Foremen, superintendents, and site safety leads running outdoor construction crews — concrete, roofing, framing, excavation, road work — where the crew is in direct sun, in heavy PPE, or both, and the schedule for the next four to eight hours is yours to set.
Construction is the sector where heat rules bite hardest: the work is heavy (the metabolic-rate column that drives every schedule engine), it is outdoors under solar load (which is why the outdoor WBGT formula carries a globe-temperature term at all), and crews rotate on and off sites faster than acclimatization builds — the single factor that moves most published thresholds by 2–3°C.
Which heat rule applies to this crew, today? On a US jobsite the answer is layered, and the layers are not interchangeable:
The calculator resolves the layers for you: it evaluates every rule that could apply, then reports the single most protective applicable result. It never averages two standards together.
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.
These apply, or are cited, on any US jobsite regardless of state.
| Rule | Authority | Legal status | What it sets |
|---|---|---|---|
| OSHA Heat National Emphasis Program (CPL 03-00-024, April 2026) | US OSHA, Directorate of Enforcement Programs | Guidance — voluntary | Alert levels |
| OSHA Federal Heat Rule NPRM (Proposed) | US OSHA | Proposed rule — not yet enforceable | Control measures |
| CPWR / OSHA-CPWR Construction Heat Overlay | CPWR / OSHA-CPWR Alliance | Industry guidance — voluntary | Control measures |
| NIOSH 2016-106 Table 6-2 | NIOSH | Guidance — voluntary | Work/rest limits |
| NIOSH REL/RAL Logarithmic Curve | NIOSH | Guidance — voluntary | Screening thresholds |
| ACGIH TLV / Action Limit | ACGIH | Technical standard — not law unless adopted or incorporated | Work/rest limits |
Each of these binds only inside its own jurisdiction. Declare the worksite state in the calculator and the composite narrows to the rules that actually govern it.
| Rule | Authority | Legal status | What it sets |
|---|---|---|---|
| Cal/OSHA Outdoor Heat Illness Prevention (Title 8 §3395) | California Division of Occupational Safety and Health | Mandatory regulation | Control measures |
| Cal/OSHA Indoor Heat Illness Prevention (Title 8 §3396) | California Division of Occupational Safety and Health | Mandatory regulation | Control measures |
| Oregon OSHA Heat Illness Prevention Standard (AO 3-2022) | Oregon Occupational Safety and Health Division (Oregon OSHA) | Mandatory regulation | Work/rest limits |
| Washington State DOSH Outdoor Heat Standard (WAC 296-62-095) | Washington State Department of Labor & Industries (L&I/DOSH) | Mandatory regulation | Work/rest limits |
| Maryland OSHA Heat Stress Standard (COMAR 09.12.32) | Maryland Occupational Safety and Health (MOSH) | Mandatory regulation | Work/rest limits |
| Nevada OSHA Heat Illness Prevention Regulation (R131-24) | Nevada OSHA / Nevada Division of Industrial Relations | Mandatory regulation | Control measures |
| Minnesota OSHA Indoor Ventilation and Temperature Rule (5205.0110) | Minnesota OSHA | Mandatory regulation | Work/rest limits |
| NYC Executive Order No. 17 — Outdoor Worker Heat Protection | Office of the Mayor of New York City | Mandatory regulation | Control measures |
| San Antonio Contractor Outdoor Heat Ordinance | City of San Antonio | Mandatory regulation | Control measures |
Rules whose own text scopes them to construction or building work. Every other national rule still applies to construction as it does to any other sector — see the international page and the country index.
| Rule | Authority | Legal status | What it sets |
|---|---|---|---|
| Malta OHSA Construction Heat-Stress Instrument (Admin Instrument No. 2 of 2025) | Occupational Health and Safety Authority (OHSA), Malta | Mandatory regulation | Work/rest limits |
| Austria "Hitzefrei" Construction Rule (BSchEG) | BUAK / Austrian Federal Government | Mandatory regulation | Stop-work / banned hours |
| Tamil Nadu Heat Wave Action Plan (TNSDMA) + BOCW Outdoor-Work Timing Restriction | Tamil Nadu State Disaster Management Authority / Tamil Nadu Labour Department (BOCW) | Mandatory regulation | Stop-work / banned hours |
| Qatar Ministerial Decision No. 17 of 2021 | Qatar Ministry of Labour | Mandatory regulation | Stop-work / banned hours |
| UAE Midday Break Rule | UAE Ministry of Human Resources | Mandatory regulation | Stop-work / banned hours |
A rebar crew is placing steel in open sun. The site WBGT reads 31°C, the work is heavy, the crew has been on this site three weeks and is acclimatized, and the worksite is in the United States — but no state has been declared. That last part matters: a rule only binds where it governs, so with no state named only the jurisdiction-neutral and nationwide layers can set the schedule. Declare a state and the answer can only get stricter.
Inputs: WBGT 31°C · heavy work (415 W) · acclimatized worker · worksite country US, no state/province declared
| Rule | What it returns at these inputs |
|---|---|
| La Isla Network-informed RSH-s Default Protocol | 30 / 30 min work/rest per hr |
| ACGIH TLV / Action Limit | 15 / 45 min work/rest per hr |
| NIOSH REL/RAL Logarithmic Curve | 26.6°C limit — exceeded |
| CPWR / OSHA-CPWR Construction Heat Overlay | Moderate |
| OSHA Federal Heat Rule NPRM (Proposed) | 52 / 8 min work/rest per hr |
Answer for this shift: 15 / 45 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.