46 CFR § 153.955 - Warning signs during cargo transfer.
(a) When transferring cargo while fast to a dock or at anchor in port, the master shall ensure that the tankship displays a warning sign at the gangway facing the shore so that it may be seen from the shore and another warning sign facing outboard toward the water so that it may be seen from the water. (See figure 1).
(b) Except as provided in paragraph (f) of this section, each warning sign must have the following legends:
(2) Dangerous Cargo.
(3) No Visitors.
(4) No Smoking.
(5) No Open Lights.
(c) Each letter must be block style, black on a white background.
(d) Each letter must:
(1) Be 7.5 cm (approx. 3 in.) high;
(2) Be 5 cm (approx. 2 in.) wide except for “M” and “W” which must be 7.5 cm (approx. 3 in.) wide and the letter “I” which may be 1.3 cm (approx. 1/2 in.) wide; and
(3) Have 1.3 cm (approx. 1/2 in.) stroke width.
(e) The spacing must be:
(1) 1.3 cm (approx. 1/2 in.) between letters of the same word;
(2) 5 cm (approx. 2 in.) between words;
(3) 5 cm (approx. 2 in.) between lines; and
(4) 5 cm (approx. 2 in.) at the borders of the sign.