While Texas has given us a break with relatively mild temperatures this summer, the forecast shows we’re about to enter the real heat of the season. With several months of intense weather ahead, now is the perfect time to refresh your heat stress prevention strategies.

As your EHS partner, we want to ensure your team stays safe and productive during these challenging conditions. Heat-related illnesses are 100% preventable when proper precautions are in place – and that’s exactly what we’re here to help you achieve.

What You Need to Know About Heat Stress Regulations

You may remember our communication last July about OSHA’s proposed Heat Stress Standard. While that complex regulation never became law and is unlikely to move forward under the current administration, this doesn’t mean employers are off the hook.

Here’s the reality: OSHA actively enforces heat stress protections through the General Duty Clause, which references standards established by the ACGIH (American Conference of Governmental Industrial Hygienists). Bottom line – you’re still required to protect your workers from heat-related hazards.

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Your Action Plan: Key Heat Stress Prevention Essentials

While the complete ACGIH guidance provides comprehensive details, here are the critical elements every employer must implement:

The general control recommendations are typically categorized into engineering controls, administrative controls, and personal protective equipment (PPE), with engineering controls being the most effective and preferred.

  1. Engineering Controls (Most Effective): Engineering controls aim to modify the work environment to reduce the heat load on workers. These are the primary and most effective methods for preventing heat stress.
  • Reduce Air Temperature and Humidity:
    • General Ventilation: Dilute hot air with cooler outside air. This is more effective in cooler climates.
    • Air Conditioning/Air Cooling: Install systems to actively cool the air and, in some cases, remove humidity. Localized air conditioning or “cool rooms” can be used for specific workstations or recovery areas.
    • Dehumidification: Eliminate sources of humidity (e.g., open hot water baths, leaky steam valves) and use dehumidifiers (Source 1.6, 2.2).
  • Increase Air Movement (Convection):
    • Fans: Use general or spot cooling fans to increase air speed around workers. This enhances convective heat exchange and sweat evaporation, especially when air temperature is below skin temperature (approx. 35°C or 95°F) (Source 1.6, 2.2).
  • Reduce Radiant Heat:
    • Insulation: Insulate hot surfaces (e.g., furnace walls, hot pipes) to prevent heat from radiating into the workspace (Source 1.1, 1.6, 2.2).
    • Reflective Shields/Barriers: Use reflective barriers, screens, or aprons to block radiant heat sources or shield workers from them. Flat black surfaces absorb more heat, so reflective or shiny paints can be used on hot surfaces (Source 1.1, 1.6, 2.2).
    • Remote Controls/Mechanization: Use remote controls or mechanize tasks to remove workers from direct exposure to heat sources (Source 1.6).
  1. Administrative Controls: Administrative controls involve changes to work practices and schedules to limit worker exposure to heat. These are implemented when engineering controls are not sufficient.
  • Acclimatization Program:
    • Implement a structured program to gradually adapt workers to hot environments. This is crucial for new workers and those returning after an extended absence from heat exposure (typically 7-14 days for new workers, 2-4 days for returning workers) (Source 1.1, 1.5).
    • **(Since a high percentage of heat stress illnesses and fatalities impact new employees who haven’t been properly acclimated to heat, we have included a deep dive review of ACGIH acclimatization recommendations below)**
  • Work-Rest Regimen:
    • Establish appropriate work-rest schedules that vary based on environmental heat (Wet Bulb Globe Temperature – WBGT) and workload (light, moderate, heavy). As heat stress increases, work periods should shorten, and rest periods in cool areas should lengthen (Source 1.1, 1.3, 1.6, 2.2).
    • Encourage workers to set their own pace and take rest breaks as needed (Source 2.1).
  • Scheduling Work:
    • Reschedule strenuous or hot work to cooler times of the day (e.g., early morning, late afternoon, or evening) or cooler seasons of the year (Source 1.1, 2.1, 2.5).
  • Hydration Program:
    • Ensure easy access to cool (10-15°C or 50-60°F) drinking water.
    • Encourage frequent fluid intake (e.g., 250 ml or one cup every 15-20 minutes), even if workers don’t feel thirsty, to replace fluid loss from sweating.
    • Avoid caffeinated, sugary, or alcoholic beverages. Sports drinks may be beneficial for very physically active occupations but should be used in moderation (Source 1.1, 2.1, 2.5).
  • Job Rotation/Relief Workers:
    • Rotate workers through different tasks or provide relief workers to reduce individual heat exposure and exertion levels (Source 1.1, 2.1, 2.5).
  • Training and Education:
    • Provide comprehensive training to both workers and supervisors on:
      • Recognizing heat stress symptoms (for themselves and co-workers).
      • Prevention strategies (hydration, work-rest cycles).
      • First aid for heat-related illnesses.
      • Understanding personal risk factors (Source 1.1, 1.7, 2.1).
  • Buddy System:
    • Implement a buddy system where co-workers monitor each other for signs of heat stress, as individuals may not recognize their own symptoms (Source 1.1, 2.1).
  • Emergency Response Plan:
    • Develop and implement an emergency plan for heat-related illnesses, including procedures for providing first aid and accessing medical care (Source 2.1, 2.4).
  • Medical Monitoring Program:
    • For more robust programs, establish medical monitoring, including pre-placement and periodic medical evaluations, and on-the-job monitoring (e.g., core temperature, heart rate, hydration status) for workers in high-risk environments (Source 1.1, 1.3, 1.6, 2.5).

III. Personal Protective Equipment (PPE): PPE is the least preferred control method and should only be used as a supplement when engineering and administrative controls are insufficient or not feasible. It’s important to note that some PPE can increase heat burden.

  • Appropriate Clothing:
    • Encourage wearing light-colored, loose-fitting clothing that permits sweat evaporation.
    • Consider clothing adjustment factors when using WBGT, as impermeable or multi-layered clothing can significantly reduce heat loss (Source 1.5, 1.6, 4.3).
  • Auxiliary Body Cooling Systems:
    • For extreme conditions or specific tasks, specialized cooling garments can be used:
      • Water-cooled garments: Circulate cool water close to the body.
      • Air-cooled garments: Circulate cool air over the body.
      • Cooling vests/ice-packet vests: Contain ice packs or cooling gels (Source 1.1, 1.6, 2.2, 2.4, 2.5, 4.1).
      • Wetted over-garments: Provide evaporative cooling (Source 1.1, 1.6).
  • Head and Face Protection:
    • Sun hats or wide-brimmed hats for outdoor work (Source 1.1, 1.6).
    • Infrared-reflecting face shields (Source 2.4).
  • Sunscreen: For outdoor workers to protect against solar radiation (Source 1.1, 1.6).

The ACGIH guidelines emphasize that a comprehensive heat stress management program should integrate these control measures, along with a thorough assessment of the work environment (using tools like WBGT) and individual worker factors.

 

  • Acclimatization:
    • Definition: Acclimatization is a gradual physiological adaptation that enhances an individual’s tolerance to heat stress. It requires physical activity under heat-stress conditions similar to those anticipated for the actual work (Source 1.4).
    • Acclimatization Schedule:
  • Gradual Increase: The core principle is a gradual increase in exposure time and workload in hot conditions over a period of days. The environment and exposures should be stressful enough to induce profuse sweating and elevated body temperatures, but not to the point of heat exhaustion (Source 3.1).
  • New Workers: For workers new to a hot environment, the recommended schedule is:
    • No more than 20% exposure on Day 1.
    • An increase of no more than 20% on each additional day thereafter (Source 1.2).
    • Full acclimatization can take 7 to 14 days (Source 1.2, 3.1). A slower, more conservative approach is generally preferred (Source 3.1).
  • Returning Workers (Previous Experience): For workers who have had previous experience with the job but have been away from heat exposure for a period:
    • No more than 50% exposure on Day 1.
    • 60% on Day 2.
    • 80% on Day 3.
    • 100% on Day 4 (Source 1.2).
  • Individual Factors: The level of acclimatization achieved is relative to an individual’s initial physical fitness and the total heat stress experienced. Less physically fit workers or those with underlying health conditions may require longer acclimatization periods (Source 1.2, 3.1).
  • Maintaining and Losing Acclimatization:
  • Maintenance: Workers can generally maintain their acclimatization even if they are away from the job for a few days (e.g., over a weekend). However, if they are absent for a week or more, there may be a significant loss of the beneficial adaptations (Source 1.2, 3.1).
  • Loss: A noticeable decline in acclimatization occurs after four days away from heat exposure, and it may be completely lost in three to four weeks (Source 1.4, 1.5).
  • Re-acclimatization: If acclimatization is lost, it can often be regained in 2 to 3 days upon returning to a hot job, particularly for those who are physically fit (Source 1.2)

Key Considerations During Acclimatization:

  • Hydration: Proper hydration is crucial throughout the acclimatization process. Workers should drink plenty of cool water regularly, even if they don’t feel thirsty (e.g., 250 ml every 20 minutes) (Source 1.1, 3.1).
  • Monitoring: Monitor workers for signs and symptoms of heat-related illness, especially during the initial days of exposure. A “buddy system” is recommended as individuals may not notice their own symptoms (Source 1.1).
  • Work-Rest Regimen: Establish appropriate work-rest cycles that gradually increase work duration and intensity while ensuring adequate recovery (Source 1.1, 1.3).
  • Sudden Heat Increases: Acclimatization is specific to the level of heat stress exposure. A sudden, higher level of heat (e.g., during a heat wave) may not be fully acclimatized to, requiring extra caution (Source 1.4, 3.1).
  • Health Status: Workers with medical conditions, those taking certain medications, or older workers may have a decreased ability to sweat or tolerate heat and require special consideration or longer acclimatization periods (Source 1.1, 1.3, 3.1).