Field area of the graticule is determined by multiplying which two quantities?

• A. Time x Filter Area
• B. Flow Rate x Time
• C. Field Area x Sample Time
• D. Sample Count x Flow Rate

Answer: (B)

The main idea is that the field of air sampled by the graticule is determined by how much air actually moves through the sampler and for how long it runs. The total air volume, or the field of air examined, is obtained by multiplying the flow rate (how much air passes through per unit time) by the sampling time (how long you run the sampler). This gives you the total volume of air drawn through the system during the run, which is the quantity you use when calculating concentrations or deposits.

For example, if the sampler draws air at 2 liters per minute for 30 minutes, the total air volume processed is 60 liters. That volume represents the field of air encountered by the graticule during the sampling period.

The other options don’t give a direct measure of the air processed. Time multiplied by filter area yields an area-times-time unit that doesn’t correspond to how much air was drawn. Field area times sample time combines quantities in a way that doesn’t translate to air volume. Sample count multiplied by flow rate would require additional information and still wouldn’t directly equal the total air sampled.