Preliminary compliance estimate — NOT a substitute for a Competent Person, code official (AHJ), or licensed professional. Heat stress hazards are enforced under OSH Act General Duty Clause § 5(a)(1) using NWS Heat Index guidelines.
Heat Index & Work/Rest Safety Calculator
Calculate jobsite Heat Index using the exact NWS Rothfusz regression polynomial and evaluate NIOSH work/rest controls.
Ambient Air & Humidity Inputs
Heat Risk Dashboard
Danger LevelNWS Heat Index Risk Band Spectrum
Frequently Asked Questions (FAQ)
What is the OSHA Heat Index threshold for initiating heat safety precautions?
OSHA defines a Heat Index of 80°F (27°C) to 90°F (32°C) as Caution level, requiring access to fresh water and shaded rest areas.
What are the OSHA Heat Index risk category levels?
Caution (80-90°F), Moderate (90-103°F), High (103-115°F), and Very High/Extreme (> 115°F), each triggering mandatory work/rest cycles.
What is WBGT (Wet Bulb Globe Temperature) and how does it differ from Heat Index?
WBGT measures heat stress factoring in air temperature, humidity, wind speed, and direct solar radiant heat, making it superior for outdoor solar site assessments.
What water intake volume is recommended for outdoor construction workers in high heat?
OSHA recommends workers drink 1 cup (8 oz) of cool water every 15 to 20 minutes in hot environments, rather than drinking large amounts infrequently.
What is worker heat acclimatization and how long does it take?
Acclimatization is building heat tolerance. OSHA recommends a 5-day ramp-up schedule for new or returning workers: 20% exposure Day 1, increasing 20% each day.
What are the signs of Heat Exhaustion vs dangerous Heat Stroke?
Heat Exhaustion includes heavy sweating, dizziness, nausea, and rapid pulse. Heat Stroke is a medical emergency with confusion, loss of consciousness, high body temp (> 104°F), and hot dry skin.
What rest break schedule is recommended under High Heat Index (> 103°F)?
Under High risk (103-115°F), OSHA/NIOSH guidelines specify 15 to 30 minutes of rest in shaded or air-conditioned areas for every 45 minutes of work.
How does high humidity impair human body cooling?
Sweat cooling relies on evaporation. High relative humidity prevents sweat from evaporating, trapping body heat and rapidly elevating core temperature.
What role do electrolytes play during heavy sweating in hot environments?
Heavy sweating depletes sodium and potassium. For work lasting longer than 2 hours, electrolyte-replenishing beverages should supplement plain drinking water.
What emergency response steps should be taken if a worker shows signs of Heat Stroke?
Call 911 immediately, move worker to shade, cool body with cold water/ice packs on neck, armpits, and groin, and do NOT force liquid if unconscious.