646 Heat Injury and Illness Prevention: Supervisor

Maryland Requirements

Application & Scope

This section supplements OSHAcademy Course 646: Heat Injury and Illness Prevention (Supervisor) and is designed to align the training with the Maryland Department of Labor's (MDOL) Heat Stress Standards, effective September 30, 2024. For more in-depth review or questions about the standards please click on the link below:

• COMAR 09.12.32 – Chapter 32 Heat Stress Standards

When the Standards Apply

This rule covers all Maryland workplaces (inside and outside) where workers could face a heat index of 80°F or higher. It does not apply to:

• Emergency operations (law enforcement, EMS, firefighting, rescue, evacuation, or emergency restoration of essential utilities or telecommunications)
• Incidental exposures under 15 minutes per hour
• Workplaces with mechanical ventilation that keeps the heat index below 80°F

Heat-Related Illness Prevention and Management Plan

Employers must monitor the heat index throughout the work shift in areas where employees are working, using one of the following methods:

• Direct measurement of temperature and humidity at the same time and location where employees are working
• Use of local weather data reported by the National Weather Service or another recognized source to determine the heat index
• Use of the National Institute for Occupational Safety and Health (NIOSH) Heat Safety Tool application to determine the heat index.

Acclimatization

Employers must provide acclimatization for up to 14 days:

• Applies to newly exposed workers and those returning after 7+ days off work.
• Employers must monitor workers during this period using regular communication (phone or radio), a buddy system, or other effective means of observation.
• The acclimatization schedule must be in writing and can follow:
  • A gradual exposure plan over a 5-14 day period (max 20% increase in exposure per day)
  • NIOSH recommendations
  • A combination of gradual exposure and alternative cooling measures
• The acclimatization schedule shall consider the following elements:
  • Acclimated and unacclimated employees
  • Environmental conditions and anticipated workload
  • The impact of required clothing and personal protective equipment on the heat burden of employees
  • Personal risk factors that place an employee at higher risk of heat-related illness
  • Re-acclimatizing employees as necessary
  • The use of alternative cooling and control measures

Shade Access

Employers must provide shaded areas:

• Located as close as practicable to work areas.
• Must be open and exposed on three sides, free of added heat sources, and large enough for workers to sit comfortably.
• Must allow removal of PPE during use.
• If outdoor shade is infeasible, employers must provide alternative cooling and control measures (e.g., mechanical ventilation, misting fans, cooling garments).
• Indoor cooling areas must meet the same ventilation and capacity requirements

Drinking Water

Employers must:

• Provide cool, potable water at no cost, as close to the work area as practicable
• Make available at least 32 ounces per hour per employee, ensuring access throughout the shift (does not all need to be supplied at the start)

High-Heat Procedures

Triggered when the heat index ≥ 90°F:

• Employers must implement work/rest schedules that account for heat, workload, and PPE
• Unless alternative cooling controls are used, the minimum rest requirements are:
  • 10 minutes rest for every 2 hours worked (90–100°F)
  • 15 minutes rest for every hour worked (>100°F)
  • Alternatively, employers may adopt a work/rest schedule consistent with current NIOSH recommendations.
• Rest must occur in shaded areas and may coincide with normal breaks
• Employers may not discourage rest
• Workers must be monitored via phone, radio, buddy system, or other effective means of observation during high-heat operations
• Procedures must be written and available in a language workers understand

Emergency Response

Employers must maintain an emergency response plan including:

• Effective, reliable and accessible communication systems (voice, radio, or electronic)
• Procedures to monitor, respond, and provide care for symptomatic employees
• EMS contact and transport procedures ensuring responders can reach the affected worker

Training

Employers must provide initial and annual training prior to heat exposure ≥ 80°F—and retraining after any heat-related illness incident—for all employees and supervisors. Training must be in a language and manner understandable to employees and include:

• Environmental and personal risk factors
• Importance of acclimatization
• Importance of hydration and rest breaks
• Types, signs, and symptoms of heat illness
• First aid and emergency response
• Reporting procedures
• Employer's specific plan and requirements under COMAR 09.12.32. Training records must include:
  • names of the students
  • date of the training session
  • a summary of the training content
  • kept for one year
  • available to MOSH upon request

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