Building a Heat Illness Prevention Program That Works

Two workers on the same shift can face different heat loads. Radiant heat, clothing, and the individual all play a part, and a worker returning after time away may face a different level of risk than the person working beside them. When someone begins showing serious symptoms, the response has to happen quickly.

For EHS professionals, the job is to turn those variables into a program supervisors and employees can actually use.

The Occupational Safety and Health Administration (OSHA) has proposed a federal heat standard, but it has not been finalized. In the meantime, OSHA continues to address occupational heat through the General Duty Clause and its revised National Emphasis Program for outdoor and indoor heat-related hazards. For the person building the program, that guidance also provides a useful view of what an inspector will look for.

Start With What OSHA Is Looking For

There is currently no final federal OSHA heat-specific standard. OSHA published its proposed Heat Injury and Illness Prevention in Outdoor and Indoor Work Settings rule in August 2024, held an informal public hearing in June and July 2025, and closed the post-hearing comment period on October 30, 2025. OSHA's latest regulatory agenda entry lists a supplemental proposed rule for December 2026 and final action for October 2027. Those are target dates, and the proposed requirements may still change.

Heat is nevertheless a recognized occupational hazard, and OSHA can use Section 5(a)(1) of the Occupational Safety and Health Act, commonly called the General Duty Clause, when the required elements of a violation are established.

OSHA also issued a revised Heat National Emphasis Program on April 10, 2026, replacing the 2022 version. It remains in effect for up to five years unless canceled or replaced. Appendix I directs compliance officers to evaluate areas such as:

• whether a heat illness prevention program exists;
• how temperature and work exertion are monitored;
• access to cool water, hydration breaks, rest breaks, and shade;
• acclimatization of new and returning workers;
• administrative controls;
• employee and supervisor training; and
• whether employees and supervisors can explain how the program works.

That final point is worth attention. A heat program can be technically complete and still fail operationally. If the supervisor running the shift cannot explain when additional breaks begin, who is currently acclimatizing, what symptoms require escalation, or when work stops, the written program is not doing much work.

For an EHS manager reviewing an existing program, Appendix I can therefore function as a practical gap-assessment framework.

Understand the Enforcement Context

OSHA's revised National Emphasis Program creates several pathways for heat conditions to receive enforcement attention. Programmed inspections may occur when the National Weather Service (NWS) has issued a heat advisory or warning for the local area, and the directive identifies a heat priority day when the expected heat index reaches 80°F.

Heat concerns can also arise during an inspection that began for another reason. Employee statements, injury and illness records, observed conditions, complaints, referrals, hospitalizations, or fatalities can bring heat into the scope of an inspection.

The practical point is simple: being outside a targeted industry list does not make occupational heat irrelevant. For EHS teams, the better question is whether employees are exposed and whether the organization has an effective way to manage that exposure.

Put Acclimatization Near the Top of the Program

If there is one part of a heat program worth reviewing before the next hot period, it is acclimatization.

OSHA's guidance on protecting new workers, citing a 2018 analysis by Tustin and colleagues, states that almost half of heat-related deaths occur on a worker's first day on the job or first day back after an extended absence, and more than 70 percent during the first week. Those numbers tell us where focused attention can have an outsized impact.

Acclimatization is the body's gradual adaptation to working in heat. For workers who are new to heat exposure, OSHA and the National Institute for Occupational Safety and Health (NIOSH) commonly recommend gradually increasing exposure using the 20 percent rule.

Reduce Duration, Not the Demands of the Job

The purpose of acclimatization is to gradually expose the worker to the conditions and work demands they will actually encounter.

For example, a new bricklayer should progressively perform bricklaying work in the heat rather than spend the entire acclimatization period doing unrelated light work in an air-conditioned area.

That creates an operational question EHS teams should solve before the worker arrives: what happens during the rest of the shift?

If the worker is limited to a portion of normal heat exposure on day one, alternate work needs to be planned. Without that plan, production pressure can gradually turn a shortened exposure into a normal shift. Acclimatization planning should therefore involve operations and supervision, not just EHS.

Programs should also account for workers returning after an extended absence, employees moving from climate-controlled work into hotter environments, and crews encountering a significant increase in heat compared with recent conditions.

Treat the 20 percent ramp as a starting structure, then adjust the plan for recent heat exposure, workload, PPE, and actual conditions.

Decide How You Will Measure Heat

One of the easiest ways to weaken a heat program is to use a measurement without being clear about what that measurement represents.

Three measures commonly appear in workplace programs:

Wet Bulb Globe Temperature is particularly useful when conditions involve factors that ordinary air temperature or heat index do not capture well. Clothing, PPE, workload, direct sun, radiant heat, and indoor process heat may all matter when evaluating actual worker exposure.

Forecasts and workplace measurements serve different purposes. A forecast helps an EHS manager or operations team plan tomorrow's staffing, work sequence, start time, or additional controls. A measurement at the work location helps a supervisor decide what needs to happen now.

Whatever method the organization chooses, define it in the program. Specify where measurements are taken, how often they are checked, who is responsible, and what happens when a trigger is reached. Record enough information to reconstruct the conditions later, including the value, location, time, and person taking the measurement.

Build Triggers That Produce Decisions

A trigger defines what changes when conditions reach a predetermined point. It should not require the supervisor to invent the response in the middle of a hot shift.

Every major heat trigger should define four things:

1. Threshold →
2. Location →
3. Owner →
4. Action

Threshold. What value or condition activates the trigger?

Location. Where is the condition measured or observed?

Owner. Who is responsible for checking it?

Action. What specifically changes when the trigger is reached?

For example, writing 'provide additional breaks during high heat' leaves an important decision to the supervisor. A stronger program defines the threshold, break frequency or duration, responsible person, and any additional controls that begin at the same time.

• water resupply;
• additional rest or cool-down breaks;
• acclimatization requirements;
• increased worker observation;
• active cooling measures;
• moving strenuous work into cooler parts of the shift;
• additional controls for PPE or radiant heat;
• stopping or postponing work; and
• escalating suspected heat illness to emergency response.

Where a state heat standard applies, its requirements need to be built directly into the program. Where no heat-specific state standard applies, OSHA and NIOSH guidance, the current National Emphasis Program, and the evolving federal rulemaking can help inform the program's structure.

Give Supervisors Authority to Use the Triggers

Triggers define the action. Authority determines whether the action actually happens.

The program should clearly state what supervisors are authorized to do when established conditions are reached. That may include increasing breaks, moving work, rotating employees, activating additional cooling, or stopping a task.

That authority should be discussed with operations before the season begins. Production pressure becomes much harder to manage when the first conversation about stopping work happens during the hottest shift of the year.

Training should also focus on what supervisors and employees may actually observe. Heat illness can develop through changes in physical condition, behavior, coordination, communication, or mental status. Employees should know which signs require the worker to stop, which require immediate escalation, and who initiates the emergency response.

The objective is not to turn supervisors into clinicians. It is to make sure they recognize when the situation has moved beyond routine heat controls and know what happens next.

Write the Emergency Procedure, Then Walk It

Heat emergencies are a poor place for improvisation.

A site-specific response should answer practical questions before an incident occurs:

• Who calls EMS, and who is the backup?
• Who remains with the affected worker?
• What cooling equipment is available and where is it located?
• What actions begin while EMS is responding?
• How will EMS enter the property and reach the exact work location?
• Who meets responders at the gate or entrance?
• How will the response work in remote or difficult-to-access areas?

The procedure should reflect current medical and emergency-response guidance for suspected serious heat illness, including the need for rapid cooling and prompt emergency medical attention.

Then test the procedure under realistic site conditions. Walk from the normal supervisor location to the most remote work area. Locate the cooling equipment. Confirm that employees can contact emergency services. Identify the correct gate or entrance. Determine who would meet responders.

The emergency plan written in the office may assume a three-minute response. A physical drill may reveal that retrieving equipment and reaching the work area takes eight. That is useful information to discover before someone needs it.

Verify the Program on the Floor

A heat program is only operational if the people using it can explain it. Field verification does not need to be complicated.

Ask a worker:

• Where is the drinking water and the nearest cooling or rest area?
• What changes when heat conditions become more severe?
• Who do you tell if you or a coworker begins to feel unwell?

Ask a supervisor:

• Who is acclimatizing today?
• What heat measure and trigger are we using?
• What action occurs when the trigger is reached?
• Can you modify or stop the work when the program requires it?
• How do you activate the emergency response?

If those answers are unclear, the problem is not solved by adding another paragraph to the written plan. Fix the part of the program that is not reaching the floor.

Bringing Heat Into Everyday Safety

A strong heat illness prevention program uses the same basic discipline as other EHS programs.

Identify who is exposed and understand the work being performed. Choose an appropriate way to evaluate conditions. Establish controls and clear action thresholds. Assign responsibility and authority. Train the people performing and supervising the work. Prepare for foreseeable emergencies. Then verify that what was designed on paper is actually happening in the field.

Heat adds another important consideration through acclimatization, particularly for new and returning workers.

The absence of a final federal heat standard does not prevent an EHS team from building a structured program. OSHA's current enforcement guidance, NIOSH recommendations, applicable state requirements, weather information, workplace measurements, and knowledge of the operation provide a basis for informed decisions now.

The objective is not simply to have a heat plan. It is to make the right response predictable before conditions become difficult.