505.1 Domestic Systems Where domestic range hoods or domestic appliances equipped with downdraft exhaust are provided, such hoods and appliances shall discharge to the outdoors through ducts constructed of galvanized steel, stainless steel, aluminum or copper. Such ducts shall have smooth inner walls, shall be air tight, shall be equipped with a backdraft damper and shall be independent of all other exhaust systems. Such exhaust system shall be installed in strict compliance with the manufacturer's instructions as well as the requirements of the listing. Exceptions:
In other than Group I-1 and I-2, 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 ductless range hoods shall not be required to discharge to the outdoors.
Ducts for domestic kitchen cooking appliances equipped with downdraft exhaust systems shall be permitted to be constructed of Schedule 40 PVC pipe and fittings provided that the installation complies with all of the following:
The duct shall be installed under a concrete slab poured on grade.
The underfloor trench in which the duct is installed shall be completely backfilled with sand or gravel.
The PVC duct shall extend not more than 1 inch (25.4 mm) above the indoor concrete floor surface.
The PVC duct shall extend not more than 1 inch (25.4 mm) above grade outside of the building.
The PVC ducts shall be solvent cemented.
505.2 Makeup Air Required Exhaust hood systems where required by Chapter 4 shall be provided with makeup air at a rate in accordance with Table 403.3.1.1. Such makeup air systems shall be equipped with a means of closure and shall be automatically controlled to start and operate simultaneously with the exhaust system.
From Table 403.3.1.1
Kitchens and Kitchenettes
EXHAUST AIRFLOW RATE CFM/FT2
25/100f
f. Rates are per room unless otherwise indicated. The higher rate shall be provided where the exhaust system is designed to operate intermittently. The lower rate shall be permitted only where the exhaust system is designed to operate continuously while the dwelling unit or sleeping unit served by the toilet facility is occupied.
b. Mechanical exhaust required and the recirculation of air from such spaces is prohibited (see Section 403.2.1, Item 3).
m. Exception: kitchens and kitchenettes in dwelling units of R-2 occupancy may be naturally ventilated in accordance with Section 402.
Comments