NAVMED P-5010.pdf

Bureau of Medicine and Surgery NAVMED P-5010-3 (Rev. 0 8-2023) 7700 Arlington Blvd., Falls Church, VA 22042

Manual of Naval Preventive Medicine

Chapter 3

PREVENTION OF HEAT AND

COLD STRESS INJURIES

(ASHORE, AFLOAT, AND GROUND FORCES)

DISTRIBUTION STATEMENT "A"

This publication supersedes NAVMED P-5010-3 of 2009 S/N 0510-LP-108-2696.

NAVMED P-5010-3

Chapter 3 Manual of Naval Preventive Medicine

Heat and Cold Stress Injuries (Ashore, Afloat, and Ground Forces)

15 Aug 2023

To: Holders of the Manual of Naval Preventive Medicine

1. Purpose. This revision provides guidance intended to be used in the prevention and treatment of heat and cold stress injuries. The information in this chapter describes the physical and physiological measurements necessary to assess the effects of hot and cold environmental conditions for ashore, afloat, and ground forces.

2. Background. The Navy and Marine Corps Force Health Protection Command (NAVMCFORHLTHPRTCMD) Technical Manual, NEHC-TM-OEM 6260.6A, Prevention and Treatment of Heat and Cold Stress Injuries, contains more detailed information on this topic.

3. Information Management Control. Reports required in article 3-9c and article 3-22a and 3-22b of this manual are exempt from reports control per Secretary of the Navy Manual 5214.1 of December 2005, part IV, subparagraph 7k.

4. Action. Replace entire Chapter 3 with this version.

Releasability and distribution:

This publication is cleared for public release and is available electronically only via the Navy Medicine Web site, https://www.med.navy.mil/directives/Pages/Publications.aspx https://www.med.navy.mil/Portals/62/Documents/NMFA/NMCPHC/root/Occupational%20and%20Environmental%20Medicine/5Heat_and_Cold_final_June07.pdf?ver=ObEsAmCeliMRHOMn1YJFGA%3d%3d https://www.med.navy.mil/directives/Pages/Publications.aspx

CHAPTER 3

HEAT AND COLD STRESS INJURIES

ASHORE, AFLOAT, AND GROUND FORCES)

i

TABLE OF CONTENTS

Page

SECTION I. INTRODUCTION .............................................................................................. 3-1

3-1. Purpose ........................................................................................................... 3-1

3-2. Thermal Stress and Strain .............................................................................. 3-1

3-3. Roles and Responsibilities ............................................................................. 3-1

SECTION II. HEAT STRESS ................................................................................................. 3-3

3-4. Heat Stress Effects ......................................................................................... 3-3

3-5. Environmental Measurements ....................................................................... 3-3

3-6. Preventive Measures ...................................................................................... 3-8

3-7. Heat Illnesses and Injuries ........................................................................... 3-14

3-8. Treatment of Heat Stress Injuries ................................................................ 3-17

3-9. Training and Reporting ................................................................................ 3-19

3-10. Ship Design Resources.. .............................................................................. 3-19

3-11. Afloat. .......................................................................................................... 3-19

3-12. Shore and Ground Forces............................................................................. 3-31

SECTION III COLD STRESS .............................................................................................. 3-35

3-13. Cold Stress Effects ....................................................................................... 3-35

3-14. Temperature and Wind ................................................................................ 3-35

3-15. Environmental Measurements - Wind Chill ................................................ 3-35

3-16. Afloat Personal Protection ........................................................................... 3-36

3-17. Preventive Measures .................................................................................... 3-37

3-18. Cold Water Immersion ................................................................................. 3-40

3-19. Cold Stress Exposure Injuries ...................................................................... 3-42

3-20. Other Injuries Related to Cold Weather ....................................................... 3-45

3-21. Treatment of Cold Stress Exposure Injuries. ............................................... 3-46

3-22. Cold Stress Injuries Reporting Requirements .............................................. 3-47

ASHORE, AFLOAT, AND GROUND FORCES)

ii

LIST OF TABLES

Page

Table 3-1. Risk Factors and Conditions that Predispose to Heat Stress Injuries ..................... 3-9

Table 3-2. Regulating Physical Exertion in Hot Weather by Wet-Bulb Globe Temperature (WBGT) Index ................................................................................. 3-11

Table 3-3. Physiological Heat Exposure Limits (PHEL) Curve General Applicability Aboard Ships ......................................................................................................... 3-23

Table 3-4. PHEL Time Limits for PHEL Curves I-VI without the Presence of Fuel Combustion Gases or Fuel Vapors ....................................................................... 3-25

Table 3-5. PHEL Time Limits for PHEL Curves I-VI with the Presence of Fuel Combustion Gases or Fuel Vapors ....................................................................... 3-27

Table 3-6. Remaining Safe Stay Time Equation .................................................................... 3-28

Table 3-7. Measures to Limit Heat Stress and Reduce Incidence of Heat Casualties ........... 3-30

Table 3-8. Sample Calculation of Estimated WBGT ............................................................. 3-31

Table 3-9. American Conference of Governmental Industrial Hygienists (ACGIH) Threshold Limit Values (TLV)® and Work and Rest Criteria .............................. 3-32

Table 3-10. Examples of Work Levels for Navy and Marine Corps Activities ....................... 3-32

Table 3-11. Classification of Hypothermia .............................................................................. 3-44

LIST OF FIGURES

Figure 3-1. How We Gain or Lose Heat to the Environment .................................................... 3-2

Figure 3-2. QUESTemp 48N ..................................................................................................... 3-7

Figure 3-3. Automated Heat Stress System (AHSS) Unit ......................................................... 3-7

Figure 3-4. Exertional Collapse/Incapacitation Field Algorithm ............................................ 3-18

Figure 3-5. PHEL Chart ........................................................................................................... 3-20

Figure 3-6. Urine Chart............................................................................................................ 3-34

Figure 3-7. National Weather Service Wind Chill Temperature Index ................................... 3-36

Figure 3-8. Survival Time in Cold Water (Estimated) ............................................................ 3-41

Figure 3-9. Recommended Cold Water Immersion Postures .................................................. 3-42

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SECTION I. INTRODUCTION

3-1. Purpose

a. This chapter provides guidance to be used in the prevention and treatment of heat and cold stress injuries. The information contained in this chapter describes the physical and physiological measurements necessary to assess the effects of hot and cold environmental conditions for ashore, afloat, and ground forces. Target audience for this document is preventive medicine and providers caring for personnel potentially suffering from the effects of heat and cold exposure.

b. The Navy and Marine Corps Force Health Protection Command (NAVMCFORHLTH- PRTCMD) Technical Manual, NEHC-TM-OEM 6260.6A, Prevention and Treatment of Heat and Cold Stress Injuries, contains more detailed information on this topic.

3-2. Thermal Stress and Strain

a. Thermal stress is a combination of multiple factors affecting the body’s gain or loss of heat (environmental, physiological, and clothing). Figure 3-1 shows how the body gains or loses heat to the surrounding environment.

b. Environmental physiologists employ the term “stress” to designate the force or load acting upon the biological system and the term “strain” to designate the resulting distortion of the biological system. Thermal stress factors include heat, cold, humidity, radiation, air movement, and surface temperatures. Thermal strain manifests itself in specific cardiovascular, thermoregulatory, respiratory, renal, and endocrine responses.

3-3. Roles and Responsibilities

a. Afloat Forces: Follow guidance as set forth in the OPNAVINST 5100.19F.

b. Ashore Forces: Follow OPNAVINST 5100.23H and Occupational Safety and Health Administration regulations, where applicable. Per MARADMIN 111/15, Officers, staff noncommissioned officers, noncommissioned officers, and other supervisors should ensure Marines, Sailors, and civilian personnel are familiar with heat and cold stress injury prevention.

https://www.med.navy.mil/Portals/62/Documents/NMFA/NMCPHC/root/Occupational%20and%20Environmental%20Medicine/5Heat_and_Cold_final_June07.pdf?ver=ObEsAmCeliMRHOMn1YJFGA%3d%3d

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Figure 3-1. How We Gain or Lose Heat to the Environment

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SECTION II. HEAT STRESS

3-4. Heat Stress Effects

a. Heat stress and heat strain have immediate, and possible long-term effects on humans.

The immediate effects are reduced performance and efficiency, and, if there is heat injury, lost duty time due to systemic heat injury. Prolonged or severe exposure, is viewed as contributing to:

(1) Progressive loss of performance capability

(2) Increased susceptibility to other forms of stress

(3) Reduced heat tolerance

b. Each individual should know how to minimize heat stress, recognize symptoms of heat illness and injury, and provide basic first aid.

3-5. Environmental Measurements

a. Dry-Bulb (DB) Temperature. DB is the prevailing air temperature measured with an ordinary alcohol-in-glass thermometer whose bulb is kept dry and shielded from radiation (radiant heat, such as sunlight).

b. Wet-Bulb (WB) Temperature. WB is measured with a thermometer, similar to that used for DB temperature, except that a wet wick is fitted closely over the bulb (or sensor). A “natural” WB temperature is obtained with no movement of air over the wick except that which occurs naturally in the environment (unventilated areas will have little air movement, while ventilated or outdoor areas will have more). Although the natural WB temperature depends on the DB temperature and the moisture content of the air, it does not provide a direct indication of the amount of water vapor in the air. The WB temperature is of greater value in planning corrective engineering actions than the “natural” WB temperature. Use of psychometric WB has been the Navy standard for over 40 years. When the WB and DB temperatures are identical the air is said to be “saturated,” and the relative humidity (RH) is considered to be 100 percent. Any decrease in the moisture content of the air will result in evaporation from the wick of the WB thermometer, and the thermometer will be cooled to a temperature that reflects the reduced moisture content of the air.

c. Humidity. Humidity is an expression of the quantity of water vapor mixed with other atmospheric gases. The absolute humidity (AH) is the mass of water vapor present per unit volume of air (kg/m3); the gas pressure (Torr) exerted by this water vapor is referred to as the vapor pressure. The ratio of the actual amount of water in the air (AH) to the maximum quantity of water that the air can hold at a given temperature is the RH. The temperature at which the AH reaches a maximum and the air becomes saturated with water vapor is called the dew point (Td).

Vapor pressure is a measure of water content in the atmosphere under given conditions.

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d. Psychrometer. A psychrometer is an instrument for measuring atmospheric humidity utilizing a DB and WB thermometer and whirled manually or by motorized unit to provide the airflow necessary to obtain WB temperature reading. A psychrometric chart helps translate this information into RH values and other thermodynamic characteristics of moist air. Motorized psychrometers should be used for reproducibility of measurements. The national stock number (NSN) for the approved unit is IH-6685-00-935-1389; calibration is not required. Electronic, motorized psychrometers are available to provide direct readout of DB, WB, RH, and Td. Air movement or velocity is usually expressed in feet per minute (fpm) or cubic feet per minute (cfm). Depending upon the velocity of air movement, airflow is measured using different instruments. Low velocities (down to 10 fpm) require a heated kata thermometer (heated alcohol thermometer) or thermo-anemometer (“hot-wire” anemometer or equivalent); high unidirectional air velocities may be measured with a velometer or vane anemometer.

e. Radiant Heat. Radiant heat is the transfer of thermal energy from one object to another without warming of the intervening space. The wave lengths involved range from the visible portion of the electromagnetic spectrum (0.3-0.7 microns) to the longer radio waves. In industrial situations, any part of the heat radiation spectrum may be present. Natural environments generally include two bands: solar radiation from ultraviolet to near infrared, and heat radiation in the far infrared portion of the spectrum. Both forms of radiation liberate thermal energy when absorbed.

Not all of the radiant heat that strikes a surface is absorbed. Any surface that has a high reflectance will minimize absorption of radiant heat; conversely, a surface with low reflectance will increase absorption of radiant heat. Humans with dark-pigmented skin and light-colored skin are essentially alike in absorbing the longer wavelength radiant heat (e.g., indoors); however, in the sunlight darker skin has a higher absorbance than lighter skin. The intensity of radiant heat can be measured by use of a radiometer (e.g., pyrheliometer), or a globe thermometer (GT).

f. GT

(1) GT is measured using the Vernon GT technique, which consists of a 6-inch hollow copper sphere, with a 0.022 inch thick wall, painted matte (flat) black on the outside, and contains a temperature sensor like that of an unshielded DB thermometer with its bulb, or an equivalent, at the center of the sphere. The black globe temperature typically requires about 20 minutes to reach equilibrium (i.e., to accurately reflect environmental temperature). Smaller globes, from 1.64-2.0 inch outside diameter, have been developed which have shorter equilibrium time. However, the GT value obtained from the smaller globe should be equated to a GT value from a 6-inch globe using a mathematical algorithm to obtain an accurate Vernon GT measurement. GTs is required in the assessment of thermal stress because they integrate radiant heat exchange and convective heat loss into a single value.

(2) The GT value is neither radiant heat by itself nor what is known as the “mean radiant temperature.” The GT value is a composite of radiant and convective heat transfers.

(3) While there are several heat stress equations or indexes that provide heat exposure, the only index authorized by the Bureau of Medicine and Surgery (BUMED) is the Wet-Bulb Globe Temperature (WBGT) index.

https://humiditycontrol.com/psychrometric-chart/

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g. Heat Stress Index (HSI). The HSI provides heat exposure guidance only using DB and RH values and does not incorporate GT. The HSI is not the same as the heat index (HI). The HI was established by the National Weather Service for weather purposes and provides a number of how hot it may feel to a person.

h. Wet Globe Temperature (WGT) Index. The WGT or “Botsball” has been used in the distant past to obtain heat stress measurements. However, BUMED does not endorse use of the WGT Botsball to determine heat stress guidance for Navy and Marine Corps personnel.

i. WBGT Index

(1) WBGT is unique in that it takes into account the four physical variables of the thermal environment (air temperature, DB; humidity, RH or WB; radiant heat, GT; and air movement).

WBGT is obtained from the measurement of DB, GT, and WB (measured directly or derived from RH) and is calculated as (DB x 0.1) + (GT x 0.2) + (WB x 0.7). While there are numerous WBGT equations, the above equation is the standard for all Navy and Marine Corps environments (indoor and outdoor). Direct measurement of air velocity is not necessary and the GT integrates radiant heat and convective heating and cooling into one value.

(2) Other indices of heat stress and strain are of limited use. No other value is to be used to calculate stay times, determine flag conditions, etc.

(3) The requirement to measure WBGT generally is determined by DB temperature, duration of work exposure, and intensity of work (effort).

(4) Frequency of WBGT Index measurement

(a) Shipboard temperatures are monitored using DB thermometers, with frequency of temperature measurement determined by whether DB temperatures exceed 85°F: if DB temperatures do not exceed 85°F, then temperatures are measured every 4 hours; if DB temperatures do exceed 85°F, then temperatures are measured every hour. For less strenuous work (physiological heat exposure limits (PHEL) curves I through III), if watch or work length is 4 hours or less, then WBGT readings must be taken if the DB temperature is 100°F or more; if watch or work length is greater than 4 hours, then WBGT readings must be taken if the DB temperature is 90°F or more. For more strenuous work (PHEL curves IV through VI), WBGT readings must be taken if the DB temperature is 85°F or more. (Heat stroke fatalities have occurred at temperatures below 85°F, so the requirement to take WBGT readings above 85°F does not imply heat stress is not a concern below that temperature, especially if strenuous exertion, extra clothing, or other factors are involved.) OPNAVINST 5100.19F, section B, chapter 2, subparagraph 3b(3)(a) through 3b(3)(c) contains instructions on frequency of shipboard WBGT measurements.

(b) Shore guidance for the WBGT Index is not detailed in any DoD or Defense Health Agency (DHA) level instruction (Technical Manual NEHC-TM-OEM 6260.6A provides WBGT Index information). Many activities now use the Automated Heat Stress System (AHSS) https://www.med.navy.mil/Portals/62/Documents/NMFA/NMCPHC/root/Occupational%20and%20Environmental%20Medicine/5Heat_and_Cold_final_June07.pdf?ver=ObEsAmCeliMRHOMn1YJFGA%3d%3d

15 Aug 2023 3-6 which records WBGT readings continuously, see article 3-5j(3). If a command has no AHSS, it is reasonable for shore commands to measure WBGT every 4 hours if DB (air) temperatures do not exceed 85°F, and every hour if DB temperatures exceed 85°F (i.e., following a schedule similar to shipboard units) and during training evolutions.

j. Equipment

(1) WBGT Meter, also known as a heat stress meter, is the approved DHA environmental measurement device. The heat stress meter is a compact instrument that independently measures the DB temperature, WB temperature or RH, and globe temperature. The instrument displays each of these values as well as computes and displays the WBGT Index value. Currently, the approved heat stress meters are identified in article 3-5j(1)(a) through 3-5j(c):

(a) The QUESTemp 48N (figure 3-2).

(b) The AHSS, figure 3-3, is described in article 3-5j(3) is a legacy heat stress meter, no longer available in the stock system. This meter may be used until it is no longer repairable.

(c) The Stortz WBGT Kit; is primarily used by Marine Corps personnel in the field.

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A B C

A. Globe thermometer B. Relative humidity sensor C. Dry bulb thermometer

Figure 3-2. QUESTemp 48N Figure 3-3. AHSS Unit

(2) The two heat stress meters authorized for shipboard use are the legacy RSS-220 and the QUESTemp 48N. The replacement meter for the legacy RSS-220 is the QUESTemp 48N.

Functional RSS-220 meters can continue in service; however, when no longer repairable must be replaced with QUESTemp 48N meters. Like the RSS-220, the QUESTemp 48N has a 3-year laboratory calibration requirement. Follow manufacturer calibration requirements (most models require annual calibration). The Planned Maintenance System for the Quest 48N is available under the Maintenance Index Page 4361. Instead of a rechargeable battery pack, the QUESTemp 48N heat stress meter uses a 9-volt battery with an optional AC adaptor. The QUESTemp 48N performs traditional heat stress monitoring without maintaining a wet bulb. Mathematical models were developed to create a waterless wet bulb calculation through a combination of dry bulb temperature, globe temperature, RH, and air flow. Empirical data indicates that these calculations are accurate. The QUESTemp 48N displays the WBGT value and automatically calculates and displays stay times in order to manage work and rest regimens as defined in the American Conference of Governmental Industrial Hygienists (ACGIH) Threshold Limit Values (TLV) Handbook, U.S. Navy PHEL charts, and Flag Conditions for U.S. Navy/Marine Corps Ashore.

(3) The AHSS provides a measurement of WBGT through the use of a DB, GT, and RH sensor. This computerized system automatically measures the WBGT environment and calculates the appropriate heat exposure guidance for both afloat and ashore personnel. The AHSS displays the data every minute, stores the data in a file on the computer hourly, and can print out a heat stress survey on demand. A WB value (psychometric/WB value) is derived from

15 Aug 2023 3-8 the measured DB and RH values. The advantage of using an RH sensor is that the RH value can provide information on the potential for evaporation of sweat to cool the body (i.e., 15 percent RH is a dry environment while 75 percent RH is a humid or wet environment). In contrast a WB value is of little use without knowing the DB value. Additionally, the RH sensor does not require constant maintenance to keep the wick clean and properly wetted. Use of the AHSS has been implemented afloat to provide PHELs stay time guidance and ashore to provide flag condition guidance. AHSS units do not need calibration stickers.

(4) Commands may use commercial off-the-shelf (COTS) portable direct reading WBGT heat stress monitors for shore establishment measurements. Ensure GT is Vernon 6-inch equivalent and the overall measurement accuracy is within 1°F or 0.5°C. With any heat stress meter, careful monitoring and adherence of procedures and equipment maintenance is necessary to ensure valid assessment of WBGT conditions. For all measurements, ensure that:

(a) Outside readings are measured in an area that is not shaded and is likely to reflect conditions experienced by troops.

(b) Heat stress meters are kept clean, calibrated, and operational. WB measurements are taken using a clean 100 percent cotton wick which extends into clean, non-mineralized water, and above the thermometer reservoir; or a RH sensor provides the WB reading for the WBGT calculation instead of a WB thermometer, as in the QUESTemp 48N.

(c) Heat stress data is consistently recorded in a heat stress log.

(5) Stock numbers for the Navy and Marine Corps approved WBGT meters and accessories as listed:

• The QUESTemp 48N, NSN 6685-01-584-0785 (Shipboard AEL 2-870003051).

• Standard Nickel-Cadmium Rechargeable AA Batteries, NSN 90-6140-449-6001.

• AHSS Unit, NSN 7H H 6685-LL-H54-6414.

• The Stortz WBGT Kit, NSN 6665-00-159-2218.

• RSS-220 WBGT Meter, NSN 7G-6685-01-055-5298 (Shipboard AEL 2-

870003051).

• Accessories (spare sensor/wind tunnel assembly, globe, wicks, etc.)

NSN 90-6685-01-055-5299 (Shipboard APL 100l10001).

• Globe Assemblies NSN 90-6665-01-149-8635.

3-6. Preventive Measures

a. Controlling Risk Factors

(1) Heat disorders have a worldwide distribution and may even occur in cold climates where metabolic heat production exceeds an individual's adaptive abilities. Heat stress is commonly encountered in military operations, and may cause injury or death, resulting in decreased readiness.

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(2) Most heat stress injuries are preventable. The body constantly generates heat; activity (work or exercise) generates more heat. The body cools itself in heat stress conditions primarily by sweating. Risk factors and conditions that predispose to heat stress injuries are listed in table 3-1:

Table 3-1. Risk Factors and Conditions that Predispose to Heat Stress Injuries

1. High humidity

2. Lack of air movement (wind)

3. Overhead sun

4. Elevation below sea level

5. Sunburn or other skin condition

6. Clothing or gear that hinders skin “breathing”

7. Illness

8. Recent immunizations

9. Prior heat injury

10. Recent heat stress exposure

11. Age (very young or very old)

12. Lack of acclimatization (a new exposure to a hot, humid environment)

13. Dehydration

14. Medications

15. Substance abuse

16. Fatigue

17. High activity level

18. Being around very hot objects (e.g., hot steel)

(3) Preventive measures against heat stress injury are focused on limiting exposure to heat stress (by decreasing activity or avoiding hot environments), acclimatization (taking 3 weeks to gradually get used to the heat), maintaining adequate hydration and limiting strenuous activity. Activity is controlled by observing work-rest cycles, which are established based on the WBGT index.

b. Warning Signs of Heat Strain

(1) Symptoms (feelings of being overheated or of chills) and signs (confusion, incoordination, decreased sweating, and “gooseflesh”) of impending heat stroke should be closely followed. Although body temperature measurement should ideally be measured with a rectal thermometer, oral (mouth) thermometers (provided the person has not had hot food or water for 5 minutes and cold food or water for 30 minutes) or ear probes (provided no water has splashed in the ear) may be used instead if a rectal thermometer is unavailable.

(2) Supervisory personnel should be able to recognize the signs and symptoms of excessive heat strain and impending heat stroke and heat exhaustion. Chapter 11 of NEHC-TM- OEM 6260.6A provides information on the signs and symptoms of heat stress injuries. Also, the medical department representative can provide training to supervisory personnel on the signs and symptoms of heat stress injuries.

https://www.med.navy.mil/Portals/62/Documents/NMFA/NMCPHC/root/Occupational%20and%20Environmental%20Medicine/5Heat_and_Cold_final_June07.pdf?ver=ObEsAmCeliMRHOMn1YJFGA%3d%3d https://www.med.navy.mil/Portals/62/Documents/NMFA/NMCPHC/root/Occupational%20and%20Environmental%20Medicine/5Heat_and_Cold_final_June07.pdf?ver=ObEsAmCeliMRHOMn1YJFGA%3d%3d

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c. Engineering Controls. Increased ventilation, insulating warm or heat generating equipment or items from workers, isolating heat generating equipment or items (e.g., steam generating plant equipment) and processes from workers and work spaces, implementing structural cooling controls, or locating heat generating processes near outdoor air or cool water, etc., can minimize worker exposure to heat stress.

d. Administrative Controls. Engineering methods are not always effective and often must be supplemented or preceded by other measures. In physiologically compensable environments, performance in the heat can be improved greatly by proper selection and acclimatization of workers. In all hot environments, improved performance can be achieved by controlling fatigue, nutrition and alcohol, and by periodic examination for underlying illness and the early symptoms of heat strain.

(1) Scheduling Activity. Training exercises requiring sustained or severe physical effort, and those conducted in the prone position should be scheduled, when possible, in early morning or at night as radiant heat from the sun and hot ground will add additional stressors to persons exposed. Outdoor classes should be conducted in the shade with adequate exposure to cooling wind. When environmental heat stress is excessive, heat illness can be prevented by curtailing or suspending non-essential physical training (PT) and undue heat stress exposure. If operational mission requirements, excluding training programs, may preclude application of pertinent heat stress guides, the Medical Department should be forewarned in order to adequately prepare facilities and staff for an anticipated increase in number of heat illnesses. Mental and physical dysfunction under thermal stress may be expected to amplify the frequency of accidental injury and mishaps.

(2) Flag Conditions

(a) Flag condition refers to a series of outdoor WBGT environments that provide ashore heat exposure or physical activity guidance to Navy and Marine Corps personnel.

(b) Flag condition guidance, contained in table 3-2, is not a substitute for the PHEL curves nor is it possible to comply with this guidance in combat situations. When the WBGT Index reaches specific temperatures, color-coded flags are flown in strategic locations so all personnel will be aware of the current heat stress index and make appropriate work schedule adjustments. Since shore facilities vary in size geographically, the flag closest to the specific site during hot weather operations should be used to determine level of the specific operation.

1. White Flag (WBGT Index below 80°F). Extremely intense physical exertion may precipitate heat exhaustion or heat stroke.

2. Green Flag (WBGT Index of 80°F to 84.9°F). Heavy exercises for non-acclimatized personnel will be conducted with caution and under constant supervision.

Organized PT evolutions in boots and utilities are allowed for all personnel.

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3. Yellow Flag (WBGT Index of 85°F to 87.9°F). Strenuous exercises, such as marching at standard cadence, will be suspended for non-acclimatized troops in their first 3 weeks of heat exposure. Avoid outdoor classes in direct sunlight.

4. Red Flag (WBGT Index of 88°F to 89.9°F). All PT will be halted for those troops who have not become thoroughly acclimatized by at least 12 weeks of living and working in the area. Those troops who are thoroughly acclimatized may carry on limited activity not to exceed 6 hours per day.

5. Black Flag (WBGT Index of 90°F and above). All strenuous outdoor physical activity that is not essential (including organized, unit, or individual PT) mission requirements will be halted for all units.

(c) Wearing body armor or nuclear, biological, or chemical (NBC) protective uniforms adds approximately 10 points to the measured WBGT. Limits of exposure should be adjusted accordingly.

(d) PHEL curve and Flag condition heat exposure guidance are based solely on WBGT index. Use of the heat stress index (or any measurement other than WBGT) to provide PHEL or Flag guidance is not authorized.

Table 3-2. Regulating Physical Exertion in Hot Weather by Wet-Globe Temperature (WBGT) Index

Flag Color WBGT Index(°F) Intensity of Physical Exercise

White

Less than 80 Extremely intense physical exertion may precipitate heat exhaustion or heat stroke.

Green

80 – 84.9 Discretion required in planning heavy exercise for unseasoned personnel.

Yellow 85 – 87.9

Strenuous exercise and activity (e.g., close order drill) should be curtailed for new and non-acclimatized personnel during the first 3 weeks of heat exposure.

Red 88 – 89.9 Strenuous exercise curtailed for all personnel with less than 12 weeks training in hot weather.

Black 90 and Above

PT training and strenuous exercise suspended for all personnel (excludes operational commitment not for training purposes).

Note: This table may not be used in lieu of the PHELs for afloat commands.

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(3) Essential Outdoor Physical Activity will be conducted at a level appropriate for the degree of personnel heat acclimatization as determined by the unit’s commanding officer in coordination with the unit’s medical officer or medical personnel. All efforts should be made to reschedule major hot weather training activities to occur during cooler periods of the day, such as early morning or late evening.

(4) Recovery. Adequate recovery from acute or cumulative fatigue (at least 7 hours of uninterrupted sleep in a thermally comfortable environment per 24 hours), optimal physical fitness for the work to be done, and absence of illness and febrile reactions (e.g., elevated body temperature following immunization) will increase resistance to heat stress injury.

(5) Clothing. Clothing should be worn loosely at the neck, at the cuffs of sleeves, and at the bottom of trousers to facilitate convective cooling (cool air carrying heat away from the body). Wearing Navy coveralls over any other clothing imposes a major heat load upon the body due to added insulation and weight, and is not recommended in hot, humid environments.

Starch must not be utilized where evaporative cooling from clothing is a major factor. Outdoors, helmet liners or headgear of similar design provide more cooling and protection of the head than caps.

e. Sweating. Evaporation of perspiration from the skin (sweating) is the primary way the body loses heat when the air temperature exceeds 95°F. Evaporative heat loss from the respiratory mucosal surfaces is minimal, representing perhaps only 2 percent of the metabolic heat. Thermoregulation is mediated by circulatory (e.g., central and capillary blood flow), neural (e.g., hypothalamic, autonomic pathways), and biochemical (e.g., ionic and endocrine) functions involving central or peripheral levels of response.

(1) When temperature balance mechanisms for the body fail, the body’s core temperature will continue to increase. As heat storage increases, skin and deep-tissue temperature rise, cardiovascular, respiratory and metabolic functions accelerate, and renal function is depressed.

(2) Increased metabolic heat pushes the cycle faster to the point of cardiovascular and renal failure and irreversible damage to the nervous system and muscles. The cycle can be broken only by timely and definitive therapy. Therefore, every effort should be made to relieve excessive heat stress.

f. Acclimatization. Acclimatization is important to prevent heat stress injuries, and is defined as the process of physiologic adaptation to heat stress conditions. (Although previously used here interchangeably with acclimatization, acclimation most accurately refers to short-term adaption to heat stress under laboratory conditions. Acclimatization is the proper term applicable to naval personnel.) Acclimatization is accomplished by incrementally increasing daily exposure to exertion in heat stress and takes approximately 3 weeks to complete. Advantages of acclimatization are listed in article 3-6, subparagraphs 3-6f(1) through 3-6f(8):

(1) Tolerance of and performance in heat stress conditions is improved.

(2) Sweat rate increases and begins at a lower core temperature.

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(3) Sweat sodium concentration decreases.

(4) Plasma volume increases.

(5) During exercise in the heat there is lowered heart rate and lowered core temperature at each level of sub-maximal workload.

(6) A decrease in perceived exertion.

(7) The level of hyperkalemia is attenuated after acclimatization (mild exercise in severe heat conditions induces significant hyperkalemia).

(8) Individuals exercising in the heat have an increased ability to conserve sodium. Heat acclimatization occurs more rapidly in persons who are physically fit. Physical conditioning is also advantageous in the body’s response to dehydration, a heat stress-related condition.

Inactivity results in decreased acclimatization after only a few days or weeks, and exposing heat-acclimatized individuals regularly to cold temperatures (e.g., 4 hours daily for 21 days) can cause a significant loss in heat acclimatization. To achieve maximum benefits from acclimatization, it is extremely important that moderate (i.e., more than sedentary) work be performed during the adaptation process and moderate work be maintained regularly to remain acclimatized. Stable acclimatization at any one level of heat stress does not guarantee full acclimatization to a higher level of heat stress. Various body systems adapt at different rates.

g. Fluids (Drinks). Water and electrolyte solutions (e.g., sports drinks) may be used to replace fluids lost through sweating. Water is generally adequate, readily available, and should be encouraged as the main means of hydration. The extra electrolytes in sports drinks are not necessary, and soft drinks contain high amounts of sugar, carbonation and acidity. Supervisory personnel must know that personnel cannot be trained to resist dehydration. “Water discipline” or “water hardening” (i.e., learning to go without water in the heat) is a false concept that must be replaced with “water freedom” where drinking moderate amounts of cooled water at frequent intervals is encouraged. “Forced drinking” (i.e., drinking even though not thirsty) during activity in hot environments should be used, as thirst lags behind actual need for water by up to 4 hours.

An individual may lose up to 2 percent of body weight before feeling the sensation of thirst.

h. Salt (Sodium Chloride). Salt intake is especially important in the early stages of heat acclimatization. The current estimated “'normal”' dietary intake of salt in the general United States population is about 3,400 mg daily, and is generally adequate even in the early stages of heat acclimatization (when salt concentration in sweat is highest, thus salt loss is also highest).

Use of salt tablets during exercise in the early stages of acclimatization, if required, must be closely monitored by medical personnel. Proper sodium chloride levels can be achieved by providing adequate water, a normal diet, and a salt shaker on the table. Deviations from these recommendations must be governed by the past and present medical histories of individual workers and adjusted according to individual need by the medical department representative.

Field rations contain a variable amount of sodium chloride, depending upon the Federal Stock Number and the manufacture dates. Standard military rations, including A ration, B ration, 15 Aug 2023 3-14

T ration, meal, ready-to-eat, and the go to war ration, contain 5-7 grams of sodium (about 12.5-

17.5 grams of salt) per meal. Restricted rations, including ration, lightweight (RLW-30), food packet, long range patrol, and food packet, survival, general purpose improved, contain 2.5-3.5 grams of sodium (about 6.5-9 grams of salt) per meal. Field grade salt tablets are 10 grain (0.648 grams; 0.255 grams of sodium and 0.393 grams of chloride) each.

i. Cooling Systems. Some microclimate cooling systems have been shown to be a safe and effective means of reducing or preventing the ill effects of heat stress. There may be highly specialized applications of such units, but each is to be carefully examined with sufficient supporting data. Where possible, the key issue is to perform the necessary corrective engineering actions to eliminate impedances of the workers and permit the workers to perform their normal duties in an effective manner without physical encumbrances. However, there are environments, work locations, or work activities where engineering actions are not feasible or are inadequate and a cooling system may be appropriate. Cooling systems should be evaluated before implementation as vendors have become very aggressive in marketing their product directly to commands without the appropriate medical and scientific evaluation. Each cooling system is to be evaluated with regard to the effectiveness to provide adequate cooling with little impact on ergonomics, unrestricted body movement, and optimum safety of personnel. As such, all cooling garment products should be evaluated by the DHA and the appropriate Navy Medicine readiness and training command or Navy Medicine readiness and training unit prior to procurement and use.

Some microclimate cooling systems may require a more comprehensive physiological and environmental evaluation by the appropriate Navy testing and evaluation authority.

j. Other Cooling Methods. Immersion of hands and forearms in cool water (approximately 50°F, for example) for 10 minutes during rest breaks may expedite recovery from heat stress when exercising with NBC protective garments.

3-7. Heat Illnesses and Injuries

a. Military populations are prone to heat disorders because battle or training may increase heat stress and limit normal compensatory behavior (such as seeking shade, resting, and drinking water).

b. Acclimatization measures for newly arriving personnel should be followed to allow for an appropriate adjustment period due to exposure of new environmental conditions, preventing potential heat related illness and injuries.

c. The spectrum of heat illnesses ranges from mild to severe as body temperature increases:

(1) Hyperthermia. Hyperthermia (i.e., elevated body core temperature) results when the body’s cooling system is unable to regulate its temperature. This stress to the body can degrade mission performance and morale, increase the risk of accidents, and possibly risk the safety of fellow sailors, marines, and civilian personnel. Sweating is the primary mechanism to cool the body in heat stress conditions. If the signs of heat stress go unrecognized and untreated, serious, even life-threatening health problems can result, such as heat stroke.

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(2) Heat Rash (Miliaria). Heat rash is a skin irritation caused by heat stress exposure. It usually appears as tiny red bumps on the neck, groin area, or under the arms. Removing the person from heat or applying cooling water or water-based lotion can help relieve heat rash.

(3) Heat Syncope. Heat syncope (fainting) is most likely to occur when non-acclimatized personnel are first exposed to heat stress. It can usually be avoided by not requiring personnel to stand still in the heat (for example, standing in formation), particularly after exercise. Victims should be promptly removed to a cool place and allowed to rest.

(4) Heat Cramps. Heat cramps are painful cramps, usually affecting the extremities and abdomen. They primarily occur in individuals performing vigorous physical exercise in heat stress conditions. Heat cramps will decrease by reducing the intensity of exercise or ceasing physical activity. Electrolyte (e.g., salts such as sodium and potassium) replacement can lessen the intensity of heat cramps (use of salt tablets is not recommended). Remove the individual from direct sunlight or source of heat being generated, remove wet clothing, and have the individual drink water or a sports drink to help replenish the loss of nutrients.

(5) Heat Exhaustion. Heat exhaustion may be related to either dehydration or salt depletion. Call for medical assistance, and relocate the individual to a shaded, well ventilated area, and loosen or remove their clothing (unless in a chemical environment). Fan the individual and have them slowly drink at least one quart or one full canteen of water. Personnel must obtain medical treatment and clearance to ensure they are properly recovering and rehydrating prior to engaging in any activity.

(6) Heat Stroke. Heat stroke is the most serious form of heat injury and is considered a medical emergency (also known as “sun stroke”). When the body generates more heat than its capable of release via cooling methods, evaporative cooling via sweating fails, core body temperature rises rapidly as thermoregulation fails which results in the body losing its ability to self-regulate and cool down. Listed are noteworthy considerations and highlights of technical guidance:

(a) Heatstroke requires immediate medical treatment. Summon emergency medical services or transport the individual to the nearest military or civilian emergency room depending on circumstances.

(b) While seeking or waiting for emergency medical services, simultaneous efforts should:

1. Assess airway, breathing, circulation (blood pulse or pressure), and mental status.

2. Take immediate action to lower the affected individual’s body temperature via the best means available: remove from heat to a cool area or into shaded outdoor area, immerse in cold water tub, use a cooler filled with ice water to soak and place cold towels over body (rotate depending on quantity), use a shower or hose with cold water, use of an evaporative

15 Aug 2023 3-16 cooling blanket, assist in evaporative cooling using circulating air via fans, other mechanical devices, or other readily available methods. Refer to chapter 4 of NAVMCFORHLTHPRTCMD Technical Manual, NEHC-TM-OEM 6260.6A, Treatment of Heat Stroke.

(c) Common symptoms and signs include the following: high body temperature, heavy sweating with subsequent absence of sweating, rapid breathing and heart rate, confusion, agitation, nausea and vomiting, flushed skin, disorientation, headache, fatigue, bizarre behavior, combativeness, hallucinations, loss of consciousness, and coma.

(d) Diagnosis will be performed by observing the symptoms and signs of the patient during treatment by the appropriate medical authority.

(7) Rhabdomyolysis. Rhabodymyolysis (Rhabdo) is a medical condition, sometimes caused by heat stress and prolonged physical exertion, in which muscle fibers rapidly break down, die, and release electrolytes and proteins into the bloodstream. Left untreated this can lead to kidney damage, seizures, irregular heart rhythms, and death.

(a) Symptoms include muscle cramps, muscle pain, joint pain and stiffness, dark urine, weakness, and inability or decreased ability to perform physical exercise at the normally expected level or duration.

(b) Rhabdomyolysis is diagnosed in a clinical setting using laboratory tests that measure the level of enzymes, creatine kinease (CK) and creatine phosphokinease (CPK), that are elevated with muscle damage.

d. PT and other strenuous physical exercise often cause heat injuries, especially when an individual is:

(1) Inadequately hydrated.

(2) Inadequately acclimatized to the surrounding environment.

(3) Exposed to extreme heat, such as direct sunlight or heat producing equipment.

(4) Wearing personal protective equipment such as Joint Service lightweight integrated suit technology, firefighting ensemble, radiation protective suits, or other personal protective equipment.

(5) Inside closed spaces, such as inside an armored vehicle.

(6) Wearing body armor.

(7) Inadequately rested.

https://www.med.navy.mil/Portals/62/Documents/NMFA/NMCPHC/root/Occupational%20and%20Environmental%20Medicine/5Heat_and_Cold_final_June07.pdf?ver=ObEsAmCeliMRHOMn1YJFGA%3d%3d

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(8) Not completely recovered from heat exposure in the previous 24 hours.

(9) Taking certain medications (e.g., antihistamines, stimulants) or dietary supplements.

3-8. Treatment of Heat Stress Injuries

a. The treatment of heat stress injuries is beyond the scope of this document. The technical manual, Prevention and Treatment of Heat and Cold Stress Injuries at: NEHC-TM-OEM 6260.6A contains detailed guidance for treating heat stress injuries.

b. Medical texts, established military treatment facility procedures, the above technical manual, and experienced medical providers should be consulted as necessary.

c. All personnel should be aware that the essential first aid for victims of heat stress is immediate removal from heat stress and immediate, rapid cooling. Unless water intoxication is suspected, alert victims should be provided with cool or iced water to drink. Figure 3-5 depicts an algorithm for the response to heat stress collapse and incapacitation.

https://www.med.navy.mil/Portals/62/Documents/NMFA/NMCPHC/root/Occupational%20and%20Environmental%20Medicine/5Heat_and_Cold_final_June07.pdf?ver=ObEsAmCeliMRHOMn1YJFGA%3d%3d https://www.med.navy.mil/Portals/62/Documents/NMFA/NMCPHC/root/Occupational%20and%20Environmental%20Medicine/5Heat_and_Cold_final_June07.pdf?ver=ObEsAmCeliMRHOMn1YJFGA%3d%3d

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Figure 3-4 Exertional Collapse/Incapacitation Field Algorithm.

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3-9. Training and Reporting

a. Per MARADMIN 111-15 commanders and officers in charge (OIC) will ensure all potentially exposed ground forces personnel are initially trained in the causes, prevention, and treatment of heat injuries. After initial training, subsequent refresher training will be conducted at the discretion of the commander or OIC or whenever personnel are expected to be exposed to hot environments. Supervisors and those caring for personnel exposed to heat or cold stress should become familiar with the NAVMCFORHLTHPRTCMD Technical Manual, NEHC-TM- OEM 6260.6A, Prevention and Treatment of Heat and Cold Stress Injuries, summary chapters (chapters 11 and 12 in the 2007 edition).

b. Per OPNAVINST 5100.19F, section B, chapter 2, shipboard personnel will be trained in the causes, prevention, and treatment of heat injuries and the heat stress program.

c. Heat injuries will be reported through the Disease Reporting System internet (DRSi), found at Log In | DRSi (health.mil) or https://drsi.health.mil/NDRSi, per BUMEDINST 6220.12C and NAVMCFORHLTHPRTCMD Technical Manual, NMCPHC-TM 6220.12 (Medical Surveillance and Reporting). A simultaneous report will also be submitted to the Naval Safety Command per OPNAV M-5102.1 and MCO 5100.29C Vol 9. Reporting is submitted through the Risk Management Information - Streamlined Incident Reporting (RMI SIR) system. RMI can be located at https://afsas.safety.af.mil.

3-10. Ship Design Resources. Detailed engineering specifications that relate to heating and cooling design for ships are the responsibility of Naval Sea Systems Command and are found in the Naval Sea Systems Command Technical Manual, Heating, Ventilation, and Air-Conditioning…