When does the OSHA reference method require calibration of air samples?

The correct response is that the OSHA reference method requires calibration of air samples both before and after sampling. This is essential to ensure the accuracy and reliability of the measurements obtained during the sampling process. Calibration before sampling establishes a baseline, ensuring the equipment is functioning correctly and providing valid results from the outset.

After sampling, calibration is equally important as it confirms that no drift in measurement has occurred during the sampling period. This post-sampling calibration helps to verify that the equipment maintained its accuracy throughout the entire sampling event. Together, these practices ensure that any data collected will be both accurate and reliable, which is crucial for compliance with safety standards and for protecting health in environments where asbestos is present.

Other approaches, such as calibrating just once before or just after collection, would not sufficiently address potential changes that could occur during sampling, thereby compromising the integrity of the data. The requirement for calibration both before and after underscores the importance of rigorous quality control in exposure assessments and monitoring activities.