Annex B - Work/Rest Cycles & Recommended Water Intake
| WBGT (ºC) | Heat Risk Category |
Status of personnel |
Light Activity |
Moderate Activity |
Heavy Activity |
Very Heavy Activity + |
||||
|---|---|---|---|---|---|---|---|---|---|---|
Work/Rest |
Water intake L/hr |
Work/Rest |
Water intake L/hr |
Work/Rest |
Water intake L/hr |
Work/Rest |
Water intake L/hr |
|||
20.0-25.4 |
Very low |
Unacclimatised Acclimatised |
Continuous |
½ |
continuous continuous |
¾ |
40/20 min |
¾ |
30/30 min |
1 |
25.5-26.4 |
Very low |
Unacclimatised Acclimatised |
50/10 min continuous |
½ |
40/20 min continuous |
¾ |
30/30 min |
¾ |
20/40 min |
1 |
26.5-29.4 |
|
Unacclimatised Acclimatised |
40/20 min continuous |
½ |
30/30 min |
¾ |
20/40 min |
1 |
10/50 min |
1 |
29.5-30.9 |
|
Unacclimatised Acclimatised |
30/30 min continuous |
¾ |
20/40 min |
¾ |
10/50 min |
1 |
Avoid |
1 |
31.0-31.9 |
|
Unacclimatised Acclimatised |
20/40 min continuous |
¾ |
10/50 min |
¾ |
Avoid |
1 |
Avoid |
1 |
32+ |
|
Unacclimatised Acclimatised |
10/50 min |
1 |
Avoid |
1 |
Avoid |
1 |
Avoid |
1 |
Adapted from:
- USGS Survey Manual, Management of Occupational Heat Stress, Chapter 45, Appendix A
- Manual of Naval Preventive Medicine, Chapter 3: Prevention of Heat and Cold Stress Injuries
- OSHA Technical Manual Section III: Chapter 4 Heat Stress
- National Weather Service Tulsa Forecast Office, Wet Bulb Globe Temperature
- JSP 539 V 3.0 May 17 British Ministry of Defense; Heat Illness and Cold Injury: prevention and management. Part 2: Guidance.
Please Note:
Values in this table are applicable to personnel wearing a single layer uniform with sleeves rolled up and without a helmet. It applies to both men and women given comparable levels of fitness.
When wearing either CBRN protective clothing or body armour:
- Use the un-acclimatised WBGT index for all personnel
- Add 5oC to the WBGT value at the time
- If wearing either of these equipment, it is not safe to perform any activity listed under the category of "heavy activity" or "very heavy activity" or to run.
CAUTION:
- In Canada and for personnel working in similar northern climates, all personnel should be considered un-acclimatized.
- If a person did not pass his/her mandatory fitness test (Force Test), the work/rest cycle and recommended water intake to be followed for this individual is one heat risk category higher than the actual heat risk category. This will result in an increased rest period duration and decreased work period duration.
- If it is operationally necessary to undertake any activity outside of these guidelines, consideration should be given to reducing the duration of the work or task to less than an hour and to increase the duration and frequency of rest periods. Medical advice should be sought as needed.
- Drinking more than 15 liters of water per day greatly increases the risk of hyponatraemia. Symptoms may include vomiting and confusion. Hyponatremia can be fatal if not identified and treated immediately. Please consult with your senior medical authority if needed.