Kitchen Chimney Not Sucking Smoke? How to Find the Cause

First, measure the suction you actually have

Before you take anything apart, get an honest baseline. Two thirty-second tests tell you a great deal.

• The paper test. Switch the chimney to its highest speed and hold a single sheet of newspaper flat against the filter. A healthy chimney holds it there without your hand. If it falls straight off, you have almost no suction. If it clings weakly, you have partial suction — which points at grease rather than a dead motor.
• The smoke test. Light an incense stick and hold it near the edge of the hood. Watch which way the smoke drifts. It should pull in decisively across the whole width. If it pulls in at the middle but not at the ends, the hood is too small or too high for your hob, not faulty.

Note the result. Partial suction and zero suction lead to very different conversations with a technician.

Are the filters clogged?

This is the cause in most cases, and it is entirely free to fix. Indian cooking — tadka, deep frying, long gravies — puts far more oil into the air than the cooking most chimneys were designed around, so the real cleaning interval is much shorter than any manual states.

• Baffle filters — the curved steel panels in most Indian kitchens. Soak them in very hot water with a strong degreasing detergent for twenty to thirty minutes, then scrub. Hot is the operative word; grease does not shift in lukewarm water however hard you scrub. Every three to four weeks with daily cooking.
• Mesh or cassette filters — layers of fine aluminium mesh. They trap oil well and clog fast. Same treatment, more often, and replace them once the mesh is permanently matted.
• Charcoal filters — only on recirculating chimneys with no duct. These cannot be washed at all. They are replaced, and an exhausted one means the unit is doing essentially nothing. If your chimney has no duct to the outside and you have never replaced a charcoal filter, that is very likely your entire answer.
• Auto-clean or filterless models — oil is flung into a collector cup. Empty it on the same schedule. Also check the cone and blower behind it, because these units still accumulate grease where you cannot see.

Refit only when the filter is bone dry. Repeat the paper test afterwards.

Is the duct or the outlet flap blocked?

If clean filters did not restore the pull, the air has somewhere else it is failing to go. This is where a lot of Delhi flats lose their suction permanently.

• Check the external flap. Most ducts end in a hinged flap or shutter on the outside wall. They jam shut with old grease, paint, or a pigeon nest. Switch the chimney on and check from outside or from a window that the flap opens. A jammed flap means zero extraction no matter how good the motor is.
• Count the bends. Every ninety-degree bend in the duct costs suction. A duct that snakes around a false ceiling to reach a distant wall may be losing most of its performance to the route itself. Shorter and straighter is dramatically better.
• Look at what the duct is made of. The corrugated flexible aluminium pipe supplied with most units is convenient and restrictive. It also collects grease in every corrugation and eventually narrows. Replacing a long flexible run with rigid pipe is one of the biggest single improvements available.
• Check the duct actually leaves the building. A surprising number terminate inside a false ceiling, a closed cabinet, or a shaft that is itself sealed. If yours vents into a dead space, no amount of servicing will help.
• Check for a crushed or disconnected pipe. Especially after any carpentry or false-ceiling work in the kitchen.

When is it the blower or the motor?

Only after filters and duct are ruled out. Two very different symptoms point here.

• Grease loaded onto the blower wheel. The impeller inside the hood collects a thick coating over the years. That extra weight unbalances it, cuts airflow and makes the unit noticeably louder while pulling less. This is what a professional deep clean removes, and it is the most common paid fix. It is not a home job — the unit has to come apart.
• A motor that has genuinely failed. Sounds different: humming with no rotation, a burning smell, intermittent running, or a unit that trips the MCB. A motor that is dying usually announces itself with noise and heat before it stops.
• Speed control or push-panel failure. If only some speeds work, or the touch panel responds erratically, the control board is at fault rather than the motor. Voltage fluctuation is hard on these panels.
• Wrong-sized chimney for the kitchen. If the chimney has never worked well since installation, and everything is clean, the unit may simply be underpowered for the hob, or mounted too high above it. A hood mounted well above the recommended height loses a lot of its effectiveness.

What to do next, and what Delhi adds to the problem

Two local factors make this fault arrive faster here.

• Cooking style. Daily frying and tempering load a filter several times faster than the usage the maintenance interval assumes. Treat monthly filter washing as the default, not the exception.
• Dust in the air. Delhi dust sticks to greasy surfaces and turns them into a hard crust that ordinary detergent will not touch. Left long enough, a filter reaches a state where soaking no longer restores it and replacement is the only option. Cleaning early is cheaper than cleaning late.

If clean filters and a working flap have not restored the pull, the next step is a professional strip-down of the hood and blower. Our chimney cleaning cost guide explains what a deep clean involves, and our chimney care tips cover the routine that keeps it from coming back. While a technician is in the kitchen, the wall behind the hob and the cabinet tops are usually in a worse state than the chimney — see our kitchen deep cleaning guide.