Hypothermia is one of many risks we face during cold-weather ops
Winter brings a unique set of risks and challenges for firefighters ranging from mild inconvenience to extreme danger. In this article I’ll focus on severe cold when it becomes very difficult and risky to conduct basic fire service operations.
Experience has proven that serious fires are more likely to occur during periods of severe cold often resulting from the continual use of heating systems as well as temporary and innovative heat sources. The colder it gets the greater the probability that it will become a long-duration exterior defensive operation. Cold-weather firefighting is sometimes reduced to a battle of endurance.
The impact on firefighter health and safety increases with the deviation from “normal conditions” whether the actual temperature bottoms out at 0 degrees F on the Gulf Coast or -40 degrees F on the windswept prairies. A temperature of 10 degrees F (-12 degrees C) would be an extreme weather emergency in many areas and a cause for celebration in others. When temperatures dip well below freezing the risk factors faced on the fire-ground increase.
Severe cold create extreme challenges for both firefighters and their equipment. The risk of hypothermia is an obvious concern particularly when operations must be conducted outdoors. The personal protective equipment (PPE) approved for structural firefighting is designed to protect the user from the heat of a fire. In theory the insulating layers incorporated into structural firefighting ensembles should be equally effective at keeping the user warm in a cold environment; however PPE provides only limited insulation from severe cold.
In many cases firefighters need protection from both heat and cold at the same incident although generally not at the same time. They’re exposed to the cold while responding and setting up then they may encounter extreme heat while conducting an interior fire attack. And then they have to deal with the cold again when they leave the fire environment for rehab.
Multiple cycles of hot and cold present a serious challenge to firefighters and their equipment. A firefighter who must go back into the fire environment after rehab and air cylinder replacement is likely to encounter SCBA problems as well as rapid fatigue. Whenever possible the incident commander should send fresh crews inside to continue the attack.
We generally don’t plan to spend a long time in an active fire environment but we may spend hours exposed to extreme cold. There is a relatively narrow body temperature range in which a firefighter can work safely and efficiently inside their PPE. If the internal body temperature deviates more than a few degrees from normal up or down important physiological processes become dangerously unbalanced. The predictable results include fatigue heat stress and burns or hypothermia frostbite and exhaustion.
There’s no easy solution to the problem of dressing appropriately during cold-weather ops. The protective clothing that keeps us from getting burned for a few seconds in a flashover will keep us warm for a few minutes on a very cold day but not for several hours. Adding layers of clothing to provide extra insulation from the cold also adds weight and bulk restricting mobility and requiring additional physical effort to perform simple tasks. Firefighters who are dressed for the cold are likely to become fatigued and it’s not unusual for a firefighter to be drenched in sweat on the inside and covered with ice on the outside.
That extra weight and bulk creates even greater problems if the firefighter is called upon to engage in interior fire suppression operations. The firefighter who dressed to stay warm outdoors is likely to be at risk of heat stress inside a building because of extra warmth and weight. When the overheated firefighter goes outside to rehab and change air cylinders the situation reverses almost instantaneously from hyperthermia to potential hypothermia. Wet skin and perspiration-soaked inner layers of clothing create an even greater risk from exposure to extreme cold.
Unfortunately although we understand the problems associated with extreme cold we have very few options when it comes to solving them. Firefighters who work in areas that experience extreme cold generally wear additional layers of clothing beneath their PPE to endure exterior operations. In so doing they understand that their ability to conduct interior fire suppression operations will be compromised.
Note: Firefighters must be aware of the thermal characteristics of the materials they’re wearing under their protective clothing. Some synthetic materials used in modern thermal underwear are extremely effective in maintaining body temperature but shouldn’t be worn in situations where exposure to high temperatures is a risk. Tip: Natural fibers and thermally stable blends may generally be worn in contact with the skin.
Fire chiefs must ensure that special preparations are initiated for predicted periods of unusual cold. This begins with ensuring that every firefighter is dressed to stay as warm as possible without compromising protection. Many fire departments issue two complete sets of PPE to their members to avoid the risk of responding in turnouts that are already wet from a previous incident. Wet clothing should be replaced at the first opportunity including every layer down to the thermal underwear.
Work cycles for firefighters must be shortened in proportion to the temperature and exacerbating considerations such as wind chill. If prolonged operations are required additional personnel should be summoned to replace members who’ve been exposed to extreme cold particularly if they’re wet. Ideally the members who are replaced should go to back to a firehouse or an indoor facility where they can remove wet clothing and bring their body temperatures back up to the normal range. A complete change of clothing is a better option than trying to quickly dry and reuse the same items.
If rehab must be conducted at the incident scene the rehab area should be inside a building vehicle or enclosure that provides relief from the cold and members must not return to work wearing wet clothing. Portable heaters are helpful in some situations; however they can only provide temporary relief from extreme cold.
Warm food and liquids are an important component of winter rehab. The food is needed to restore energy that has been consumed performing tasks that would be much less demanding under normal conditions. Warm food and liquids deliver warmth to the body just as cold drinks help to cool firefighters who have elevated temperatures.
Winter operations present a long list of additional safety concerns including the danger of slipping on icy surfaces and having to dig through snow banks to reach buried hydrants. Even smoke and fire behavior change when there’s an extreme differential between indoor and outdoor temperatures requiring adjustments in strategy and tactics.
Like it or not cold temperatures combined with hot fire aren’t going away. Our best strategy: to plan and prepare for the inevitable and then plan to be on vacation in a warmer climate when the inevitable occurs.