30 CFR §75.1714-7

1. (a)Availability. A mine operator shall provide an MSHA-approved, handheld, multi-gas detector that can measure methane, oxygen, and carbon monoxide to each group of underground miners and to each person who works alone, such as pumpers, examiners, and outby miners.
2. (b)Qualified person. At least one person in each group of underground miners shall be a qualified person under § 75.150 of this part and each person who works alone shall be trained to use the multi-gas detector.
3. (c)Maintenance and calibration. Multi-gas detectors shall be maintained and calibrated as specified in § 75.320 of this part.