Smoke season in California is now a routine operating condition rather than an emergency, and 8 CCR section 5141.1 treats it that way. The trigger is specific: the current air quality index for PM2.5 is 151 or greater.
What the number means
An AQI of 151 is the bottom of the “unhealthy” band for fine particulate. It is not a forecast and it is not a daily average taken after the fact — it is the current reading for the location where people are working. That distinction decides how an employer has to monitor: someone has to check, during the shift, from a source that reports current conditions for that area, and record what was found.
Employers with crews spread across a county learn quickly that one reading does not cover them. Smoke settles into valleys and drainages and lifts unevenly through the day. A crew twelve miles from the office can be in a different band for hours.
Respirators are the last control, not the first
The order of preference is the same as for any airborne hazard. Relocate the work indoors where the air is filtered. Change the schedule. Reduce the exertion, because minute ventilation is what turns an ambient concentration into a dose. Then, when exposure cannot be avoided, provide filtering facepiece respirators.
Two practical points follow. First, a respirator handed out without training is a fitting hazard of its own; people wear them under a beard, over a ball cap strap, or pulled down to talk. Second, once the exposure exceeds the level at which use becomes mandatory rather than voluntary, the employer has stepped into a full respiratory protection program — medical evaluation, fit testing, written program — and that is a different obligation from handing out N95s in a smoky week.
Training people are willing to act on
Wildland crews learn early to judge smoke by what it does to breathing and visibility, not by how impressive the column looks. Ordinary outdoor workers have no such calibration and will work through conditions they should not, because the sky is orange every September and nothing obvious happens on the day. Training that connects the reading to the symptom — and gives a worker permission to say so — changes behaviour. A slide that says “monitor the AQI” does not.
Michael Karl McNeil — former Fire Battalion Chief; industrial hygiene and emergency planning.
Michael Karl McNeil 