October 7, 2026
Maryland’s heat stress standard took effect on September 30, 2024. The Department of Labor’s MOSH guidance identifies an 80 degrees Fahrenheit heat-index trigger for covered indoor and outdoor workplaces under COMAR 09.12.32.
APT’s Maryland heat stress standard tracker record connects heat-index triggers with workplace coverage and protective procedures.
Heat index is the relevant trigger
MOSH describes monitoring through direct measurements, local weather data or the NIOSH Heat Safety Tool. A temperature reading without its humidity context does not by itself give the heat index used in the agency’s summary.
The agency identifies a written heat-related illness prevention and management plan, acclimatization, water, rest and training among the requirements. Its key-requirements guidance explains the core measures while directing employers to the regulation for full requirements.
Acclimatization is specifically relevant to workers newly exposed to heat and those returning after an absence of seven or more days. MOSH describes a written schedule, a period of up to 14 days, and close monitoring through observation or communication during that period.
Plan for the place and the workforce
APT’s practical interpretation is to connect the heat-index method with the actual work location and to identify who needs acclimatization when assignments change. A plan should explain how supervisors recognize the trigger, where workers obtain water and rest, and how the response is communicated.
The current scope provisions exclude specified emergency operations, qualifying incidental exposures of no more than 15 consecutive minutes per hour, and spaces kept below an 80°F heat index by effective mechanical ventilation or a fan. High-heat procedures begin at 90°F and include work/rest schedules and worker monitoring. The regulation provides specified rest schedules, a NIOSH schedule option and a documented alternative-controls provision; these conditions should be read before selecting a procedure.
Find related developments in the industrial hygiene regulatory tracker.
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