46 CFR §116.820

1. (a)A seat must be provided for each passenger permitted in a space for which the fixed seating criterion in § 115.113(b)(3) of this subchapter has been used to determine the number of passengers permitted.
2. (b)A seat must be constructed to minimize the possibility of injury and avoid trapping occupants.
3. (c)Installation of seats must provide for ready escape.
4. (d)Seats, including fixed, temporary, or portable seats, must be arranged as follows:
   1. (1)An aisle of not more than 3.8 meters (15 feet) in overall length must be not less than 610 millimeters (24 inches) in width.
   2. (2)An aisle of more than 3.8 meters (15 feet) in overall length must be not less than 760 millimeters (30 inches) in width.
   3. (3)Where seats are in rows, the distance from seat front to seat front must be not less than 760 millimeters (30 inches) and the seats must be secured to a deck or bulkhead.
   4. (4)Seats used to determined the number of passengers permitted, in accordance with § 115.113(b)(3) of this subchapter, must be secured to the deck, bulkhead, or bulwark.