Section 304 defines Group B occupancies as buildings or portions thereof for office, professional, or service transactions, including medical offices, banks, post offices, and insurance companies. This broad category includes administrative functions, general office space, and professional practices that do not involve hazardous processes or large quantities of hazardous materials. Group B occupancies typically have lower life safety requirements compared to assembly or institutional uses because occupants are relatively familiar with the building and egress routes. The occupant load for general office areas is calculated at one person per 150 square feet of floor area, allowing for efficient facility design. Egress requirements specify minimum exits based on floor area and occupant load, with specific travel distance limitations typically not exceeding 200 feet to an exit in sprinklered buildings or 150 feet in non-sprinklered buildings. Automatic sprinklers are required in buildings exceeding specific height and area thresholds or when interior finishes include higher flame-spread ratings. Medical offices housing operating facilities must meet enhanced fire safety requirements including operating room sprinklers and specific alarm systems. Banks and financial institutions must include security vestibules and specific design features. Professional service areas are generally treated as standard office space with standard code requirements unless they contain laboratories or other specialized functions.