Design, construction, and workmanship shall comply with accepted engineering practices and shall be of such character as to secure the results sought to be obtained by this code. CMC 309
Exhaust ducts shall be constructed of sheet metal or other non-combustible material 0.0195”.
Shall be installed with a lint-controlling means.
Exhaust ducts shall be installed with a clearance of > 6” to combustible materials. < 6” shall be protected by table 303.10.1.
Where ducts pass through walls, floors, or partitions, the space around the duct shall be sealed with non-combustible material.
Multiple installations shall be made in a manner to prevent adverse operation due to back pressures that are capable of being created in the exhaust systems. The exhaust fan shall operate continuously or shall be interlocked to exhaust air where a clothes dryer is in operation.
Common Exhaust: Where permitted by the clothes dryer manufacturer’s instruction, multiple clothes dryers shall be allowed to be installed with a common exhaust. The common exhaust duct shall be rigid metal and shall be installed in a fire-resistant rated enclosure per the building code. The duct material shall be of rigid metal with a thickness ≥ 0.02” (24 gauge). The duct enclosure shall be provided with a cleanout opening at the base ≥12” x 12”. The exhaust fan shall be located downstream of branch connections and operated continuously and shall be monitored by an approved means.
