Move heat controls upstream into the work plan.

Use the inputs a project engineer can influence before release: heat index, task intensity, shift duration, PPE burden, acclimatization, and radiant exposure. This is a planning screen for prioritizing controls upstream, not a WBGT measurement. For field compliance, use measured WBGT with the ACGIH or NIOSH work/rest tables.

Heat index iA screening proxy for air temperature and humidity (the public heat index). The occupational standard for field decisions is measured WBGT with the ACGIH/NIOSH work-rest tables. This planner prioritizes controls at the work-packaging stage; it does not replace WBGT monitoring or site safety rules.96 F Exposure duration 8 hr Crew size (monitoring span) iCrew size does not change an individual worker's heat strain, so it does not feed the exposure score. It sizes the observation load: more workers need more eyes to catch early symptoms.12

Task intensity iApproximate ACGIH metabolic categories. Light: light assembly, monitoring. Medium: sustained walking, moderate lifting, hand-tool work. Heavy: shoveling, manual material handling, sustained overhead work.

Radiant exposure

PPE burden iRequired PPE can add heat strain by trapping heat or limiting evaporation, even when the hazard control is necessary.

Acclimatization iNew, returning, or mixed crews need more conservative planning because heat tolerance builds over repeated exposure.

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65 pressure

Planning pressure

Controlled high exposure

The work can proceed only with planned recovery, shade access, and supervisor-visible exposure checks.

30 / 15 work/rest start point

Hourly field review

Resequence first lever

Control package

Exposure drivers

Foundations

This planning screen draws on established heat-stress practice:

ACGIH TLV — Heat Stress & Strain — WBGT-based occupational exposure limits and work/rest
NIOSH Criteria for Occupational Exposure to Heat — acclimatization, hydration, recovery
OSHA Heat NEP — National Emphasis Program on outdoor and indoor heat hazards
NWS Heat Index — caution-to-danger categories (basis for the 103°F floor)

Planning support only. This does not replace OSHA requirements, a heat illness prevention plan, medical judgment, or site-specific safety authority.