Range Hood: Weak Suction

A range hood that used to clear smoke and steam within seconds but now leaves a haze hanging over the stove has usually lost suction gradually, which makes the decline easy to overlook until cooking becomes genuinely unpleasant. The good news is that weak suction is rarely caused by the fan motor itself.

Grease filters are the first and most common cause. Metal mesh filters trap airborne grease particles as they pass through, and that trapped grease gradually solidifies and blocks airflow through the mesh. Manufacturers recommend washing metal filters monthly under normal use — soaking them in hot water with degreasing dish soap, or running them through a dishwasher cycle, usually restores full airflow immediately.

For ducted range hoods, blocked or crushed ductwork is the next most likely cause. Grease residue accumulates along the interior of the duct over years, gradually narrowing the passage, and flexible foil ducting is especially prone to sagging or kinking at bends, which restricts airflow even when perfectly clean. If your hood has never had its ductwork professionally cleaned, that is a reasonable next step before assuming a mechanical failure.

Check that the exterior wall or roof vent cap is not obstructed by debris, a bird's nest, or a damper that has become stuck in the closed or partially closed position. Dampers are designed to prevent outside air and pests from entering the duct when the hood is off, but a damper that fails to open fully when the fan runs can silently choke off most of your airflow.

If filters are clean, the duct run is clear, and the exterior vent opens properly, a weakening fan motor is the remaining possibility — motors lose efficiency gradually with age and can also develop worn bearings that reduce blade speed. A technician can measure actual airflow with a simple test and compare it to the manufacturer's rated CFM to confirm a motor issue.