Heat disorders are caused by prolonged exposure to hot temperatures or excessive physical activity, restricted fluid intake, or failure of the body's ability to regulate its temperature. The general term used for heat disorders is hyperthermia.

Heat becomes a problem when humidity, air temperature, and radiant heat combine with hard work to raise body temperature beyond safe limits. Sweat is your main defense. Everyone on the fireline must understand the importance of drinking water often.

There are several terms and types of heat related illnesses which can include heat cramps, heat exhaustion and heat stroke:

Heat cramps are the least serious form of hyperthermia. They are the first sign that the body is having difficulty with increased temperature. Heat cramps are a warning sign that more serious problems may soon develop.

• Painful muscle spasm, often in the abdomen, back as well as extremities
• Fatigue
• Thirst 

Heat exhaustion is more serious than heat cramps. Heat exhaustion results when the body produces more heat than it can dissipate. Inadequate fluid intake can be a major contributing factor. The body may become dehydrated, or its temperature regulation system may begin to fail. 

• Weakness
• Extreme fatigue
• Nausea
• Headaches
• Wet, clammy skin
• Dark yellow or orange urine

Prompt treatment of heat cramps and heat exhaustion is usually successful. Patients recover in a matter of hours or, at most, a day, or two. Heat Stroke poses more serious problems.

Heat stroke is a medical emergency. Heat stroke is caused by failure of the body’s heat controls.  Whereas heat cramps and heat exhaustion may be treated locally, heat stroke patients should be medevac’d off the line immediately, by air if possible, as their condition may worsen suddenly.

The main characteristic is altered mental status or confusion.

• Mental confusion
• Loss of consciousness
• Seizures
• Elevated body temperature (sometimes higher than 105.8) 

The presence or absence of sweating is NOT a criterion for heat stroke.  50% of Heat Stroke victims are still sweating.

Brain damage and death may result if treatment is delayed.

The first steps in treating any form of hyperthermia include:

• Place in cool shaded environment
• Remove excess clothing and equipment
• Cool with fanning and/or water dousing
• Rehydrate orally with cool water only if conscious and can follow directions
  • Provide liquids which contain electrolytes, i.e. Gatorade, etc.
• Transport to an emergency facility if recovery is not prompt.
• Individual is not to go back to work that day.
• If symptoms persist following 10-15 minutes of treatment, suspect heat stroke, and begin more aggressive cooling therapy and immediate transport to an emergency facility.

You can prevent the serious consequences of heat disorders by improving your level of fitness and becoming acclimated to the heat. Maintaining a high level of aerobic fitness is one of the best ways to protect against heat stress. The fit worker has a well-developed circulatory system and increased blood volume. Both are important to regulate body temperature. Fit workers start to sweat sooner, so they work with a lower heart rate and body temperature. They adjust to the heat twice as fast as the unfit worker.