---
title: "What Is Acclimatization? Heat Stress and Hydration Glossary"
description: "Acclimatization is the body's gradual adaptation to heat, such as sweating more efficiently. NIOSH says to build work time in the heat over 7 to 14 days."
url: https://jmarsolutions.multisites.ai/glossary/acclimatization
publisher: JMAR Solutions
phone: +1-214-632-7780
quote: https://jmarsolutions.multisites.ai/contact
---

Heat illness prevention

# Acclimatization

Acclimatization is the body's gradual adaptation to heat, such as sweating more efficiently. NIOSH says to build work time in the heat over 7 to 14 days.

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](https://jmarsolutions.multisites.ai/guides/heat-acclimatization-schedule) and [heat stress](https://jmarsolutions.multisites.ai/glossary/heat-stress).

[From JMAR SolutionsHydration programs and toolbox talks for crews](https://jmarsolutions.multisites.ai/hydration-programs)

## Related terms

-   [Heat stress](https://jmarsolutions.multisites.ai/glossary/heat-stress)
-   [Work/rest schedule](https://jmarsolutions.multisites.ai/glossary/work-rest-schedule)
-   [Heat illness prevention plan](https://jmarsolutions.multisites.ai/glossary/heat-illness-prevention-plan)
-   [HeatRisk](https://jmarsolutions.multisites.ai/glossary/heatrisk)

## Sources

1.  [CDC NIOSH: Workplace Recommendations](https://www.cdc.gov/niosh/heat-stress/recommendations/index.html)
2.  [CDC NIOSH: Workplace Recommendations](https://www.cdc.gov/niosh/heat-stress/recommendations/index.html)

![Ironworkers silhouetted on a steel frame against a hot orange sunset](https://jmarsolutions.multisites.ai/_astro/sunset-steel.IhAMDca0_6wk53.webp)

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