Shift leads and EHS staff in warehouses, distribution centres, fulfilment operations, and production floors — anywhere the work is indoors, unconditioned or partly conditioned, and the roof load, equipment heat, and pick rate combine into a real thermal exposure that no outdoor forecast will show you.
Which heat rule applies to this crew, today? Indoor work sits under a different set of rules from outdoor work, and confusing the two is the common failure:
WBGT = 0.7·Tnwb + 0.3·Tg, not the outdoor 0.7/0.2/0.1 weighting. Feeding an outdoor value into an indoor rule, or the reverse, produces a wrong number, not a conservative one.Legal status below is the registry's own legalStatus field for each rule. A "mandatory regulation" is enforceable law in its jurisdiction; everything else is guidance, a technical standard, or a proposal, and binds you only if your contract, your client, or your own programme adopts it.
Rules whose own text is scoped to indoor workplaces.
| Rule | Authority | Legal status | What it sets |
|---|---|---|---|
| Cal/OSHA Indoor Heat Illness Prevention (Title 8 §3396) | California Division of Occupational Safety and Health | Mandatory regulation | Control measures |
| Minnesota OSHA Indoor Ventilation and Temperature Rule (5205.0110) | Minnesota OSHA | Mandatory regulation | Work/rest limits |
| Germany ASR A3.5 Room Temperature Rule | BAuA / Germany Federal Ministry of Labour and Social Affairs | Technical standard — not law unless adopted or incorporated | Control measures |
| Latvia Cabinet Regulation No. 359 — Workplace Microclimate Limits | Cabinet of Ministers, Republic of Latvia (enforced by State Labour Inspectorate, VDI) | Mandatory regulation | Control measures |
| Lithuania HN 69:2003 Indoor Temperature Ceilings + VDI Outdoor Heat-Break Guidance | Lietuvos Respublikos sveikatos apsaugos ministerija (Ministry of Health, HN 69:2003) / Valstybine darbo inspekcija (VDI -- State Labour Inspectorate, outdoor break guidance) | Mandatory regulation | Control measures |
| Denmark Arbejdstilsynet Indoor-Climate Temperature Guidance | Arbejdstilsynet (Danish Working Environment Authority) | Guidance — voluntary | Control measures |
| Norway Arbeidstilsynet Workplace Temperature Guidance | Arbeidstilsynet (Norwegian Labour Inspection Authority) | Guidance — voluntary | Control measures |
| Finland Työsuojelu Kuumatyö (Hot Work) Indoor Break Schedule | Työsuojeluhallinto (Finnish Occupational Safety and Health Administration), guidance developed jointly with Työterveyslaitos (Finnish Institute of Occupational Health, FIOH) | Guidance — voluntary | Work/rest limits |
These take an indoor WBGT (or, for ISO 7933, the full environmental parameter set) and are not scoped to a setting.
| Rule | Authority | Legal status | What it sets |
|---|---|---|---|
| ACGIH TLV / Action Limit | ACGIH | Technical standard — not law unless adopted or incorporated | Work/rest limits |
| NIOSH 2016-106 Table 6-2 | NIOSH | Guidance — voluntary | Work/rest limits |
| NIOSH REL/RAL Logarithmic Curve | NIOSH | Guidance — voluntary | Screening thresholds |
| ISO 7243:2017 WBGT Screening | ISO | Technical standard — not law unless adopted or incorporated | Screening thresholds |
| ISO 7933 Predicted Heat Strain (PHS) | ISO | Technical standard — not law unless adopted or incorporated | Work/rest limits |
Framework and general-duty rules with no numeric indoor ceiling of their own, but which still oblige an employer to assess and control indoor thermal risk.
| Rule | Authority | Legal status | What it sets |
|---|---|---|---|
| EU Framework Directive 89/391/EEC | European Union | Mandatory regulation | Control measures |
| UK HSE Temperature Guidance | UK Health and Safety Executive | Guidance — voluntary | Control measures |
| OSHA Federal Heat Rule NPRM (Proposed) | US OSHA | Proposed rule — not yet enforceable | Control measures |
A pick-and-pack floor in an uninsulated distribution centre reads an indoor WBGT of 28°C in the late afternoon. The work is moderate — walking, lifting cartons — and the crew is a mix of regulars and agency staff, so the unacclimatized case is the one to plan against. No country is declared, so only the jurisdiction-neutral technical thresholds can bind.
Inputs: WBGT 28°C · moderate work (300 W) · unacclimatized worker · no worksite country declared
| Rule | What it returns at these inputs |
|---|---|
| ACGIH TLV / Action Limit | 30 / 30 min work/rest per hr |
| NIOSH REL/RAL Logarithmic Curve | 25°C limit — exceeded |
| ISO 7243:2017 WBGT Screening | 26°C limit — exceeded |
Answer for this shift: 30 / 30 min work/rest per hr (most protective)
Every value above is computed at build time by the same engine the live calculator runs — the single most protective applicable result, never an average across standards. Change any input and the answer changes, which is what the calculator is for.
Screening-level guidance. This tool provides screening-level heat guidance for planning. It is a decision-support instrument, not a sole compliance authority or a medical prescription. Verify against the governing standard for your jurisdiction and consult a qualified professional for individual medical decisions.