When testing for crystalline silica, you may use either a performance option or scheduled monitoring. You can do both methods, if needed, as long as you accurately test and keep records of the results.
If you choose performance testing, you test the air where a worker performs their duties to accurately reflect the amount of exposure they have during an eight-hour day.
The scheduled monitoring takes air samples in breathing zones that reflect worker exposures at various times, in different job capacities and across multiple work areas. It also involves follow-up samples at specified intervals based on whether the initial readings showed levels above the minimum threshold of 25 µg/m3.
For either method of testing, you must repeat the procedure if workplace methods such as engineering controls, personnel, processes or production changes.