The First Federal Heat Standard Is Coming — Is Your Indoor Warehouse Ready?

For the first time in its history, OSHA is moving toward a nationwide rule built specifically around heat. On August 30, 2024, OSHA published in the Federal Register a Notice of Proposed Rulemaking for Heat Injury and Illness Prevention in Outdoor and Indoor Work Settings — a significant step toward a federal heat standard that would apply to all employers conducting outdoor and indoor work in all general industry, construction, maritime, and agriculture sectors where OSHA has jurisdiction.¹ The rule is sweeping in reach: it is a comprehensive framework designed to protect approximately 36 million workers in both indoor and outdoor settings.²

Crucially, the term "indoor" is not an afterthought — it is in the title. Warehouses, distribution centers, and manufacturing floors fall directly within scope, and the risk is real. Facilities such as warehouses and factories rarely have air conditioning, and equipment like furnaces and ovens can exacerbate the heat.³ The danger is not hypothetical for indoor workers: of the 20 workers known to have died on the job from heat stress between 2011 and 2018 in California, seven worked inside.⁴

The backbone of the standard is a written program. The proposed rule would require employers with 10 or more employees to develop a written heat injury and illness prevention plan (HIIPP), which must be reevaluated and reviewed at least annually, as well as each time a heat-related illness or injury results in loss of consciousness, medical treatment beyond first aid, days away from work, or death.⁹ For indoor operators specifically, employers need to identify areas where the heat index may reach 80°F and incorporate a monitoring plan into their HIIPP.¹⁰ The plan must also designate at least one heat safety coordinator, with involvement of non-managerial employees and their representatives required.¹¹

The rule operates on two thresholds. At the "initial heat trigger," a heat index of at least 80°F, employers must ensure that employees have cool drinking water, cool break areas, paid rest breaks, and acclimatization protocols.⁹ The "high heat trigger" escalates obligations: at or above a heat index of 90°F, employers must provide mandatory rest breaks of 15 minutes at least every two hours, observation for signs and symptoms of heat-related illness, a hazard alert to remind employees of key parts of the HIIPP, and warning signs at indoor work areas with ambient temperatures that regularly exceed 120°F.¹²

Acclimatization is one of the most consequential — and most overlooked — provisions, because most heat tragedies happen to the newly exposed. OSHA heard that a majority of heat deaths occur in the first three days on the job; the draft therefore mandates phased work increases for new and returning workers.¹³ In practice, this means structured ramp-up. For workers who have been away from a hot environment for more than 14 days, the gradual acclimatization option involves 50% heat exposure the first day, 60% the second day, and 80% the third day.⁹ For a warehouse, this is concrete: if a worker will spend most of their time packing boxes in a hot warehouse, they should perform packing tasks from day one — but for 20% of their eventual workday.¹⁴

Training rounds out the obligations. Workers must be trained on recognizing heat hazards, signs and symptoms of heat illness, methods to control exposure, acclimatization practices, and emergency procedures.¹⁵ The state precedent shows this is workable: California already mandates that for most workplaces where the indoor temperature reaches 82°F, employers provide access to drinking water and cool-down areas, closely observe employees during acclimatization, train employees, and provide timely emergency aid.¹⁶

The procedural clock has nearly run out on the comment phase, and enforcement is already at record levels. Whether the standard is finalized this year or later, the components — a written HIIPP, a designated coordinator, indoor monitoring, acclimatization ramps, rest breaks, training, and clear visual cues — are well-defined and largely mirror existing state law. Building the program now, anchored by an ANSI-compliant signage system that turns 80°F and 90°F triggers into floor-level action, is the lowest-risk path forward.