Annex B - Work/Rest Cycles & Recommended Water Intake

Table 2: Work/Rest Cycles & Recommended Water Intake
WBGT (ºC)

Heat Risk Category

Status of personnel

Light Activity
(office work, walking, close order drill with rifle, machining)

Moderate Activity
(walking quickly, jogging)

Heavy Activity
(BFT, aircraft refueling, fast jogging, obstacle course with light pack and rifle)

Very Heavy Activity +
(Heavy aircraft repair, speed marching 10km/hr, 15kg load)

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
Continuous

½
½

continuous continuous

¾
¾

40/20 min
50/10 min

¾
¾

30/30 min
40/20 min

1
1

25.5-26.4

Very low

Unacclimatised Acclimatised

50/10 min continuous

½
½

40/20 min continuous

¾
¾

30/30 min
50/10 min

¾
¾

20/40 min
40/20 min

1
1

26.5-29.4


Low

Unacclimatised Acclimatised

40/20 min continuous

½
½

30/30 min
50/10 min

¾
¾

20/40 min
40/20 min

1
1

10/50 min
30/30 min

1
1

29.5-30.9


Moderate

Unacclimatised Acclimatised

30/30 min continuous

¾
¾

20/40 min
40/20 min

¾
¾

10/50 min
30/30 min

1
1

Avoid
20/40 min

1
1

31.0-31.9


High

Unacclimatised Acclimatised

20/40 min continuous

¾
¾

10/50 min
30/30 min

¾
¾

Avoid
20/40 min

1
1

Avoid
10/50 min

1
1

32+


Extreme

Unacclimatised Acclimatised

10/50 min
50/10 min

1
1

Avoid
20/40 min

1
1

Avoid
10/50 min

1
1

Avoid
Avoid

1
1

Adapted from:

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:

  1. Use the un-acclimatised WBGT index for all personnel
  2. Add 5oC to the WBGT value at the time
  3. 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:

  1. In Canada and for personnel working in similar northern climates, all personnel should be considered un-acclimatized.
  2. 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.
  3. 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.
  4. 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.

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