Section 303 defines Group A occupancies as buildings or portions thereof in which persons gather for civic, social, or religious functions, recreation, dining, or awaiting transportation. Assembly occupancies are further subdivided into A-1, A-2, A-3, A-4, and A-5 classifications. A-1 occupancies include theaters with fixed seating, concert halls, and auditoriums with capacities typically exceeding 250 persons, requiring sophisticated life safety systems. A-2 occupancies are nightclubs, bars, restaurants with bars, and banquet halls where alcohol is served. A-3 occupancies encompass general assembly spaces including museums, churches, lecture halls, and community centers with diverse public access. A-4 occupancies are arenas, skating rinks, and swimming pools with large mobile occupant loads. A-5 occupancies include outdoor structures such as amphitheaters, bleachers, grandstands, and open-air pavilions. Assembly occupancies require minimum two exits for occupant loads exceeding 50, with specific travel distance limitations and egress width calculations based on occupant load. Automatic sprinkler protection is typically mandated, and detailed emergency lighting and signage requirements apply. Occupant load calculations for assembly spaces are strictly prescribed, requiring one person per 4 square feet for theater seating and varying rates for other uses. Ancillary spaces within assembly occupancies must be addressed, including kitchens, dressing rooms, and projection booths.