30 C.F.R. § 27.23 Automatic warning device.
Title 30 - Mineral Resources
(a) An automatic warning device shall be suitably constructed for incorporation in or with permissible and approved equipment that is operated in gassy mines and tunnels. (b) An automatic warning device shall include an alarm signal (audible or colored light), which shall be made to function automatically at a methane content of the mine atmosphere between 1.0 to 1.5 volume percent and at all higher concentrations of methane. (c) It is recommended that the automatic warning device be supplemented by a meter calibrated in volume percent of methane.
Title 30: Mineral Resources
PART 27—METHANE-MONITORING SYSTEMS
Subpart B—Construction and Design Requirements
§ 27.23 Automatic warning device.
