• Dryer vent systems shall be independent of all other systems and shall convey the moisture to the outdoors. 
• Terminations shall be a minimum of three feet from property line and 12" above the ground and not exhibit any type of screen.
• Vents and duct connections shall not be connected with sheet-metal screws or fastening means which extend into the vent. 
• Exhaust vents shall be equipped with a back draft damper and no screen. 
• Vents shall be constructed of minimum 0.016-inch-thick (0.406 mm) rigid metal ducts, having smooth interior surfaces with joints running in the direction of air flow and having a minimum interior diameter of 4".
• Flexible duct and the respective connectors shall not be concealed within the construction.
• The maximum length of a 4-inch (102 mm) diameter exhaust vent shall not exceed 25 feet (7620 mm) from the dryer location to wall or roof termination, and shall terminate with a full opening exhaust hood.  A reduction in maximum length of 2.5 feet for each 45-degree bend and 5 feet for each 90-degree bend shall apply.  Installations where this length is exceeded shall be installed in accordance with the manufacturer's installation instructions.
• 2003 IMC - International Mechanical Code (section 504) and 2003 IRC - International Residential Code (section 1501). Summary: The International Mechanical Code article 504.6 stipulates the requirements for Domestic clothes dryer ducts. In brief, the maximum length of duct permitted is 25 ft. This maximum length should be reduced by 2.5 ft for each 45-degree bend and 5 ft. for each 90-degree bend. The duct should be a minimum nominal size of 4 inches in diameter and shall have a smooth interior finish.
• Click here to view the "Dryer Venting Guidelines".

  I read a mechanical code that indicated a "cleanout" was required in the clothes dryer exhaust.  What does that mean?
Answer Correct, the new "International Mechanical Code" specifically states on "Section 504.3 Cleanout - Every vertical riser shall be provided with a means of cleanout." The intent of this code element is to provide an accessible means to remove the lint accumulation that would fall vertically (settle) to a low spot in the vertical run.  If a means already exist to access this, (i.e., the usual ell through the drywall or a Dryerbox) then a cleanout is not required. Our engineers' professional opinion is that The Dryerbox meets the requirements as a cleanout opening for the dryer exhaust system.  Click here to download/print our "Sealed Engineers Letter" regarding the cleanout issue.