A dryer vent should be a maximum of 25 feet long, if it runs straight with no turns or bends, according to the International Residential Code. For every 90-degree turn the duct must make to reach the venting location, five feet must be deducted from the normal maximum length.
A 45-degree turn requires a 2.5 feet deduction from the maximum length. Using a dryer vent that is too long could allow lint to accumulate and create a fire hazard. In addition to limiting the length of the duct, it is important to ensure the vent is not crushed against a wall or the floor.