Construction is often associated with outdoor heat, but many employees also work in enclosed or partially enclosed areas where heat can build rapidly. Interior renovation, mechanical rooms, warehouses, temporary structures, enclosed floors, and buildings without operating ventilation can create indoor heat hazards.

California’s indoor heat illness prevention regulation generally applies to covered indoor workplaces when the indoor temperature reaches 82 degrees Fahrenheit. Construction employers should evaluate whether a work area is considered indoors and whether an exception applies rather than assuming all project work falls under the outdoor standard.

What may count as an indoor construction work area
An indoor area may include a building or room enclosed by walls and a ceiling, even when doors or windows are open. Work inside a structure under construction can become especially hot when permanent HVAC systems are not operating, radiant heat enters through roofing or glazing, or heat- producing tools are used.

Because project conditions evolve, a work area may shift from outdoor to indoor or may involve both standards at different times. The employer’s planning should reflect the actual environment where employees perform their tasks.

Basic prevention measures
Covered employers should provide drinking water, access to cool-down areas, and preventive cool-down rest periods. Supervisors must allow and encourage workers who feel the need to cool down to take a rest in the designated area and should monitor them for symptoms.

The cool-down area should be shielded from direct sunlight and maintained at a temperature below 82 degrees Fahrenheit unless an exception applies. It should also be large enough to accommodate employees taking recovery or rest periods.

Assessment and control of indoor heat
Employers should have a dependable method for measuring temperature and, when applicable, heat index. A written plan should identify who conducts measurements, when measurements are repeated, what records are kept, and what actions are triggered by the results.

Controls may include increased ventilation, fans or air conditioning where appropriate, local exhaust, insulation or shielding of radiant heat sources, changes in work practices, additional breaks, scheduling heavy work for cooler times, and reducing the use of heat-retaining clothing where safely possible.

Training and emergency planning
Workers should be trained to recognize early symptoms such as headache, dizziness, weakness, nausea, heavy sweating, confusion, and unusual behavior. Supervisors need clear instructions for responding to symptoms and contacting emergency medical services.

Indoor heat planning should be coordinated with the company’s IIPP, emergency procedures, and site-specific safety plan. It should also address subcontractors and temporary employees who may not be familiar with the building or available cooling areas.

How EA Safety Services can help
EA Safety Services, LLC can assess enclosed work areas, help determine which heat procedures apply, review temperature-monitoring practices, and develop a written indoor heat illness prevention plan tailored to the project.