The two numbers that run the job
OSHA sets two numbers for respirable crystalline silica. The action level is 25 micrograms per cubic meter of air, measured as an 8-hour time-weighted average. The permissible exposure limit, the PEL, is 50 micrograms per cubic meter over the same 8-hour shift. Both standards use the same numbers: the construction rule and the general industry rule. Frac sand is industrial sand, and OSHA lists hydraulic fracturing as a source of this dust. Exposure is averaged over the shift, so a burst of dust can put a crew over the limit for the day. When exposure may reach the action level, the employer must measure it, and re-check within six months if the reading sits between the action level and the PEL.
Water, vacuum, and wet methods come first
The standard does not start with respirators. It starts with engineering controls. Wet methods need enough water to keep visible dust out of the air. HEPA-filtered vacuuming is the approved cleanup, and dry sweeping is out where it would add to exposure. Enclosed cabs must hold positive pressure and filter the intake air. The employer must use engineering and work practice controls to hold exposure below the PEL. Respirators only step in when controls cannot do the job alone.
Respirators are backup. Paperwork is the proof.
Respirators are allowed when exposure stays above the PEL after controls, while controls are being installed, and for tasks where controls cannot work. Required respirator use must run through a full program with fit testing and training. The employer also has to document. A written exposure control plan must list tasks, controls, housekeeping, and respirator use, and it must be reviewed at least once a year. A competent person must inspect job sites and equipment regularly. Exposure records and medical records must be kept and made available. Anyone using a respirator 30 or more days a year gets medical surveillance at no cost.
Silica exposure does not show up in a report the way a near miss does, which is why the standard leans on records. Pair it with solid H2S monitoring at the wellsite, keep HazCom and SDS in the oilfield current, and run a job safety analysis in the field before the work starts. If your records do not prove the controls, start with an operations audit.