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OSHA & Compliance

OSHA Heat Rule Explained: What Employers Need to Know

OSHA's heat injury and illness prevention rulemaking has moved indoor and outdoor workplaces firmly into scope. This guide explains the rule in plain language, what employers must document, and the practical changes most small businesses need to make.

8 min read Updated June 15, 2026

On this page

  1. Who the rule covers
  2. Heat trigger thresholds
  3. The written Heat Illness Prevention Plan
  4. Training and supervisor duties
  5. Documentation inspectors look for

Who the rule covers

The standard applies to most general industry, construction, agriculture, and maritime employers where employees may be exposed to heat at or above defined trigger thresholds — indoors or outdoors. Office-only environments with consistent climate control are typically out of scope.

Heat trigger thresholds

Two thresholds drive employer obligations: an initial heat trigger (around 80°F heat index) and a high heat trigger (around 90°F heat index). Each unlocks specific controls — water, shade, rest, acclimatization, and monitoring.

The written Heat Illness Prevention Plan

Covered employers must maintain a site-specific written plan that identifies hazards, controls, responsibilities, training, and emergency response. The plan must be accessible to workers in a language they understand.

Training and supervisor duties

Workers and supervisors must be trained on heat illness signs, hydration, acclimatization, and how to report symptoms without retaliation. Supervisors carry specific monitoring duties during high heat conditions.

Documentation inspectors look for

Expect inspectors to ask for the written plan, training records, acclimatization schedules for new and returning workers, water and rest logs, and incident records. Missing documentation is the most common citation driver.

Frequently asked questions

Does the OSHA heat rule apply to indoor workplaces?
Yes. Indoor environments such as warehouses, kitchens, and manufacturing floors are in scope when temperatures reach the heat trigger thresholds.
Do small businesses need a written heat plan?
Yes. The written plan requirement applies regardless of employer size when workers are exposed at or above the heat triggers.
How long should heat-related records be kept?
Follow OSHA's general recordkeeping requirements — most heat-related training and incident records should be retained for the duration of employment plus the periods required by 29 CFR 1904.

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