-energy food, which fuel shivering. Let the person rest in a warm place and rewarm gradually. Shivering is the body's own effective rewarming mechanism. The worker should not return to cold work that day and should be watched for worsening.

For moderate or severe hypothermia, where shivering has decreased or stopped, the person is confused, drowsy or unconscious, call 911 at once. Handle the person very gently and keep them horizontal, because a cold heart is prone to dangerous rhythms that rough movement can trigger. Do not let them walk or exercise. Do not give food or drink unless they are fully alert. Apply heat only to the trunk, such as warm packs or heating pads wrapped in cloth on the chest, armpits and back, never directly on skin, and never to the arms and legs, which can worsen afterdrop. Do not rub the limbs. Check breathing and pulse carefully for up to a minute, because they may be very slow and faint; if there are no signs of life, start CPR if trained and continue until help arrives. People with severe hypothermia have survived prolonged resuscitation, which is why responders say no one is dead until they are warm and dead.

Frostbite and other cold injuries

For frostbite, get the worker to a warm place, remove wet clothing and anything tight such as rings and watches, and protect the affected area. Do not rub frostbitten tissue, and never rub it with snow. Do not use direct high heat such as a heater, fire, heating pad or hot water bottle, because numb skin burns easily. Most importantly, do not thaw frozen tissue if there is any chance it will refreeze, for example if the worker must walk out through snow on frostbitten feet; refreezing causes much worse damage. If rewarming is appropriate, the recommended method is immersion in warm, not hot, water at about 37 to 39 °C until the skin becomes soft and colour returns, typically 15 to 30 minutes; this is painful, and medical care should follow. Do not break blisters. All but the most minor frostbite should be assessed by a health care provider.

Frostnip can be rewarmed by covering the area and holding it against warm skin, such as fingers in the armpits or a warm hand over a cheek, and it should recover fully. Trench foot is treated by gently drying and warming the feet, elevating them, and seeking medical care, as the injury can worsen after rewarming. Hypothermia takes priority over frostbite: treat the life-threatening condition first.

Cold water immersion

For a worker who has fallen into cold water, the priorities are to avoid becoming a second victim and to get the person out without delay. Reach or throw, do not go: use a pole, rope, ladder or throw bag from a secure position, and only trained rescuers with proper equipment should go onto ice or into the water. Once out, handle the person horizontally if possible, especially if they have been in the water for more than a few minutes, because blood pressure can drop dangerously when a person is lifted vertically after prolonged immersion. Treat for hypothermia and call 911. Anyone who has inhaled water, even if they seem fine, should be assessed because breathing problems can develop later.

Planning and equipment

Emergency response for thermal hazards depends on preparation. The heat and cold plans should identify who will respond, how they will be alerted, what equipment they will use and where it is kept, and how emergency services will be called and guided to the site. Practical items include:

Drills help. A five-minute practice run of setting up a tarp for ice-water cooling, or of packaging a person in a hypothermia wrap, makes it far more likely that a crew will act quickly and correctly in a real emergency. After any thermal emergency, the incident should be investigated: what happened, why the prevention measures did not work, and what will change.