Dryer Vent Cleaning & Inspection in San Francisco, CA

## Severe Lint Blockage Found at Exterior Vent Cap During this residential dryer exhaust service call in San Francisco, our technician discovered a severely clogged exterior dryer vent cap. As shown in the before photo, the cap's collar and surrounding roof area were heavily caked with compacted lint and dust, partially blocking the vent opening. This level of buildup is consistent with the [LINT_BUILDUP_SEVERE] condition in our problem catalog: the duct was significantly occluded, restricting airflow well below the 300+ CFM most dryer manufacturers require for safe operation. The U.S. Fire Administration reports roughly 2,900 home dryer fires each year, with lint accumulation as the leading factor, making this the most urgent type of finding we encounter. ## Full-System Cleaning and Camera Verification After documenting the initial condition, the technician performed a complete dryer exhaust cleaning using rotary brush and extraction equipment to clear compacted lint from the full duct run. All duct joints were inspected and confirmed sealed correctly, consistent with IRC M1502 requirements for metal tape or approved clamps at every connection. Following the cleaning, a camera was passed through the entire exhaust system from the dryer connection to the exterior termination cap, confirming no remaining blockages, no separated joints, and no concealed obstructions. The after photo shows the cleaned exterior cap with a clear, open periscope-style flapper and no visible lint debris at the termination. ## Roof Termination Condition and Maintenance Notes The exterior termination cap is mounted on a roof surface that shows visible moss and algae growth typical of San Francisco's coastal climate. While the vent system itself was cleared and verified functional, the surrounding roof area warrants routine monitoring to ensure organic growth does not encroach on the cap opening over time. Per IRC M1502.2, the exhaust system must remain independent and convey moisture directly to the outdoors without obstruction. The cap's backdraft damper flapper was confirmed present and operating by gravity as required under IRC M1502.3. ## Outcome At the conclusion of the job, the dryer exhaust system was fully cleared, camera-verified, and confirmed to be venting to the exterior with all joints properly sealed. San Francisco homeowners with roof-mounted dryer vent terminations are advised to schedule annual inspections given the damp, foggy climate, which accelerates lint compaction and moss growth near the cap opening. Routine annual cleaning is the most effective way to maintain safe exhaust performance and protect against dryer-related fire risk.