407.4 Air Circulation.

407.4.1 Design of the ventilation system shall provide air movement that is generally from clean to less clean areas.

407.4.1.1 Air supplied to operating rooms, cesarean operating rooms, cardiac catheterization labs, cys- toscopy rooms, delivery rooms, and nurseries shall be delivered at or near the ceiling of the area served. In these areas and in morgues and autopsy rooms all air removed from the area shall be removed near floor level. Exhaust or recirculation inlets shall be located not less than 3 inches (76 mm) nor more than 8 inches (203 mm) above the finished floor, except in morgues and autopsy rooms where all of the exhaust air is removed through an autopsy table designed for this purpose. At least two exhaust or recirculation air inlets of equal capacity shall be used in all cardiac catheterization labs, cystoscopy rooms, operating rooms, and delivery rooms and shall be located not less than 3 inches (76 mm) nor more than 8 inches (203 mm) above the finished floor. Exception: For airborne infection isolation rooms and protective environment rooms, see Sections 414.0 and 415.0. 407.4.1.2 Room supply air outlets and room recir- culation and exhaust air inlets installed in nonsensi- tive areas shall be located not less than 3 inches (76 mm) above the floor. Exception: For airborne infection isolation rooms and protective environment rooms, see Sections 414.0 and 415.0. 407.4.1.3 Corridors shall not be used to convey sup- ply, return, transfer or exhaust air to or from any room if the corridor is required to be fire resistive construction per the California Building Code. Exceptions: (1) Mechanically exhausted toilet rooms of 50

square feet (4.7 m ² ) or less and small rooms of 30 square feet (2.79 m ² ) or less such as janitor closets, housekeeping rooms, and electrical or telephone closets opening directly onto corridor. (2) Air transfer caused by pressure differentials in

rooms required to have a positive or negative air balance by Table 4-A. 407.4.1.4 No space above a ceiling may be utilized as an outside-air, relief-air, supply-air, exhaust-air, or return-air plenum. Exception: Designs specifically approved by the enforcing agency. 407.4.1.5 Air from a patient room, exam room, treat- ment room shall not be transferred to another simi- lar room without first having passed through air filters as required by Table 4-B or Table 4-C.

2022 CALIFORNIA MECHANICAL CODE 69

VENTILATION AIR

407.4.1.6 Supply outlets and return and exhaust air inlets shall be located to prevent short-circuiting. 407.4.1.7 Recirculating Room Units. For spaces where Table 4-A permits air to be recirculated by room units, the portion of the minimum total air changes per hour required for a space that is greater than the minimum outdoor air changes per hour required component may be provided by recirculat- ing room HVAC units. Such recirculating room HVAC units shall: (1) not receive nonfiltered, nonconditioned outdoor

air; (2) serve only a single space; and (3) provide filtration per Section 408.2 and Section

408.3 for airflow passing over any surface that is designed to condense water. This filter shall be located upstream of any such cold surface, so that all of the air passing over the cold surface is fil- tered.