The maximum allowable exhaust duct length shall be determined by one of the methods specified in Section M1502.4.4.1 or M1502.4.4.2.M1502.4.4.1 Specified length.
The maximum length of the exhaust duct shall be 35 feet (10 668 mm) from the connection to the transition duct from the dryer to the outlet terminal. Where fittings are used, the maximum length of the exhaust duct shall be reduced in accordance with Table M1502.4.4.1. The maximum length of the exhaust duct does not include the transition duct.
DRYER EXHAUST DUCT FITTING EQUIVALENT LENGTH
|DRYER EXHAUST DUCT FITTING TYPE||EQUIVALENT LENGTH|
|4 inch radius mitered 45 degree elbow||2 feet 6 inches|
|4 inch radius mitered 90 degree elbow||5 feet|
|6 inch radius smooth 45 degree elbow||1 foot|
|6 inch radius smooth 90 degree elbow||1 foot 9 inches|
|8 inch radius smooth 45 degree elbow||1 foot|
|8 inch radius smooth 90 degree elbow||1 foot 7 inches|
|10 inch radius smooth 45 degree elbow||9 inches|
|10 inch radius smooth 90 degree elbow||1 foot 6 inches|
The size and maximum length of the exhaust duct shall be determined by the dryer manufacturer’s installation instructions. The code official shall be provided with a copy of the installation instructions for the make and model of the dryer at the concealment inspection. In the absence of fitting equivalent length calculations from the clothes dryer manufacturer, Table M1502.4.4.1 shall be used.
Where space for a clothes dryer is provided, an exhaust duct system shall be installed. Where the clothes dryer is not installed at the time of occupancy the exhaust duct shall be capped or plugged in the space in which it originates and identified and marked “future use.”
Range hoods shall discharge to the outdoors through a single-wall duct. The duct serving the hood shall have a smooth interior surface, shall be air tight, shall be equipped with a back-draft damper, and shall be independent of all other exhaust systems. Ducts serving range hoods shall not terminate in an attic or crawl space or areas inside the building.
Single-wall ducts serving range hoods shall be constructed of galvanized steel, stainless steel or copper.
2. The underfloor trench in which the duct is installed is completely backfilled with sand or gravel;
3. The PVC duct extends not more than 1 inch (25 mm) above the indoor concrete floor surface;
4. The PVC duct extends not more than 1 inch (25 mm) above grade outside of the building; and
5. The PVC ducts are solvent cemented.
Exhaust hood systems capable of exhausting in excess of 400 cubic feet per minute (0.19 m3/s) shall be provided with makeup air at a rate approximately equal to the exhaust air rate. 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.
(a) Four hundred cubic feet per minute or less; or
The wholehouse mechanical ventilation system shall provide outdoor air at a continuous rate of not less than that determined in accordance with Table M1507.3.3(1).
CONTINUOUS WHOLE-HOUSE MECHANICAL VENTILATION SYSTEM AIRFLOW RATE REQUIREMENTS
|DWELLING UNIT |
|NUMBER OF BEDROOMS|
|0 – 1||2 – 3||4 – 5||6 – 7||> 7|
|Airflow in CFM|
|1,501 – 3,000||45||60||75||90||105|
|3,001 – 4,500||60||75||90||105||120|
|4,501 – 6,000||75||90||105||120||135|
|6,001 – 7,500||90||105||120||135||150|
INTERMITTENT WHOLE-HOUSE MECHANICAL VENTILATION RATE FACTORSa, b
|RUN-TIME PERCENTAGE IN EACH 4-HOUR |
Local exhaust systems shall be designed to have the capacity to exhaust the minimum air flow rate determined in accordance with Table M1507.4.
|AREA TO BE EXHAUSTED||EXHAUST RATES|
|Kitchens||100 cfm intermittent or 25 cfm continuous|
|Bathrooms-Toilet Rooms||Mechanical exhaust capacity of 50 cfm intermittent or 20 cfm continuous|