CFR > Title 46 - Shipping > CHAPTER I—COAST GUARD, DEPARTMENT OF HOMELAND SECURITY > SUBCHAPTER O—CERTAIN BULK DANGEROUS CARGOES (parts 150 to 155) > PART 154—SAFETY STANDARDS FOR SELF-PROPELLED VESSELS CARRYING BULK LIQUEFIED GASES > SUBPART C—Design, Construction and Equipment (§154.170 to §154.1440) > 154.345—Air locks.

154.345—Air locks.

(a) An air lock may be used for access from a gas-dangerous zone on the weather deck to a gas-safe space.
(b) Each air lock must:
(1) Consist of two steel doors, at least 1.5 m (4.9 ft.) but not more than 2.5 m (8.2 ft.) apart, each gasketed and tight when tested with a fire hose at not less 207 kPa gauge (30 psig);
(2) Have self-closing doors with no latches or other devices for holding them open;
(3) Have an audible and visual alarm on both sides which are actuated when both door securing devices are in other than the fully closed position at the same time;
(4) Have mechanical ventilation in the space between the doors from a gas-safe area;
(5) Have a pressure greater than that of the gas-dangerous area on the weather deck;
(6) Have the rate of air change in the space between the doors of at least 8 changes per hour; and
(7) Have the space between the doors monitored for cargo vapor leaks under § 154.1350.
(c) In addition to the requirements of paragraphs (a) and (b) of this section, no gas-safe space on a liquefied flammable gas carrier may have an air lock unless the space:
(1) Is mechanically ventilated to make the pressure in the space greater than that in the air lock; and
(2) Has a means of automatically de-energizing all electrical equipment that is not explosion-proof in the space when the pressure in the space falls to or below the pressure in the air lock.