Dryer Vent Cleaning & Vent Cap Replacement - Burlingame, CA

## Severe Lint Accumulation and Code Violations Found in Burlingame Home During a residential dryer vent inspection in Burlingame, the technician discovered a duct system in urgent need of attention. Interior photos of the ductwork revealed heavy, compacted lint coating the walls of the flexible metal transition duct and the main exhaust run, reducing the effective airflow diameter significantly. Per issue code `LINT_BUILDUP_SEVERE`, this level of occlusion (greater than 50% blockage) represents the leading cause of residential dryer fires, with the U.S. Fire Administration attributing approximately 2,900 home dryer fires per year to lint accumulation. Left unaddressed, the restricted airflow would force the dryer to overheat, shorten its service life, and increase energy consumption by up to 30%. The pre-cleaning inspection also identified several installation deficiencies on the existing transition duct. Joints had been secured with standard cloth duct tape rather than UL 181B-FX listed metal foil tape or approved clamps, a clear violation of IRC M1502.4.2. The duct also featured a low-slope horizontal run that promotes lint trapping and moisture pooling. The existing exterior termination cap was a plastic louvered cover showing significant staining, dust accumulation, and reduced damper function. A plastic louvered or screen-type cap can restrict exhaust flow and is not compliant with IRC M1502.3, which requires an approved termination cover that opens freely and does not impede airflow. ## Full Cleaning and Compliant Vent Cap Installation Completed The technician performed a complete rotary brush and compressed-air cleaning of the entire exhaust system, clearing the compacted lint from the transition connector at the dryer outlet through to the exterior termination point. The old non-compliant transition duct was replaced with a new 4-foot UL 2158A-listed flexible transition hose (UL listing 47AV), properly sized for the dryer exhaust outlet and secured with metal band clamps at each connection point. This replaces the previously taped and improperly routed semi-rigid duct. At the exterior wall, the technician removed the original plastic louvered cover and installed a new Innovate valve-style dryer vent cap. The wall flange (base cover) was bedded in silicone caulk on its back face before mounting, providing a weatherproof seal on the concrete foundation wall and preventing water intrusion behind the flange. Silicone was selected specifically for this outdoor application due to its durability against moisture and temperature cycling. The new cap features a backdraft damper that opens freely under exhaust pressure and closes to block cold air, pests, and moisture when the dryer is off, bringing the termination into compliance with IRC M1502.3. The completed system now provides a clean, unobstructed exhaust path from the dryer to the outside of the Burlingame home.