On August 30, 2024, OSHA published its Notice of Proposed Rulemaking for Heat Injury and Illness Prevention in Outdoor and Indoor Work Settings — the first federal heat standard in US history. After a public hearing held from June 16 to July 2, 2025, and a post-hearing comment period that closed in October 2025, the rulemaking process is moving toward a final standard. For EHS managers, the question is no longer whether a federal heat standard is coming. It is whether your programme is ready for it.

What the proposed standard covers

The proposed rule would apply to all employers conducting outdoor and indoor work across general industry, construction, maritime, and agriculture — every sector where OSHA has jurisdiction. It covers roughly 36 million workers nationwide, making it one of the broadest proposed occupational health standards in OSHA's history.

The core obligations the standard would impose on employers are structured around a Heat Injury and Illness Prevention Plan (HIIPP), which each covered employer must develop and implement. The key requirements include:

Heat index thresholds that trigger action. The proposed standard introduces two trigger levels based on the heat index (a composite of air temperature and relative humidity). At the initial heat trigger of 80°F (27°C), employers must provide drinking water, rest breaks, and shade or cool spaces. At the high heat trigger of 90°F (32°C), additional requirements activate: mandatory rest breaks of at least 15 minutes every two hours, an effective means of observing employees for signs of heat illness, and a buddy system or supervisory check-in.

Acclimatisation protocols. The standard specifically addresses new and returning workers — those in their first 14 days on a job with heat exposure — who face the highest risk. Employers would be required to limit heat exposure and monitor these workers more closely during the acclimatisation window.

Training. Both workers and supervisors must be trained on heat illness recognition, prevention measures, and emergency response procedures. Training must occur before employees work in heat conditions and must be refreshed as needed.

Emergency response procedures. Employers must have a written plan for responding to suspected heat illness, including how to contact emergency services and what to do while waiting for them.

The current enforcement landscape

Even before the final standard is published, OSHA is actively enforcing heat-related hazards. The agency established a National Emphasis Program (NEP) on Outdoor and Indoor Heat-Related Hazards in 2022 — still in effect as of 2026 — under which it has conducted nearly 7,000 inspections and issued heat citations. Employers remain exposed under the General Duty Clause, which requires workplaces to be free from recognised serious hazards.

The BLS data makes the stakes clear. Exposure to environmental heat resulted in 48 work-related deaths in the US in 2024, with 7,100 recorded injury and illness cases in 2023-2024. These figures are widely regarded as significant underestimates: OSHA estimates that heat illness statistics undercount real cases by a substantial margin, partly because symptoms overlap with other medical conditions and partly because many cases go unreported. From 1992 to 2021, heat killed 999 US workers — nearly 1,000 preventable deaths over three decades with no specific federal standard in place.

Construction workers, agricultural workers, and foundry and warehouse employees carry the highest burden.

What the regulation does not address: the emergency treatment gap

The proposed standard is a prevention framework. It addresses triggers, rest breaks, water access, training, and acclimatisation. It does not specify what employers must do when a worker presents with suspected exertional heat stroke despite these measures.

This gap matters because exertional heat stroke — where core body temperature rises above 40°C — can develop even when prevention protocols are in place. A young, fit, and acclimatised worker on a roofing crew can collapse. A warehouse supervisor in good health can deteriorate rapidly on the floor. When it happens, the outcome depends almost entirely on what occurs in the first 30 minutes.

The ACSM Expert Consensus Statement 2023 and the Korey Stringer Institute (Dr Douglas Casa, UConn) are unambiguous: the target is to reduce core temperature below 40°C within 30 minutes of collapse. Cold water immersion achieves a cooling rate of 0.35°C per minute — ten times faster than wet towels or ice packs applied to the skin. On 401 documented cases treated with immediate immersion, the survival rate was 100%.

For EHS managers building a heat illness programme that is both regulation-ready and clinically sound, the plan needs two distinct components: a prevention layer (what the OSHA standard addresses) and an emergency treatment layer (what it does not). The emergency layer means having a means of cold water immersion available on site, with staff trained to deploy it before EMS arrives — particularly on remote or semi-rural sites where response times can exceed 20 minutes.

Kollder is a portable emergency cooling tub that deploys in under 30 seconds by one person, on any surface, and allows full patient access during immersion. For EHS teams working to close the gap between prevention and emergency response, more information is available at kollder.com/#contact.

What to do now

The final OSHA heat standard is not yet published, but the regulatory direction is set. EHS managers who wait for the final rule before acting will be scrambling during peak heat season. The steps that are defensible now — and that align with the proposed requirements — include:

Conduct a heat hazard assessment of all indoor and outdoor work areas before summer, documenting which roles, locations, and times of day carry the highest exposure. This assessment forms the basis of your HIIPP whether or not a final rule is in place.

Review your acclimatisation programme. The first 14 days of heat exposure are where the data consistently shows elevated risk. New hires, seasonal workers, and employees returning from extended leave all require graduated exposure.

Train supervisors to recognise early signs of heat illness — confusion, coordination loss, cessation of sweating in hot conditions, unusual behaviour — and to act immediately. Training that focuses only on hydration and rest misses the critical recognition component.

Document your emergency response procedure in writing. Identify the nearest hospital equipped for heat stroke management, confirm EMS contact information for each site, and establish what cooling resources are available on site between the time of collapse and EMS arrival.

Further reading

Sources: OSHA, Notice of Proposed Rulemaking — Heat Injury and Illness Prevention in Outdoor and Indoor Work Settings, Federal Register, August 30, 2024, federalregister.gov/d/2024-14824 — OSHA Heat Injury and Illness Prevention Rulemaking, osha.gov/heat-exposure/rulemaking — Bureau of Labor Statistics, Census of Fatal Occupational Injuries 2024, injuryfacts.nsc.org — ACSM Expert Consensus Statement 2023 — Casa DJ et al., Exercise and Sport Sciences Reviews 2007 — Korey Stringer Institute, University of Connecticut

Kollder is the emergency cooling tub that deploys in under 2 minutes, anywhere.

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