Glen Kenny usually knows when someone is about to succumb to heat. He’s seen it a thousand times.
Workers may become less responsive than usual. They might struggle to stay focused on the task at hand, or forget to follow safety protocols. They might be short-tempered or aggressive when someone interrupts them. They might tell someone to back off, to leave them alone.
“Their body is under stress,” says Kenny, a professor of physiology at the University of Ottawa who studies the human heat stress response. “And for them, any voices, any distraction, that takes away their focus on themselves becomes an irritation for them. So you’re going to see irritability, you’re going to see loss of awareness of their surroundings, an inability to communicate effectively, all these become critical signs.”
The scary thing is, by the time an individual starts to feel unwell, they are already in the danger zone. Unlike strenuous exercise, heat stress is gradual. It builds, often without the individual noticing it—until all of a sudden, he or she does.