کالیبراسیون پمپ نمونهبرداری هوای فردی
(Personal Air Sampling Pump Calibration)
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I'm going to go over how to calibrate a personal air sampling pump with an electronic calibrator which is a primary standard. Air sampling pumps need to be calibrated directly before and after each sample in order to accurately calculate the volume of air that's been sampled.
You should also calibrate your pumps at a temperature and elevation or pressure that's as similar as possible to your sampling location. First we want to ensure that our pump is fully charged and we need to have it running for at least five minutes before performing the calibration.
During this time we'll prepare our media or our sampling cassettes and inspect our tubing for cracks and leaks. Also inspect your pump to verify that it appears to be working and isn't on its last leg, make sure that it doesn't look like it's been recently dropped.
To perform the calibration we'll use the same media type and sampling train which is just our sampling setup that will be used during our sample collection but we won't use the exact same cassette. Using the same cassette to calibrate that will be used for sampling may introduce contaminants into your sample so it's important to have designated media to perform your calibration.
Once your pump is sufficiently warmed up align your sampling train so that your pump is sucking from the suction port of your electronic calibrator. Ensure that the pressure port is clear if the pump seems unusually loud there may be a blockage in your sampling train that's preventing air flow so address that immediately.
Use the screwdriver to adjust the flow rate to the level required based on your sampling time required sample volume and approved analytical procedure. In this case we're using NIOSH method zero 504 total dust while this flow rate will vary depending on the procedure there are very specific flow rates for particle size selectors such as cyclones so always verify that you're operating within the approved range for the procedure.
Once you've adjusted the pump to your desired flow rate perform at least three consecutive measurements that should be within two percent of each other average these measurements and turn off your pump before sampling be sure to attach fresh media to your pump.
After your sampling is complete and before charging your pump repeat the calibration procedure without any pump adjustments take at least three consecutive samples and verify that your post sampling calibration is within plus or minus 5% of your pre sampling calibration value.
If your flow rate is not within plus or minus 5% of your pre sampling calibration value then you must discard your sample happy sampling.
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