504.8.4 Duct length.
The maximum allowable exhaust duct length shall be determined by one of the methods
specified in Sections 504.8.4.1 through 504.8.4.3.
504.8.4.1 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 504.8.4.1.
TABLE 504.6.4.1 504.8.4.1
DRYER EXHAUST DUCT FITTING EQUIVALENT LENGTH
DRYER EXHAUST DUCT FITTING TYPE EQUIVALENT LENGTH
4″ radius mitered 45-degree elbow 2 feet 6 inches
4″ radius mitered 90-degree elbow 5 feet
6″ radius smooth 45-degree elbow 1 foot
6″ radius smooth 90-degree elbow 1 foot 9 inches
8″ radius smooth 45-degree elbow 1 foot
8″ radius smooth 90-degree elbow 1 foot 7 inches
10″ radius smooth 45-degree elbow 9 inches
10″ radius smooth 90-degree elbow 1 foot 6 inches
For SI: 1 inch = 25.4 mm, 1 foot = 304.8 mm, 1 degree = 0.0175 rad.
504.6.4.2 504.8.4.2 Manufacturer's instructions.
The 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. Where the exhaust duct is to be
concealed, the installation instructions shall be provided to the code official prior to the
concealment inspection. In the absence of fitting equivalent length calculations from the
clothes dryer manufacturer, Table 504.6.4.1 504.8.4.1 shall be used.
504.6.5 Length identification.
Where the 504.8.4.3 Dryer exhaust duct is concealed within the building construction, the
equivalent power ventilator length.
The maximum length of the exhaust duct shall be identified on a permanent label or tag. The
label or tag shall be located within 6 feet (1829 mm) of determined by the dryer exhaust
duct connection. power ventilator manufacturer's installation instructions.
504.6.6 504.8.5 Length identification.
Where the exhaust duct equivalent length exceeds 35 feet (10 668 mm), the equivalent
length of the exhaust duct shall be identified on a permanent label or tag. The label or tag
shall be located within 6 feet (1829 mm) of the exhaust duct connection.