d. When using the WBGT index in control of a physical activity, the proponents
of the WBGT index have proposed the following as a standard for application of the
index. IT SHOULD BE EMPHASIZED that the measurements must be taken in a
location, which is the same as, or closely approximates, the environment to which
personnel are exposed.
(1) When the WBGT index reaches 78F or 26 C (Heat Category 1), (see
Table 1-1) extremely intense physical exertion may precipitate heat exhaustion or heat
stroke; therefore, caution should be taken.
(2) When the WBGT index reaches 82 F or 28 C (Heat Category 2),
discretion should be used in planning heavy exercise for unseasoned personnel.
(3) When the WBGT index reaches 85 F or 29 C (Heat Category 3),
strenuous exercise such as marching at standard cadence should be suspended in
unseasoned personnel during their first three weeks of training. At this temperature,
training activities may be continued on a reduced scale after the second week of
At least 1
At least 1 1/2
90 and up
More than 2
* MOPP gear or body armor adds 10F to the WBGT index.
** An acclimatized soldier is one who had worked that condition
(temperature) for 14 days.
CAUTION: Due to high salt concentration in field rations, caution must be
taken to maintain a high water intake.
NOTE: "Rest" means minimal physical activity. Rest should be accomplished in the
shade if possible. Any activity requiring only minimal physical activity can be performed
during "rest" periods. EXAMPLES: Training by lecture or demonstration, minor
maintenance procedures on vehicles or weapons, personal hygiene activities, such as
shin and foot care.
Table 1-1. Heat injury prevention.