14 CFR 252.7 - No-smoking sections.
(a) Except as provided in paragraph (b) of this section, air carriers operating nonstop flight segments to which §§ 252.3 and 252.13 do not apply shall provide, at a minimum:
(1) A no-smoking section for each class of service;
(2) A sufficient number of seats in each no-smoking section to accommodate all persons in that class of service who wish to be seated there;
(3) Expansion of no-smoking sections to meet passenger demand; and
(4) Special provisions to ensure that if a no-smoking section is placed between smoking sections, the nonsmoking passengers are not unreasonably burdened.
(b) On flights for which passengers may make confirmed reservations and on which seats are assigned before boarding, an air carrier need not provide a seat in a no-smoking section to a passenger who has not met the carrier's requirements as to time and method of obtaining a seat on the flight, or who does not have a confirmed reservation. If a seat is available in the established no-smoking section, however, an air carrier shall seat there any enplaning passenger who so requests, regardless of boarding time or reservation status.