403.1 Ventilation system.

Mechanical ventilation shall be provided by a method of supply air and return or exhaust air. The amount of supply air shall be approximately equal to the amount of return and exhaust air. The system shall not be prohibited from producing negative or positive pressure; such pressures shall not result in door opening forces in excess of those indicated in the New York City Building Code and shall not prevent doors from closing as required by the New York City Building Code. The method to convey ventilation air shall be designed and installed in accordance with Chapter 6.

403.2 Outdoor air required.

The minimum outdoor airflow rate shall be determined in accordance with Section 403.3.1.1.

   Exception: The minimum required rate of outdoor air may be reduced where the registered design professional demonstrates that an engineered ventilation system is designed in accordance with ASHRAE 62.1 Indoor Air Quality Procedure.

403.2.1 Recirculation of air.

The outdoor air required by Section 403.3.1.1 shall not be recirculated. Air in excess of that required by Section 403.3.1.1 shall not be prohibited from being recirculated as a component of supply air to building spaces, except that:

   1.   Ventilation air shall not be recirculated from one dwelling unit to another or to dissimilar occupancies.

   2.   Supply air to a swimming pool and associated deck areas shall not be recirculated unless such air is dehumidified to maintain the relative humidity of the area at 60 percent or less. Air from this area shall not be recirculated to other uses or occupancies.

   3.   Where mechanical exhaust is required by Note b in Table 403.3.1.1, recirculation of air from such spaces shall be prohibited. Recirculation of air that is contained completely within such spaces shall not be prohibited. Where recirculation of air is prohibited, all air supplied to such spaces shall be exhausted, including any air in excess of that required by Table 403.3.1.1.

   4.   Where mechanical exhaust is required by Note g in Table 403.3.1.1, mechanical exhaust is required and recirculation is prohibited. Recirculation of air that is contained completely within such spaces shall not be prohibited.

403.2.2 Transfer air.

Except where recirculation from such spaces is prohibited by Table 403.3.1.1, air transferred from occupiable spaces is not prohibited from serving as makeup air for required exhaust systems in such spaces as kitchens, baths, toilet rooms, elevators and smoking lounges. The amount of transfer air and exhaust air shall be sufficient to provide the flow rates as specified in Section 403.3.1.1. The required outdoor airflow rates specified in Table 403.3.1.1 shall be introduced directly into such spaces or into the occupied spaces from which air is transferred or a combination of both.

403.3 Outdoor air and local exhaust airflow rates.

Buildings that are not more than three stories in height above grade plane, and that (i) are within Occupancy Group R-2 or Occupancy Group R-3, (ii) are adult homes or enriched living housing as described in Section 308.3.1 of the New York City Building Code, within Occupancy Group I-1 and have 16 occupants or fewer, or (iii) are community residences or intermediate-care facilities as described in Section 308.3.2 of the New York City Building Code, shall be provided with outdoor air and local exhaust in accordance with Section 403.3.1.1.2. All other buildings intended to be occupied shall be provided with outdoor air and local exhaust in accordance with Sections 403.3.1.1 through 403.3.1.6.

403.3.1 Reserved.