Heat rules in Maryland: COMAR 09.12.32, in effect September 30, 2024

This page reports what the official source says. It is not legal advice: ask the office named here. It restates Maryland Code of Regulations chapter 09.12.32, as published by the Maryland Division of State Documents, and the Maryland Occupational Safety and Health (MOSH) heat stress page, as read on October 8, 2026. MOSH says the standard went into effect on September 30, 2024. The comparison of every place is on the heat rules overview.

Scope and trigger

Regulation .02 applies to an employer whose employees work, indoors or outdoors, where the heat index equals or exceeds 80 degrees Fahrenheit. It does not apply to emergency operations and essential services (the definition includes emergency restoration of essential utilities), to incidental exposures when an employee is not required to work more than 15 consecutive minutes per hour, or to buildings, structures and vehicles where mechanical ventilation or a fan keeps the heat index below 80 degrees. High-heat conditions are defined as a heat index of 90 degrees Fahrenheit or above. The heat index is the measure that combines air temperature and relative humidity, which the regulation says can be taken from the National Weather Service calculator.

What the chapter requires

Regulation	What it says
.04 Plan	The employer monitors the heat index through the work shift by direct measurement, by National Weather Service data or by the NIOSH Heat Safety Tool app, and keeps a written heat-related illness prevention and management plan with 13 listed elements, available to employees and to MOSH on request
.05 Acclimatization	Up to 14 days for an employee newly exposed to heat or returning after 7 or more consecutive days of absence, with monitoring by phone or radio, a buddy system or other observation, and a written schedule
.06 Shade	Shaded areas as close to the work area as practicable, outside, open and exposed to air on at least three sides, sized for the people using them, allowing sitting in normal posture and the removal and storage of protective equipment; alternative cooling measures with equivalent protection if outdoor shade is demonstrably infeasible or unsafe
.07 Water	Drinking water at no cost as close to the work area as practicable, with at least 32 ounces per hour available to each exposed employee
.08 High heat	At a heat index of 90 degrees Fahrenheit or above: a minimum rest period of 10 minutes for every 2 hours worked above 90 and below 100, and 15 minutes for every hour above 100, or the NIOSH work-rest recommendations; rests taken in shade; monitoring of exposed employees; procedures in writing in a language employees understand. The schedule may be set aside if the employer shows effective protection through alternative cooling measures documented in writing
.09 Emergency response	Communication that lets an employee reach a supervisor or emergency medical services, response to signs of heat-related illness, care for those showing symptoms, and contact with emergency medical services and transport if necessary
.10 Training	Before first exposure, annually, and immediately after any suspected or confirmed heat-related illness at the worksite, with records kept for one year and available to MOSH

What MOSH adds

The MOSH heat stress page says the standard applies to all workplaces where the heat index is 80 degrees Fahrenheit or higher, and lists outdoor laborers and construction among the occupations at particular risk. It links a summary of key requirements and an optional model program for employers. MOSH says it is developing more guidance.

Heat rules in Maryland: COMAR 09.12.32, in effect September 30, 2024

Scope and trigger

What the chapter requires

What MOSH adds

Sources