Acclimatization

Acclimatization is how the body adapts to heat after steady, gradual exposure. Sweating gets more efficient. NIOSH says employers should make sure workers are acclimatized before they work in a hot environment.

NIOSH advises building time in the heat over 7 to 14 days. For new workers, that means no more than 20% of the usual time in the heat on day 1, and no more than a 20% increase each day after. Workers with experience can ramp faster. Supervise new hires closely for the first 14 days. Workers returning from a long break or hit by early-season heat need a ramp too. See our acclimatization schedule guide and heat stress.