National Geographic 260NE - Manual (Page 4)

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3.0 Heat Stress Index Scale
The Heat Index is a valuable measure of the affect of humidity on how “hot it
feels”. Since our bodies primary cooling mechanism is through perspiration and the
cooling effect of evaporation from our skin; as the humidity increases, there is less
evaporation and we feel hotter.
At a certain point, high Heat Index values become a health issue and a serious one
for people who are working or exercising in it. The color LCD scale reflects the Heat
Stress Index values and relates to the health affects outlined below:
IN RANGE OUT OF RANGE
Condition Temperature
Level Heat Index /
Humidex Value Physical Response
Cold Below 9.4°C/49°F
Cool 10°C to 20°C
50°F to 69°F
Comfort 21°C to 26°C
70°F to 79°F
Caution 27°C to 31°C
80°F to 89°F • Fatigue possible with
prolonged exposure and
physical activity
Extreme
Caution 32°C to 40°C
90°F to 104°F • Sunstroke, muscle cramps
and heat exhaustion are
possible with prolonged
exposure and physical
activity
Danger 41°C to 53°C
105°F to 129°F • Sunstroke, muscle cramps
and heat exhaustion are likely
• Heat stroke possible with
prolonged exposure and
physical activity
Extreme
Danger 54°C/130°F or
higher • Heat stroke and
sunstroke likely