Wet Bulb Globe Temperature (WBGT) combines humidity, radiant heat, air temperature, and — outdoors — direct sun load into a single index used to set occupational heat work/rest limits.
Outdoor (with solar load):
WBGT = 0.7·Tnwb + 0.2·Tg + 0.1·TdbIndoor (no solar load):
WBGT = 0.7·Tnwb + 0.3·TgTnwb is the natural wet bulb temperature (a wetted wick freely exposed to ambient air movement and radiation) — it is not the psychrometric wet bulb temperature from a sling or aspirated psychrometer, and the two must not be substituted for each other without a correction: natural wet bulb runs warmer under solar/radiant load and still air. Tg is globe temperature; Tdb is dry-bulb (air) temperature.
Given Tnwb = 25.0°C, Tg = 33.0°C, Tdb = 30.0°C:
WBGT = 0.7 × 25.0 + 0.2 × 33.0 + 0.1 × 30.0
= 17.5 + 6.6 + 3.0
= 27.1°CReference thresholds from NIOSH 2016-106 Table 6-2, computed by the same calculator engine used on its full standard page:
Scenario: full sun exposure · 50% relative humidity
| WBGT (°C) | Light 180 W | Moderate 300 W | Heavy 415 W | Very heavy 520 W |
|---|---|---|---|---|
| 24 | 60 / 0 min work/rest per hr | 60 / 0 min work/rest per hr | 60 / 0 min work/rest per hr | 60 / 0 min work/rest per hr |
| 25 | 60 / 0 min work/rest per hr | 60 / 0 min work/rest per hr | 45 / 15 min work/rest per hr | 45 / 15 min work/rest per hr |
| 26 | 60 / 0 min work/rest per hr | 60 / 0 min work/rest per hr | 40 / 20 min work/rest per hr | 40 / 20 min work/rest per hr |
| 27 | 60 / 0 min work/rest per hr | 60 / 0 min work/rest per hr | 35 / 25 min work/rest per hr | 35 / 25 min work/rest per hr |
| 28 | 60 / 0 min work/rest per hr | 45 / 15 min work/rest per hr | 30 / 30 min work/rest per hr | 30 / 30 min work/rest per hr |
| 29 | 60 / 0 min work/rest per hr | 35 / 25 min work/rest per hr | 25 / 35 min work/rest per hr | 25 / 35 min work/rest per hr |
| 30 | 60 / 0 min work/rest per hr | 25 / 35 min work/rest per hr | 15 / 45 min work/rest per hr | 15 / 45 min work/rest per hr |
| 31 | 45 / 15 min work/rest per hr | 20 / 40 min work/rest per hr | Stop work | Stop work |
| 32 | 35 / 25 min work/rest per hr | Stop work | Stop work | Stop work |
| 33 | 15 / 45 min work/rest per hr | Stop work | Stop work | Stop work |
| 34 | Stop work | Stop work | Stop work | Stop work |
| 35 | Stop work | Stop work | Stop work | Stop work |
| 36 | Stop work | Stop work | Stop work | Stop work |
This standard's declared inputs do not include acclimatization status, so results do not vary by it.