Preshift Exam Taken from the 2019 Virginia Mining Institute Preshift Contest held in Blacksburg, VA
Progress Indicator:
Question 1 of 10
1. Methane detectors should be calibrated with a known _____________ mixture at least once every 31 days. (30 CFR 75.320 (a))
Choices:
- Methane
- Methane-oxygen
- Methane-air
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