Beating The Heat

"Two Firefighters Succumb to Heat" were the headlines of a newspaper article the day after a chemical spill at a loading dock. The firefighters were entry team partners of mine from our hazardous material response team when we responded to a spill of...

Hot weather saps energy so a consistent pace of work activity, at least slower than normal, will help to prevent heat stress. When it comes to hazmat response where personnel will work in chemical clothing many teams decrease the work duration period according to the heat stress. Quite often Level A attire utilizes one-hour capacity air bottles with the self-contained breathing apparatus (SCBA). While one-hour bottles provide up to 40 minutes of air duration while working many teams limit the on-air time to 20 minutes maximum for safety reasons. With this in mind heat stress situations would further decrease the maximum time in order to avoid undue heat related problems to the wearers of chemical clothing.

The following is an accepted guideline for decreasing on-air time in respect to the heat burden;

Source; National Fire Academy Hazardous Materials Site Practices, Hazardous Materials Strategies and Tactics by David M. Lesak

Hot weather could find teams limiting their personnel to 10 minutes while inside a suit. This limitation may require more responders to rotate entry and back-up assignments to complete strategic objectives. Finally, the NFA also recommends that entry personnel rest and rehabilitate for the following periods after an entry for a specified temperature.

4. Hydration

Monitor your Input
The intake of water is critical in response to heat stress, not only before being in the heat but also during an activity. Since the human body is largely made up of water good hydration must be maintained to perform critical bodily functions. Drink plenty of water and often is the key! The National Institute of Safety and Health (NIOSH) recommends ingesting up to 16 ounces of water before a heat inducing activity and then 8 ounces every 20 to 30 minutes during the activity to maintain good hydration. Do not depend on thirst to indicate when fluids should be taken; at the point of feeling thirsty a person is already playing catch-up. Water is best, especially for short duration activities, but sports drinks can assist with rehydration. Sports drinks, as a result of their ingredients, are critical for long duration activities that last more than 60 to 90 minutes.

Avoid fluids that contain alcohol and caffeine as they are diuretics and can cause depletion of water through the kidneys. Also avoid carbonation because it can cause gastric distress and inhibit the absorption of water in the intestines. Fruit juices or drinks high in sugar and carbohydrates can also prevent the absorption of water in the body. Research has indicated that a lightly salted and low carbohydrate solution is best at rehydrating the body. The Gatorade Sports Science Institute indicates the ideal rehydration drink would be one that has about 6% or 14 grams of carbohydrate per 8 ounces, a blend of sucrose, glucose, or fructose for flavor, approximately 100-110 milligrams of sodium, and no caffeine or carbonation. Obviously, in the absence of a sport drink water will be adequate.

One last precaution with fluid intake is that too much water can be ingested and cause a problem known as hyponatremia. While more common in log distance runners and cyclists this condition lowers the blood sodium levels and can lead to heart malfunctions.

Monitor your Output
A well hydrated person will urinate often and the color of the urine should be straw colored or light yellow. A dehydrated person may not urinate for several hours and the urine will most likely be deep yellow in color. If this is the case hydration needs to be increased. The dehydrated person is also at extreme risk of a heat related illness if called upon for emergency service. Drinking proper fluids should be undertaken immediately. In extreme cases IV's may be the best and fastest course of action to rehydrate a person. Personnel who have recently consumed alcoholic beverages are prime candidates for heat related problems as alcohol is a diuretic. Alcohol consumption stimulates the kidneys to produce urine and this body fluid loss can produce a 3% loss of body weight within four hours of ingestion. The resulting dehydration has a negative effect on performance and endurance and greatly increases the risk of heat illness. Personnel should notify team leaders if their personal hydration is a question.

5. Engineering Controls

The last line of defense to prevent heat stress problems with personnel is with engineering controls. These are outside of the body devices that assist with the cooling process. They include;