Drager BG4 Statements of Fact 2 Questions taken from 2017 Drager BG4 Statements of Fact Progress Indicator: Question 5 of 15 5.  CPDMs must be checked by a certified person in sampling using the CPDM or in maintenance and calibration for the CPDM within _______ hours before the start of the shift on which the device will be used to collect respirable dust samples. Choices: 2 3 4 5