Like many Cal/OSHA regulations, this is the first standard of its kind in the nation. It applies to workplaces where the Air Quality Index reaches 151 – unhealthy – and when employers “should reasonably anticipate” that employees may be exposed to wildfire smoke. Exempted are indoor workplaces and enclosed vehicles with filtered air, firefighters engaged in wildland firefighting, and employees with short-term exposure to the foul air (no more than one hour).