30 CFR § 27.1
The regulations in this part set forth the requirements for
methane-monitoring systems or components thereof to procure certification
for their incorporation in or with permissible equipment that is used in
gassy mines, tunnels, or other underground workings and procedures for
applying for such certification.
[31 FR 10607, Aug. 9, 1966, as amended at 52 FR 17515, May 8, 1987]