N.Y.C. Admin. Code § MC 501: Section MC 501: General

501.1 Scope.

This chapter shall govern the design, construction and installation of mechanical exhaust systems, including exhaust systems serving clothes dryers and cooking appliances; hazardous exhaust systems; dust, stock and refuse conveyor systems; subslab soil exhaust systems; smoke control systems; energy recovery ventilation systems; and other systems specified in Section 502.

501.2 Independent system required.

Single or combined mechanical exhaust systems for environmental air shall be independent of all other exhaust systems except as permitted in Section 514. Dryer exhaust shall be independent of all other systems. Type I exhaust systems shall be independent of all other exhaust systems except as provided in Section 506.3.5. Single or combined Type II exhaust systems for food-processing operations shall be independent of all other exhaust systems. Kitchen exhaust systems shall be constructed in accordance with Section 505 for domestic equipment and Sections 506 through 509 for commercial equipment.

501.3 Exhaust discharge.

The air removed by every mechanical exhaust system shall be discharged outdoors at a point where it will not cause a nuisance and the air shaft will be located not less than the distances specified in Section 501.3.1. The air shall be discharged to a location from which it cannot again be readily drawn in by a ventilating system. Air shall not be exhausted into an attic or crawl space.

Exceptions:

1. Whole-house ventilation-type attic fans shall be permitted to discharge into the attic space of dwelling units having private attics.

2. Commercial cooking recirculating systems.

3. Where installed in accordance with the manufacturer's instructions and where mechanical or natural ventilation is otherwise provided in accordance with Chapter 4, listed and labeled domestic ductless range hoods shall not be required to discharge to the outdoors.

501.3.1 Location of exhaust outlets.

The termination point of exhaust outlets and ducts discharging to the outdoors shall be located with the minimum distances of separation specified in Items 1 through 6 of this section. Separation shall not be required between an air intake and the discharge air from non-evaporative heat rejection or heat absorption appliances such as air-cooled condensers, dry coolers, or heat pump evaporators; such air is not exhaust. The inlet and discharge of the appliance shall not reduce the effective separation of other exhausts from ventilation intakes to less than the required minimums.

1. For ducts conveying noxious, toxic, explosive or flammable vapors, fumes or dusts (including but not limited to exhaust from dry cleaning establishments and spray booths): 30 feet (9144 mm) from property lines; 10 feet (3048 mm) from operable openings into buildings; 6 feet (1828.8 mm) from exterior walls and roofs; 30 feet (9144 mm) from combustible walls and operable openings into buildings which are in the direction of the exhaust discharge; 10 feet (3048 mm) above adjoining grade. Additional requirements may apply to Hazardous Exhaust Systems; see Section 510.

2. For other product-conveying outlets: 10 feet (3048 mm) from the property lines; 3 feet (914.4 mm) from exterior walls and roofs; 10 feet (3048 mm) from operable openings into buildings; 10 feet (3048 mm) above adjoining grade; 10 feet from any exterior fire escape, stair, or balcony.

3. For all environmental air exhaust outlets: 3 feet (914.4 mm) from property lines separating lots; 3 feet (914.4 mm) from operable openings into buildings for all occupancies other than Group U, and 10 feet (3048 mm) from mechanical air intakes. Such exhaust outlets shall not be considered hazardous or noxious.

Exception: A 10 foot (3048 mm) separation is not required between a mechanical air intake and an exhaust outlet which serve either of the following:

1. a single room, dwelling or sleeping unit with less than 750 cfm (354 L/s) Class 1 exhaust air; or

2. a single dwelling or sleeping unit with less than 400 cfm (189 L/s) Class 2 exhaust air.

For this exception, the sum of any energy recovery device cross contamination and any re-entrainment of exhaust through the intake shall be less than 10% of the intake air flow as established by the manufacturer. The distance requirements from property lines and operable openings shall be maintained. Air Class shall be determined in accordance with ASHRAE Standard 62.1.

4. Exhaust outlets and openings serving structures in flood hazard areas shall comply with the additional requirements of Appendix G of the New York City Building Code.

5. For specific systems see the following sections:

5.1. Clothes dryer exhaust, Section 504.4.

5.2. Kitchen hoods and other kitchen exhaust equipment, Sections 506.3.13, 506.4 and 506.5.

5.3. Dust stock and refuse conveying systems, Section 511.

5.4. Subslab soil exhaust systems, Section 512.4.

5.5. Smoke control systems, Section 909.10.3 of the New York City Building Code.

5.6. Refrigerant discharge, Section 1105.7.

5.7. Machinery room discharge, Section 1105.6.1.

6. In Occupancy Groups R-2 and R-3 each dwelling unit may be individually exhausted directly to the outdoors with a dedicated exhaust fan and shall comply with the following:

6.1. The exhaust system for the kitchen and the toilet/baths may be combined to the inlet of a single fan, provided such exhaust system serves only one dwelling unit.

6.2. The dedicated exhaust from each dwelling unit shall be directed away from any window serving the same dwelling unit from which the exhaust is taken, and in addition, such exhaust opening shall terminate at least:

6.2.1. Two feet (609.6 mm) from any operational window or door serving the same dwelling unit.

6.2.2. Three feet (914.4 mm) from any operational window or door serving an adjoining dwelling unit.

6.2.3. Three feet (914.4 mm) from any operational window or door serving another occupancy group in the same building.

6.2.4. Ten feet (3048 mm) from any outdoor air intake opening other than intakes serving the same dwelling unit.

6.2.5. Ten feet (3048 mm) above the public sidewalk adjoining the same building.

6.2.6 All other minimum distances prescribed in items 1 through 5 of Section 501.3.1 shall be satisfied

501.3.1.1 Exhaust discharge.

Exhaust air shall not be directed onto walkways.

501.3.2 Exhaust opening protection.

Exhaust openings that terminate outdoors shall be protected with corrosion-resistant screens, louvers or grilles. Openings in screens, louvers and grilles shall be sized not less than 1/4 inch (6.4 mm) and not larger than 1/2 inch (12.7 mm). Openings shall be protected against local weather conditions. Louvers that protect exhaust openings shall comply with AMCA Standard 550. Outdoor openings located in exterior walls shall meet the provisions for exterior wall opening protective in accordance with the New York City Building Code.

501.3.2.1 Wind-driven rain.

All exterior louvers for building exhaust systems shall conform to the requirements of Chapter 16 of the New York City Building Code, where applicable, and the following:

1. Comply with the requirements of AMCA Standard 550. Louvers shall comply with the intrusion requirements of wind-driven rain without the use of a damper. Exhaust openings located in exterior walls shall meet the provisions for exterior wall opening protectives in accordance with Chapter 16 of the New York City Building Code; or

2. Be installed on a plenum configured to intercept any wind-driven rain penetrating the louver and to prevent the rain from entering the building ductwork system. Such plenum shall be waterproofed and equipped with a drainage system to convey water penetrating the louver directly to the outdoors or in accordance with the New York City Plumbing Code.

501.4 Pressure equalization.

Mechanical exhaust systems shall be sized to remove the quantity of air required by this chapter to be exhausted. The system shall operate when air is required to be exhausted. Where mechanical exhaust is required in a room or space in other than occupancies in R-3, such space shall be maintained with a neutral or negative pressure. If a greater quantity of air is supplied by a mechanical ventilating supply system than is removed by a mechanical exhaust for a room, adequate means shall be provided for the natural or mechanical exhaust of the excess air supplied. If only a mechanical exhaust system is installed for a room or if a greater quantity of air is removed by a mechanical exhaust system than is supplied by a mechanical ventilating supply system for a room, adequate makeup air consisting of supply air, transfer air or outdoor air shall be provided to satisfy the deficiency. The calculated building infiltration rate and openable area shall not be used to satisfy the requirements of this section.

501.5 Ducts.

Where exhaust duct construction is not specified in this chapter, such construction shall comply with Chapter 6.

501.6 Independent system required.

The following shall be independent of other exhaust systems:

1. Single or combined mechanical exhaust systems from bath, toilet, urinal, locker, service sink closets and similar rooms shall be independent of all other exhaust systems, except as permitted in Section 501.3.1.

2. A separate grease duct system shall be provided for each Type I hood except as provided in Section 506.3.5.

3. Hazardous exhaust systems shall be independent of other types of exhaust systems as provided in Section 510.