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Hydration Strategies for Firefighters

Joe Domitrovich, Physiologist/Firefighter Health,
and
Brian Sharkey, Physiologist/Firefighter Health

Wildland firefighting is arduous work. Shifts are long, often on steep terrain and at higher elevations. The weather is usually hot and dry, and the fire increases exposure to heat. When hard work is performed in a hot environment, blood is sent to the skin to cool the body, primarily through evaporation of sweat (figure 1). Sweat is a combination of water and electrolytes.

Figure 1—The evaporation of sweat cools our bodies.

As sweating continues, often at a rate of more than 1 liter per hour, the body loses a lot of fluid. The heart and circulatory function and the ability to work can be affected. If fluids are not replaced, the process that regulates body temperature begins to fail. Work becomes impossible and the possibility of life-threatening heat stroke increases dramatically.

Studies of wildland firefighters indicate that fire suppression activities generate about 7.5 calories of heat for each minute worked, more than 400 calories an hour. Additional heat (about 180 calories per hour) comes from the environment and the fire.

Complete evaporation of 1 liter of sweat removes 580 calories of heat. That means a firefighter needs to evaporate about 1 liter (1.06 quarts) of sweat for each hour of hard work.

These fluids must be replaced. The U.S. Army and the American College of Sports Medicine recommend that you consume 1 liter of fluid every hour of hard work to maintain blood volume and to enhance your ability to lose heat by sweating. That means drinking (figure 2) before, during, and after work.

Maintaining hydration requires that firefighters understand their own fluid loss. Water and electrolytes must be properly replaced, for example with water and sports drinks. Consumption of too little water can lead to dehydration while consumption of far too much water can lead to serious illness or death.

Figure 2—Wildland firefighters should drink 1 liter of
fluid for every hour of hard work.

Personal Drinking Systems

Water bottles have been a fixture on firelines since they replaced canteens. However, sipping hydration systems (figure 3) have become more common as companies produce models appropriate for wildland firefighters and their line gear. During the 2006 fire season, the Missoula Technology and Development Center (MTDC) and the University of Montana (UM) Human Performance Laboratory conducted a field study comparing water bottles and sipping hydration systems. Firefighters using the two systems showed no differences in hydration status or work output. The benefits and drawbacks listed in table 1 were mentioned by firefighters during the study.

Figure 3—A typical sipping
hydration system.

Cleaning Strategies

An MTDC-UM study of the general sanitary conditions of wildland firefighters' personal drinking systems found that most sipping hydration systems had never been cleaned. Over time, the insides of water bottles and the reservoirs and drinking tubes (figure 4) of sipping hydration systems develop a microbial film. The addition of sports drinks increases the likelihood that a microbial film will form. The microbial film is not necessarily hazardous, but it is likely to give the water an unpleasant taste. The microbes in this film have the potential to cause allergic responses or illness. Firefighters' drinking systems should be cleaned regularly to prevent problems.

Figure 4—The tubes of sipping hydration systems can
develop a microbial film if they are not cleaned regularly.

Soaps and Tablets

Dish soap or mild bleach solution can be used to clean personal drinking systems. Bleach could shorten the life of the system and may leave an unpleasant taste.

Studies have evaluated the effectiveness of chlorine dioxide water purification tablets for cleaning a sipping hydration system's reservoir and drinking tube. After 4 hours of cleaning, studies showed that the microbial level dropped below detectable levels. The tablets do not require the system to be flushed after cleaning because the tablets create potable water.

Camelbak (http://www.camelbak.com) also has cleaning tablets that generate chlorine dioxide. The tablets are soaked in the system for 5 minutes. Then the system is rinsed and dried.

Cleaning Kits

Cleaning kits by Camelbak use a different approach. These kits include brushes and frames. The brushes are used to scrub the walls of drinking systems, especially harder to reach areas, such as the tubes in sipping hydration systems. The frames allow the reservoir to dry out more quickly after use and cleaning.

MTDC Recommendations

To maintain hydration:

• Firefighters may use water bottles, a sipping hydration system, or a combination of both. Studies showed no differences in hydration status based on the personal drinking system firefighters used.
  
  
• Firefighters should drink small amounts of fluid every 15 to 20 minutes. About one-third to one-half of the fluid consumed during each shift should be a sports drink.
  
  
• Firefighters may benefit from a combination of personal drinking systems, using water bottles for sports drinks (figure 5) and sipping hydration systems for water. Do not use sports drinks in hydration systems because of difficulty in cleaning the tubes.

Figure 5—About one-third to one-half of the fluid
firefighters consume should be sports drinks that
provide electrolytes and carbohydrates.

• Firefighters should rinse personal drinking systems after each use and clean them after each assignment.
  
  
• Firefighters should not share water bottles except during emergencies.
  
  
• Firefighters should monitor their hydration status during an assignment by paying attention to:
  • Urine color—Pale yellow or wheat color is normal. A lighter color is a sign of overhydration. Dark yellow or brown urine is a sign of dehydration.
    
    
  • Body weight—You should not lose more than 2 percent of your body weight during an assignment.

For additional information on hydration, consult the MTDC report "Fitness and Work Capacity: 2008 Edition" (0851–2815–MTDC) to be published late in 2009.

About the Authors

Joe Domitrovich is an exercise physiologist at MTDC. His work includes hydration, nutrition, employee health, stress, and fitness testing. Domitrovich also is a wildland firefighter. He received a bachelor's degree in kinesiology at Cal Poly San Luis Obispo in California and a master's degree in exercise physiology at the University of Montana, where he is completing an interdisciplinary studies Ph.D. with an emphasis in exercise science.

Brian Sharkey, an exercise physiologist at MTDC, has done research and development work on fitness tests and programs, heat stress, hydration, nutrition, protective clothing, tools, fatigue, work/rest cycles, and employee health (wellness). His work has been honored with USDA Superior Service and Distinguished Service Awards, and a Forest Service Technology Transfer Award. He is past president of the American College of Sports Medicine and author of several books, including "Hard Work," with coauthor Dr. Paul Davis, published by Human Kinetics in 2008.

Additional single copies of this document may be ordered from:

USDA Forest Service
Missoula Technology and Development Center
5785 Hwy. 10 West
Missoula, MT 59808–9361
Phone: 406–329–3978
Fax: 406–329–3719
E-mail: wo_mtdc_pubs@fs.fed.us

Electronic copies of MTDC's documents are available on the Internet at:

http://www.fs.fed.us/eng/t-d.php

For additional information about hydration strategies, contact Joe Domitrovich at MTDC:

Phone: 406–829–6809
Fax: 406–329–3719
E-mail: jdomitrovich@fs.fed.us

Forest Service and Bureau of Land Management employees can search a more complete collection of MTDC's documents, CDs, DVDs, and videos on their internal computer networks at:

http://fsweb.mtdc.wo.fs.fed.us/search/

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USDA Forest Service, Technology and Development Last Modified: 03/30/2013 03:06:32