At what average rate should air be drawn through a personal monitoring pump?

The correct answer is that air should be drawn through a personal monitoring pump at an average rate of 2.25 liters per minute. This rate is standard in the field of occupational health for personal air monitoring, particularly where asbestos exposure is a concern.

The 2.25 liters per minute is considered optimal because it strikes a balance between adequately sampling the air for contaminants and ensuring the representative capture of airborne particulates or fibers over the monitoring period. This flow rate is also high enough to ensure that changes in exposure levels can be adequately detected while minimizing the risk of capturing too little air, which could lead to false readings or insufficient data for risk assessment.

Other flow rates like 1.0 liters per minute may not provide enough sample volume for accurate readings, while higher rates such as 3.0 or 4.0 liters per minute could lead to the possibility of altering the composition of the air sample, thereby skewing the results. Hence, the choice of 2.25 liters per minute is well-supported by regulatory guidelines and practical monitoring needs in the context of asbestos exposure.