Guide

Why your chimney extract is not working

Every bend in an extract duct costs airflow. The fix is a layout decision, not a bigger chimney.

Why your kitchen chimney duct does not clear smoke

You turn on your kitchen chimney, but smoke still hangs in the room. Fumes drift into the hall, and an oily film settles on your dining table and ceiling. You run the exhaust fan on maximum speed, yet the smell of frying spices stays inside for hours.

This happens because of bends in the exhaust pipe. Every time air turns a sharp corner inside a pipe, it loses speed. Air rubs against the inner walls of the duct, creating friction. A bend acts like a barrier. When smoke hits that turn, flow stalls and pushes fumes backward into the room.

Fixing this after construction costs money. You cannot fix bad duct routing by buying a larger suction unit. If you try to correct it later, you have to break through finished masonry, cut through false ceilings, or replace ruined cabinetry. You pay twice: first for the failed installation, and then for demolition, masonry repairs, and repainting.

The rules for kitchen ducts and clearances

Our professional practice enforces a straight rule: place the hob against an external wall and route the duct straight out with no bends. The outlet must discharge on the leeward side of the building.

Our practice also requires that kitchen smoke never shares air with the living space without a ducted extract. Recirculating filters do not manage Indian cooking. Smoke, steam, and vaporised oils must exit the building directly.

To make this extract work, your counters and work areas must follow tested clearances. Our practice sets the clear dimensions for kitchen joinery and circulation:

The National Building Code Part 8 also requires habitable spaces to have ventilation openings on two different faces. A mechanical fan alone is not ventilation. You need outdoor air movement to supply fresh air while the duct removes fumes.

How to lay out your kitchen, duct, and living areas

You must pick your hob wall before you choose counter shapes or cabinet finishes. If you do not anchor the hob to an external wall first, your duct will end up long, bent, and ineffective.

Your hob must sit against an external wall so the duct pipe passes straight through the wall to the outside. Zero bends gives the fan full extraction power.

The duct must discharge on the leeward side. Leeward means the side facing away from the prevailing wind. At latitudes between 8°N and 16°N, prevailing breezes push air against the windward side of your house. If you run an exhaust duct into the windward wall, external wind pressure blows against the exhaust stream. Smoke stalls in the pipe and backs up into your kitchen. Discharging leeward lets the natural low pressure suck the exhaust outdoors.

Orientation also controls heat. At 11°N, the sun rises at about 6° and sets at about 18°. The eastern wall receives low-angle morning sun for an hour or two. The western wall takes that same low angle in the late afternoon, when outdoor air temperatures reach their daily peak and building materials are hot. Placing the kitchen in the south-east corner matches traditional placement and climate geometry. It lets you direct ductwork straight through an external wall away from afternoon sun, while keeping your hob on an outside face. North light at 8° to 16°N carries no direct sun, which provides cool, even light for preparation areas.

Your room layout must follow a strict order. Our practice establishes the sequence: kitchen, then dining, then living.

This sequence determines whether an open kitchen works with heavy cooking. Open kitchens look spacious on plan sketches, but heavy Indian cooking releases airborne oil, turmeric, and high-heat spices. If you run an open kitchen without a direct, straight external duct, that smoke mixes directly with living room air. Grease settles on sofa fabrics, curtains, and television screens.

If you want an open kitchen, the kitchen must still sit on an external wall, with the hob vented straight outside and the dining room acting as a buffer before the living room. If you cannot place the hob on an external wall, keep the kitchen closed behind a solid door.

The mistake this layout prevents

The most common mistake is placing the cooking hob on an internal wall or an open island. When the hob sits on an internal wall, the duct must run across the ceiling to reach the outside.

A duct crossing an interior ceiling requires at least two ninety-degree bends. It also requires several metres of pipe. That pipe traps grease, collects condensation, drops air speed, and forces greasy vapor into your ceiling structure.

This mistake is expensive to fix. In our practice, construction cost anchors for 2026 across India range from ₹1,600 to ₹2,000 per square foot for a basic finish, ₹2,000 to ₹2,800 for standard work, and ₹2,800 to ₹4,500 or more for premium construction. A 995 square foot house built at ₹1,700 per square foot costs about ₹16.9 lakh.

If your walls are built with 230 mm burnt clay brick, 200 mm concrete block, or 450 mm stabilized earth, cutting into finished masonry to re-route an exhaust duct weakens the structure. In stabilized earth or lime walls, pipes and conduits must be built in as the walls rise, because you cannot chase them later without damaging the material. Breaking open ceilings, core-cutting external walls, replacing burnt-out chimney motors, and replastering ruined chases can add tens of thousands of rupees to your finish work. Getting the duct path straight on the initial drawing costs nothing.

What this means for your plan

Check your sketch to verify that the cooking hob sits directly against an exterior wall on the leeward face. Ask your designer to show the exact path of the exhaust pipe through the wall with zero elbow bends before you approve the layout. Make sure your floor plan maintains the kitchen to dining to living sequence so cooking fumes never enter your primary seating space. The design tool applies these duct positions and clearance rules automatically when it draws your plan.

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