Dryer Vent Cleaning & Inspection in San Francisco, CA

## What We Found Our technician performed a thorough dryer exhaust cleaning and inspection at a residential property in San Francisco. During the exterior evaluation, the existing vent hood was found to be in generally good physical condition, but a critical code compliance issue was identified: the vent cap was missing its interior damper flap entirely. Under IRC M1502.3, all dryer exhaust terminations are required to be equipped with a functioning backdraft damper that opens freely during dryer operation and closes by gravity when the dryer stops. Without that flap, outside air, moisture, insects, and pests can freely enter the duct system when the dryer is not running. The homeowner was informed of the finding and opted to defer the vent hood replacement for now, with the understanding that the current installation does not meet code requirements. ## What We Did In addition to the full duct cleaning, our team installed a new UL 2158A-rated fire duct at this residence. The UL 2158A listing is the recognized safety standard for dryer transition ducts, confirming the material can handle the thermal demands of residential dryer exhaust without melting, sagging, or accumulating lint at an accelerated rate. This upgrade replaces a potential weak point in the system and brings that section of the installation into conformance with IRC M1502.4.3, which governs transition duct materials and limits transition duct runs to a maximum of 8 feet. ## Code Compliance Notes The missing backdraft damper at the exterior termination remains an open item for this property. Per IRC M1502.3, the damper must be present and functional, and the terminal passageway must provide a minimum of 12.5 square inches of open area. Screens at the termination opening are explicitly prohibited by that same section, as they trap lint. The homeowner may wish to schedule a vent hood replacement in the future to bring the full system into compliance. All other accessible portions of the exhaust system were cleaned and inspected as part of this visit. ## Why It Matters The U.S. Fire Administration reports roughly 2,900 home dryer fires annually, with lint accumulation and improper venting as the leading contributing factors. Keeping the exhaust duct clean and ensuring all components, including the backdraft damper, are functioning correctly are the two most effective steps a homeowner can take to reduce that risk. Dryer Vent Specialists is proud to serve San Francisco residents with thorough, code-informed inspections and honest reporting on every visit.