46 CFR 35.30-1 - Warning signals and signs - TB/ALL.
(a)Red warning signals. During transfer of bulk cargo while fast to a dock, a red signal (flag by day and electric lantern at night) shall be so placed that it will be visible on all sides. While transferring bulk cargo at anchor, a red flag only shall be displayed.
(b)Warning sign at gangway. A sign shall be displayed to warn persons approaching the gangway, while a vessel is moored or anchored unless it is empty and gas-freed. The sign shall state in letters not less than 2 inches high substantially as follows:
No open lights.
(c)Warning sign in radio room. A sign shall be placed in radio room warning against the use of radio equipment during transfer of Grade A, B, or C liquids, except by permission of senior deck officer.
(e) Additional placards or signs required in connection with the movement of certain open hopper type barges are described in § 35.01-45.