46 CFR §154.709

1. (a)The continuous gas detection system required under § 154.706(a)(2) and (b) must:
   1. (1)Meet § 154.1350(c), (d), and (j) through (s); and
   2. (2)Have a device that:
      1. (i)Activates an audible and visual alarm at the machinery control station and in the wheelhouse if the methane concentration reaches 1.5 percent by volume; and
      2. (ii)Closes the master gas fuel valve required under § 154.708(c) before the methane concentration reaches 3 percent by volume.
2. (b)The number and arrangement of gas sampling points must be specially approved by the Commandant (CG-OES).