All doors and openings along accessible routes shall comply with the following requirements.
Exceptions: Openings greater than 24 inches (24" = 6110mm) in depth are not doorways but may be part of an accessible route, in which case they shall comply with 521 CMR 20.00: ACCESSIBLE ROUTES and 521 CMR 24.00: RAMPS (SeeFig. 26a). Doors not requiring full user passage, such as shallow closets, may have the clear opening reduced to 20 inches (20" = 508mm) minimum, See521 CMR 9.5.8, Closets.
521 CMR, § 26.1