1. What is Heat Index?

Definition: Heat Index (HI) measures how hot it feels when relative humidity is factored with air temperature.

Purpose: OSHA uses this to assess workplace heat stress risks and determine necessary precautions.

2. How Does the Calculator Work?

The calculator uses the NOAA/OSHA standard formula:

Where:

• \( HI \) — Heat Index (°F)
• \( T \) — Air Temperature (°F)
• \( R \) — Relative Humidity (%)
• \( c_1 \) to \( c_9 \) — Empirical coefficients

Note: Calculation is only valid when T ≥ 80°F and RH ≥ 40%

3. OSHA Heat Index Categories

Caution (80-90°F): Fatigue possible with prolonged exposure

Extreme Caution (91-103°F): Heat cramps, exhaustion possible

Danger (103-124°F): Heat cramps or exhaustion likely, heat stroke possible

Extreme Danger (≥125°F): Heat stroke highly likely

4. Using the Calculator

Tips: Enter current air temperature (°F) and relative humidity (%). Values must meet minimum thresholds.

5. Frequently Asked Questions (FAQ)

Q1: Why does OSHA use heat index?
A: It's the standard metric for assessing heat-related illness risks in workplaces.

Q2: What's the difference between heat index and "feels like" temperature?
A: They're essentially the same - both combine temperature and humidity.

Q3: How often should heat index be monitored?
A: OSHA recommends monitoring at least hourly during hot conditions.

Q4: What precautions should be taken at different HI levels?
A: OSHA requires increasing protective measures (water, rest, shade) as HI rises.

Q5: Does wind speed affect heat index?
A: The standard formula doesn't include wind, but breezes may make it feel cooler than calculated.