State compliance guide · Updated April 2026

Maryland Heat Standard (MOSH 2024)

Short answer: Maryland's MOSH heat rule (effective Sept 30, 2024) covers both indoor and outdoor workplaces. Initial trigger at heat index 80°F, high-heat at 90°F. Written plan required.

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At a glance

Maryland's heat triggers.

80°F

Initial trigger

Heat index at or above 80°F triggers water, shade/cool-down access, training, and acclimatization protocols.

90°F

High-heat trigger

Enhanced protections at 90°F+ heat index, including stricter rest and observation requirements.

Indoor + outdoor

Full coverage

One of the first eastern US states to cover indoor workplaces — warehouses, manufacturing, distribution.

Sept 2024

Effective date

MOSH heat illness prevention standard adopted and enforceable as of September 30, 2024.

Where cooling vests fit

Supplemental PPE under Maryland's MOSH plan.

Maryland requires water, shade, training, and acclimatization first. Active cooling vests are supplemental PPE that extend safe productive time during 80°F+ and 90°F+ trigger conditions — without competing with the required infrastructure.

IndoorWarehouses without HVAC are now squarely in scope.
OutdoorConstruction, utility, landscaping crews covered.
8–12 hrClemaCore covers full Maryland summer shifts without ice.
PPE-fitWorn under hi-vis, FR, and arc-rated outerwear.
DocumentedListed as PPE in your written MOSH plan.

FAQ

Maryland MOSH heat standard: employer FAQ.

What is the Maryland heat standard?

Maryland's heat illness prevention standard is enforced by the Maryland Occupational Safety and Health (MOSH) program and became effective September 30, 2024. It covers both indoor and outdoor workplaces and is among the first comprehensive state-level heat standards in the eastern United States.

At what temperature does Maryland's heat standard apply?

Maryland's MOSH rule uses a heat index approach: initial protections trigger at a heat index of 80°F, with enhanced high-heat requirements at a heat index of 90°F.

Does Maryland's heat standard cover indoor workers?

Yes. Unlike many state heat rules that apply only to outdoor work, MOSH covers both outdoor and indoor workplaces — making it directly applicable to warehouses, distribution centers, manufacturing facilities, and other indoor environments.

What does Maryland's heat illness prevention plan require?

Covered employers must develop a written heat illness prevention plan including hazard evaluation, water and shade/cool-down access, acclimatization for new workers, training, and emergency response procedures.

Do cooling vests count for Maryland heat compliance?

Cooling vests are supplemental PPE that support a compliant Maryland heat illness prevention plan. They do not replace required water, shade, training, or acclimatization, but they extend safe productive time during heat-index trigger periods. See our cooling vest comparison.

Maryland Heat Standard (MOSH 2024)

Maryland's heat triggers.

Supplemental PPE under Maryland's MOSH plan.

Maryland MOSH heat standard: employer FAQ.

Keep reading.

Federal OSHA Heat Standard

Cal/OSHA Heat Standard

Cooling Vest Types Compared

Build cooling vests into your MOSH plan.