Who could be affected by heat? Workers exposed to hot indoor environments or hot and humid conditions outdoors are at risk of heat-related illness, especially those doing heavy work tasks or using bulky or non-breathable protective clothing and equipment. Some workers might be at greater risk than others if they have not built up a tolerance to hot conditions, or if they have certain health conditions. The table below shows some environmental and job-specific factors that increase the risk of heat-related illness. Factors That Put Workers at Greater Risk: (1) Environmental: (a) High temperature and humidity; (b) Radiant heat sources; (c) Contact with hot objects ; (d) Direct sun exposure (with no shade); (e) Limited air movement (no breeze, wind or ventilation). (2) Job-Specific: (a) Physical exertion; (b) Use of bulky or non-breathable protective clothing and equipment. Workers who are suddenly exposed to working in a hot environment face additional and generally avoidable hazards to their safety and health. New workers and those returning from time away are especially vulnerable. That's why it is important to prepare for the heat: educate workers about the dangers of heat, acclimatize workers, gradually increase the workload or allow more frequent breaks to help new workers and those returning to a job after time away build up a tolerance for hot conditions. (A) Heat Index (HI): Less than 91°F; Risk Level (RL): Lower (Caution); Protective Measures (PM): Basic heat safety and planning. (B) (HI): 91°F to 103°F; (RL): Moderate; (PM): Implement precautions and heighten awareness. (C) (HI): 103°F to 115°F; (RL): High; (PM): Additional precautions to protect workers. (D) (HI): Greater than 115°F; (RL): Very High to Extreme; (PM): Triggers even more aggressive protective measures. See more from topic source: https://www.osha.gov/html/a-z-index.html.