Heat Illness Prevention & Sun Safety

Heat-Related Illness Prevention

Last Updated: January 07, 2019
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If you have additional questions, please contact the APHC Injury Prevention
Program at:

Email Address: usarmy.apg.medcom-aphc.mbx.injuryprevention@mail.mil
Telephone: 410-436-4655      DSN: 584-4655



1. Heat illness is a threat to individual health and to military operational success:

  • Despite well documented and effective techniques for preventing heat illnesses, they continue to be a threat to Soldiers in training and combat.

Each year an average of 2-3 Soldiers have died from heat stroke and more than 1000 Soldiers have developed a heat-related illness that required medical attention and/or lost duty time.

Even mild heat illness and dehydration can significantly degrade performance:  

  • Degrades performance
  • Losing 4% of body weight from dehydration degrades physical performance 50%
  • This 4% body weight loss is possible in less than 2 hrs!
  • Increases core body temp
  • Every 1% loss of body weight increases core temp .10-.23°C or .18-.40°F (increasing risk of more serious heat illness)

2. Heat illness is preventable!

  • The best solution to heat illness and dehydration related problems is prevention!

3. Training is required!


TYPES OF HEAT ILLNESSES                                                                                   

Exertional Heat Illness ("EHI") refers to a spectrum of disorders (e.g., cramps, heat exhaustion, heat injury, heat stroke) resulting from total body heat stress.  While there is a range of adverse effects that can result from the body over-heating, the 3 major heat illnesses are: heat exhaustion (can be milder or more severe), exertional heat stroke and hyponatremia.

HEAT EXHAUSTION                                                                                                                                       

“Canaries in the coal mine” - identify possible heat casualties early before they progress to severe types of heat illness - catch early as they need rest/water/evaluation and possible medical care.


  • Dizziness
  • Headache
  • Nausea
  • Weakness
  • Clumsy/unsteady walk
  • Muscle cramps


  • Rest Soldier in shade
  • Loosen uniform/remove head gear
  • Have Soldier drink 2 quarts of water over 1 hour
  • Evacuate if no improvement in 30 minutes, or if Soldier's condition worsens

HEAT STROKE                                                                                                                                      

Medical emergency – these cases already have abnormal brain function and can be fatal – initiate rapid cooling and EVAC!


  • Profuse sweating
  • Convulsions and chills
  • Vomiting
  • Confusion, mumbling - ask mental status check questions to see if brain is working correctly
  • Combative
  • Passing out (unconscious)


  • COOL and CALL!! – the faster the body is cooled, the less damage to the brain and organs
  • Remove all outer clothing
  • Initiate rapid cooling (iced sheets)
    • Cover all but face with iced sheets.
    • Ensure the iced sheet is soaked prior to applying to the casualty.
    • Fan the entire body.
  • Call for evacuation
  • Continue cooling during transport
  • NOTE: The same person should observe the Soldier during cooling and evacuation in order to spot symptom changes.


HYPONATREMIA "Water Intoxication"                                                                                     

This is a Medical Emergency – EVAC immediately, symptoms can be mistaken for heat exhaustion, though treatment is very different.  NOTE: condition most often occurs in TRADOC IET units, especially during BCT/OSUT.


  • Mental status changes
  • Repeated vomiting
  • History of consumption of large volume of water
  • Poor food intake
  • Abdomen distended/bloated
  • Large amounts of clear urine (if urine)


  • Do not give more water or IV!  If awake, allow Soldier to consume salty foods or snacks
  • Evacuate immediately

REACTING TO A HEAT ILLNESS CASUALTY:                                                      

Remember "M.A.D.E. in the Shade":

MOVE victim to cool location (e.g., shade, A/C car, building)

ASSESS victim to determine type of EHI

  • Signs/symptoms
  • Hydration (550 cord) to check for hyponatremia
  • Risk level (red beads or risk factors)
  • Mental status (for heat stroke)
  • Designate single person to continue monitoring. It is critical that a specific person is assigned to STAY with victim and continuously monitor all changes including mental status – Even the slightest changes that can occur in minutes may not be noticed if different personnel are checking victim – these slight changes can be critical in ensuring the best outcome for the victim.

DECIDE which EHI and take proper management approach

  • Heat Exhaustion: rest in shade, rehydrate
  • Heat Stroke: begin rapid cooling, evacuate immediately
  • Hyponatremia: evacuate immediately

EVALUATE other Soldiers and adjust training as necessary

WET BULB GLOBE TEMPERATURE                                                                      

Wet Bulb Globe Temperature (WBGT) is a composite temperature used to estimate the effect of temperature, humidity, wind speed, and solar radiation (e.g., sunlight). The WBGT index was developed in 1956 by the United States Marine Corps at Parris Island to reduce heat stress injuries in recruits. It is determined with special equipment and calculated to reflect components of air, humidity and wind that affect ‘actual temperature’ experienced by personnel: WBGT is calculated with the formula: 0.7Tw + 0.2Tg + 0.1Td

     Tw = Natural wet-bulb temperature (with dry-bulb temperature indicates humidity)

     Tg = Globe thermometer temperature (also known as black globe thermometer)

     Td = Dry-bulb temperature (actual air temperature)

Wet Bulb Globe Temperature (WBGT) Categories




Flag color


< 82

< 27.8















=> 90

=> 32.2


Ø Add 5°F for rucksack or body armor

Ø Add 10°F if in MOPP 4

RISK FACTORS FOR HEAT ILLNESS                                                                     


     - Higher temperature

     - High humidity (WBGT)



     - High exertion

     - Heavy loads/gear

     - Repeated strenuous days


Lack of Acclimatization: Acclimatization requires aerobic exercise in a warm environment. The body needs to adjust to environmental heat stressors prior to high exertion activities; simply being outside doing normal activities is not sufficient.

     NOTE: Hot weather is a key risk factor for heat injuries, HOWEVER:

     --> Heat illnesses can occur under green flag temperature conditions due to previous days' conditions and dehydration.  20% of all heat                illnesses occur outside of the 'heat season' and occur year-round.


Individual Risk Factors to EHI:

     - Poor fitness (2 mile run > 16 mins)

     - Body mass index (BMI) > 26

     - Age > 40

     - Gender (female)

     - Minor illness

     - Medication: Antihistamines (e.g., Benadryl, Atarax, CTM), decongestants (e.g., Sudafed); certain high blood pressure medications (e.g.,           diuretics, beta blockers); psychiatric drugs (e.g., tricyclic antidepressants, antipsychotics). NOTE: There is currently NO scientific                     evidence that caffeine use contributes to dehydration in habitual caffeine users or that it affects body temperature regulation.

     - Alcohol in the past 24 hours

     - Prior heat injury

     - Skin rash, sunburn, or poison ivy

     - Blood donation (< 3 days)

     - Sleep deprived

     - Highly motivated - the desire to meet or exceed standards may lead some Soldiers to continue to push themselves as early                               signs/symptoms of EHI occur. These Soldiers should not be discouraged from pushing themselves but cadre should be aware of their           tendency so that they can be watched more closely.



1. IDENTIFY THE HAZARDS:                                                                                                     

Know the Wet Bulb Globe Temperature (WBGT)

Know the Total Body Heat Stress = heat stress is the product of heat generated by the body (due to metabolism and activity) and heat gained from the environment minus heat lost in the environment.  Individual factors, clothing, equipment and activity level all need to be considered.

Know the Risk Factors for EHI.  Most commonly thought of risk factors are the temperature and the level of physical activity/exertion, however there are numerous individual risk factors to be aware of - especially consider when a single individual has more than one of the listed risk factors.

2. ASSESS HAZARDS:                                                                                                   

Utilize the WBGT temperature index

                    - Add 5°F for rucksack or body armor

                    - Add 10°F if in MOPP 4

Know your Soldiers - Identify individuals at increased risk

Monitor hydration status - Assess morning and evening as well as during training

Factor in previous days' conditions & activities - Consider temperature, activity levels, illnesses

Use a risk management matrix to document and manage decisions


          H   Heat category past 3 days

          E   Exertion level past 3 days

          A   Acclimation/other individual risk factors

          T   Time (length of exposure and recovery time)

3. DEVELOP CONTROLS:                                                                 

Plan in advance:

          - Estimate heat risk level 1 day prior

          - Consider:

                    Previous 2 days of heat exposure & Predicted Heat Category for that day

                    Training events (distance, pace, breaks, etc.) and Work-rest cycle, hydration guidelines, etc.


                    Location, Time of day

          - Adjust activity distances, durations, pace, and loads

                    Conduct high-intensity training in cooler morning hours

          - Ensure proper resources at appropriate locations

                    Functional WBGTs


                    Ice sheets (in cooler filled 1/3 water, 2/3 ice)

                    Medical: resources, locations, communication systems

Establish SOPs, train, and test Soldiers:

- Heat Illness prevention and Hydration cards and sunscreen to all

          - Place Heat Illness Prevention posters and urine guides in bathrooms, bulletin boards, DFAC, training areas, etc.

Identify how to monitor hydration & high risk personnel

Prepare communication capabilities, water, food/snacks, medical, and evacuation support:

                    - For most Soldiers, meals in garrison and MREs contain enough electrolytes so that consumption of commercial electrolyte                              beverages is not necessary.  However, Soldiers my choose to consume these products if they so desire.

                    - Ensure water control points throughout designated training areas.

                    - Ensure canteens/hydration packs are properly cleaned daily (FM 21-10).  Use of hydration packs is not recommended with                               commercial electrolyte beverages due to the risk of bacterial growth and contamination.

          - Pre-plan changes if METT-TC/Heat Category changes or if heat casualties occur


4. IMPLEMENT CONTROLS:                                                                                                            

Monitor Hydration and Personnel

          - Identify High risk personnel

          - Buddy system: Assign Low risk personnel to High risk personnel

          - Track individual hydration status

  •           Use parachute 550 cord or Ogden cord tied to button hole, ear plug case, or shoe laces
  •           Daily intake (1 knot/black bead per canteen)
  •           Urine monitoring techniques (know limitations)

          - Track High risk personnel: Use red beads or red armband/Velcro patch for "at-risk" Soldiers

          - Place water at key points e.g., at land nav objectives

          - Provide and monitor: Electrolyte drinks and meal intake

Change events and activities to minimize heat load

          - Avoid back-to-back strenuous days, especially during Heat Category 4-5

          - Modify time of day - complete activities earlier/later

          - Adjust activity

                    Reduce pace and/or distance

                    Allow for more frequent rest breaks

                    Encourage Soldiers to rest in the shade whenever possible

          - Reduce clothing and load:


                    Backpacks, body armor, helmets, etc. (training)

          - Dump excess heat

                    Allow/provide field shower

                    Cool overnight temperatures (fans, air conditioning, cool showers) 


Be familiar with signs/symptoms of EHI

          - Look for mild signs/symptoms à stop from progressing

          - Take immediate action when EHI is observed or suspected

          - When in doubt, call 911 and begin cooling!!


          - "What are heat illness signs/symptoms?"

          - "Do you have your HIP (Heat Injury Prevention) Pocket Guide card?"

          - "What is the current Heat Category?"

          - "Who is at risk?" "Who is their buddy?"

          - "What actions would you take if … "

          - Is water available and accessible?

          - Are rapid cooling supplies on-hand?

          - Do you have communication with medical support?

Spot check medical support

          - Check equipment, personnel, evacuation vehicle, communication, ice sheets.

          - If no organic medical support, check for coordination of alternatives (gate access for off-post EMS, travel time, procedures, etc.)

If a heat injury occurs, stop training and assess situation

          - Confirm Battle Buddy System is in place.

          - Monitor food intake (food/salty snack every 4 hrs or less).

          - Check Ogden cords for water intake. Are they drinking BEFORE PT in morning?

          - Monitor urine output (e.g. 'color test', and/or Soldiers should urinate a full bladder every 2-3 hours)

          - Ask questions that require clear thinking (What day is it? Where are you?).

          - Look for Soldiers who are visibly 'wilting' or struggling.

          - Look for Soldiers bypassing controls (e.g. not drinking in order to have a full canteen for an inspection).