Involved with air sampling regulatory or compliance measurements to OSHA, NIOSH, ASTM, ARCA, CAR 2012 or HSG 248 standards then you should be gaining UKAS accredited calibrations for your master air flow sampling system. Regular UKAS accredited calibration of your air sampler system whether this be a flowmeter, flow calibrator or pump will ensure your sampling system remains compliant and accurate. All air sampler flow calibrations whether this be your working flowmeters or master flowmeters should have a complete line of traceability from a UKAS accredited calibration laboratory with a flow measurement uncertainty analysis to include in your overall measurement uncertainty budget. During calibration the air sampler flow rate is checked to ensure the volume flow rate of air is consistent with the instrument specification and upon completions a detailed certificate of calibration is issued inline with ISO/IEC 17025.
Air Sampling Methods and Calibration Procedures
Air sampling in practice draws a known volume of air through a sampling medium using a sampling pump and meter and is vital to any environmental monitoring program. For sampling of particulates, fumes, dust, trace metals and pollen the medium is generally a filter paper, as these contaminants are of solid material in the around µm to mm range, as anything larger would be too heavy to remain on the air and would fall to the ground. Sampling flow rates range from 50 ml/min up to 40 l/sec for high volume sampling. Sampling for gases, solvents and vapours instead of using a filter papers, or sometimes in addition would use a sorbent tube or impinger method, where sampling flow rate are much lower in the order of 10 – 100 ml/min. Calibration procedures, methods and sampling flow rates are specified in each standard such as NIOSH, EPA, HSG 248, OSHA, AHERA, ISO 13137 and MDHS, along with the calibration intervals for working flowmeters and master flowmeters. Personal sampling pumps must adhere to ISO 13137:2013 and are generally battery operated and bodily worn with the sampling inlet positioned in a manner which reflects the users' airborne environment and they must also comply to the standard specification for flow stability and pulsation limits. Flow calibration of the sampling pump system is completed before and after every sample run to calculate the average sample volume. This system calibration is generally completed by the user with a suitable UKAS accredited calibrated reference flowmeter.
