Heat Stress

In mining, exposure of workers to very hot conditions is unhealthy and unproductive. High or moderately high levels of work produce a great deal of heat in the body, resulting in heat stress.

Heat stress is caused by high air temperatures, high humidity, and relatively low air movement. Heat stress can cause a number of symptoms:

• Dizziness
• Faintness
• Breathlessness
• Palpitations
• Extreme thirst

Heat tolerance is dependent on hydration and on maintaining a balanced diet. For proper hydration, workers should drink enough water or other appropriate drinks. MSHA recommends drinking a cup of water every 15 to 20 minutes when working in hot environments. Workers should avoid drinks that contain carbonation, sugar, salt, or caffeine. Other practices that miners can implement to avoid heat stress include the following:

• Adopt a work-rest regimen that includes frequent breaks and reasonably short work periods
• Pace tasks reasonably
• Perform heavy tasks in cooler areas or at cooler times

Mine operators can adopt the following practices to ensure the health and safety of their miners:

• Rotate personnel on hot jobs
• Provide readily accessible, cooler rest areas and cool drinking water that is 50 degrees to 60 degrees Fahrenheit (10 degrees to 15 degrees Centigrade)
• Encourage all workers to drink a cup of water every 15 to 20 minutes
• Reduce individual workloads by providing proper tools and task-sharing

To learn more about MSHA Part 48 training requirements visit our MSHA Part 48 Subpart B Surface Mining Online Training web page.