Supervisors, foremen, and safety staff running crews anywhere in California — outdoor agriculture and construction, and, since the indoor standard took effect, warehouses and production floors too.
California has the longest-running heat illness prevention standard in the United States, a companion indoor standard, and a wildfire-smoke standard that keys off AQI. In practice a Californian crew can be under all three at once on the same August afternoon.
Which heat rule applies to this crew, today? In California the state's own standards are the enforceable floor — they are what an inspector cites. Above them sit the federal enforcement posture and the technical standards that contracts and site safety plans commonly adopt.
Declare the worksite as California in the calculator and the composite narrows to exactly this set: a rule binds only where it governs, so California's rules bind here and another state's do not. Rules from elsewhere are still evaluated and shown, marked advisory.
California’s wildfire-smoke rule (§5141.1) is AQI-canonical: its dividers are written in AQI for PM2.5, not in µg/m³. Voluntary respirator use engages at AQI 151; a full written respiratory protection programme is required above AQI 500. The calculator accepts either an AQI or a PM2.5 concentration and converts using the EPA 2024 breakpoints.
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.
Derived from the registry: every standard declaring US-CA. Wildfire smoke, where the state has a rule, is listed separately below — it is a different hazard axis and never enters the work/rest composite.
| 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 |
| Cal/OSHA Outdoor Heat Illness Prevention (Title 8 §3395) | California Division of Occupational Safety and Health | Mandatory regulation | Control measures |
These apply, or are cited, in California as anywhere else in the US. Full national picture: United States country page.
| 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 |
| 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 |
| La Isla Network-informed RSH-s Default Protocol | La Isla Network / Adelante Initiative | Industry guidance — voluntary | Work/rest limits |
Wildfire smoke is a separate hazard axis from heat. It is tracked as its own smoke_overlay rule type and is never folded into the work/rest composite above — full respirator thresholds, including the EPA 2024 PM2.5 breakpoints, are on the wildfire smoke guidance page.
| Rule | Authority | Legal status | What it sets |
|---|---|---|---|
| Cal/OSHA Protection from Wildfire Smoke (Title 8 §5141.1) | California Division of Occupational Safety and Health | Mandatory regulation | Wildfire smoke thresholds |
A framing crew in the Central Valley in August: 37°C air, 30% relative humidity, a measured site WBGT of 31°C, heavy work, an acclimatized crew, and the worksite declared as California in the construction industry. §3395 reads plain air temperature and returns controls rather than minutes, so it does not set the schedule here — the schedule-producing standards do, and §3395’s shade, water, cool-down and high-heat duties apply on top of whatever schedule you run.
Inputs: air temperature 37°C · 30% relative humidity · WBGT 31°C · heavy work (415 W) · acclimatized worker · industry: construction · worksite declared in US-CA
| Rule | What it returns at these inputs |
|---|---|
| Cal/OSHA Outdoor Heat Illness Prevention (Title 8 §3395) | High-heat procedures (≥95°F) — construction |
| 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 |
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.