Abstract: An extensible brattice and cantilevered support system therefor comprises a brattice panel having first and second top sleeves and a weighted bottom sleeve suspended from selected roof bolts by a support system comprising a support to which the brattice panel is mounted and which defines a track, and mounting apparatus for each roof bolt comprising a coupler connected to the panel support in sliding engagement with the support track, an elongate member connected to the coupler, an upstanding, roof abutting leg member connected to the elongate member at a location longitudinally spaced from the coupler, and a member connecting the elongate member in depending relation to the associated roof bolt at a position on the elongate member intermediate the coupler and leg member.

Abstract: The effectivenss of a seal for extinguishing fires in an underground mine passage is determined by transmitting acoustic energy from a first site toward the seal. The acoustic energy is detected at a second site on the opposite side of the seal from the transmitting site. To provide for remote monitoring of the seal, acoustic transmitter and receiver means are lowered into the passage to the first and second sites through vertical bores. The effectiveness of the seal is determined by the amplitude of the detected acoustic energy. The size of any hole in the seal is determined by comparing the amplitude of the detected energy after the seal has been started and prior to the sealing operation commencing. The acoustic energy has a carrier frequency that randomly varies over a relatively broad band to prevent acoustic nodes in the passageway.