For PHEL Curves 1-3, which conditions apply?

• A. Watch/work length <4 hours & space >=100 °F OR Watch/work length >4 hours & space >=90 °F.
• B. Watch/work length <6 hours & space >=80 °F OR watch/work length >6 hours & space >=85 °F.
• C. Watch/work length <2 hours & space >=110 °F OR watch/work length >2 hours & space >=95 °F.
• D. Space temperature is irrelevant to PHEL Curves 1-3.

Answer: (A)

PHEL curves show how heat exposure limits depend on how long you’re exposed. The longer you work, the cooler the space needs to be; shorter tasks can tolerate a hotter space. The choice that follows this pattern says: if the watch/work length is less than four hours, the space temperature is allowed to be as high as 100 °F or more; if the length is more than four hours, the space temperature should be at least 90 °F. This aligns with the idea that shorter durations permit higher temperatures, while longer durations require cooler conditions. The other options don’t fit that time–temperature relationship, or claim the space temperature doesn’t matter, which isn’t correct for these curves.