In a coal mine containing neither highly explosive coal dust nor methane, the wire mesh of a Davy lamp must be very tightly spaced; while for flame arresters used as a safety device, it must be protected from damage due to being dropped or struck by another object.
In a coal mine containing neither highly explosive coal dust nor methane, the wire mesh of a Davy lamp must be very tightly spaced; while for flame arresters used as a safety device, it must be protected from damage due to being dropped or struck by another object.