Shared Flue Pipe: How to Prevent Smoke from Entering Your Home

Blog Guides Diagnostics Maintenance and cleaning News and Technologies In the kitchen

May 28, 2025
Tiziano B.
Diagnostics
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Smelling unpleasant odors at home—without having cooked anything—can be incredibly frustrating.

Even worse is finding out that the source is the shared flue system in your building, which carries odors from other apartments’ kitchen hoods directly into your home.

Many people only realize there’s a problem when, for no apparent reason, they start smelling food even though they haven’t cooked, or they feel cold air entering through the hood, even in the middle of winter. Some even report hearing voices or noises from neighboring apartments, transmitted through the shared flue.

These situations are not rare and are a clear sign that the extraction system is shared and not properly insulated. Airflow can travel in both directions, and when other units use their extractor hoods, it can push odors, air, or even sounds into your kitchen system. This isn’t just annoying—it can also affect the hygiene and comfort of your kitchen.

In this article, we’ll explore why this happens and what technical solutions you can adopt to permanently eliminate the problem of unpleasant odors in your home. Keep reading!

Who to Contact If There Are Problems with the Building’s Flue System

If you’re experiencing odors from other apartments coming into your home via the shared flue, it’s important to act methodically.

The first step is to notify the building administrator, whose job it is to collect reports and assess the issue with qualified technicians.

Often, it’s helpful to request a building meeting, where the matter can be discussed with all residents and potential solutions proposed.

This isn’t just a matter of comfort—it’s about mutual respect between neighbors. Before anything else, dialogue and a shared willingness to solve the issue can make all the difference.

But first, let’s look at how to tell whether a flue is shared or privately owned—read on below.

How to Tell If the Flue Is Shared

If you notice unpleasant odors, drafts, or even voices coming from your kitchen hood, it’s very likely that your home is connected to a shared flue, meaning a communal extraction system used by multiple apartments.

How to Solve the Problem

There are two main solutions to address the issue of smoke or odors entering your home:

Install a recirculating filter hood: These hoods do not vent air outside, but instead purify it using activated carbon filters. They’re ideal when using a shared flue isn’t possible—or simply not desired.
Use a backdraft damper (non-return valve): This device allows air to exit your system but prevents smoke or air from re-entering through the shared flue. A backdraft damper can be installed inside your kitchen hood or ductwork.

And where can you find the right damper for your needs? Right on Filtro Cappa. Our online store offers a range of models designed to fit your hood’s duct or motor.

What Problems Does a Backdraft Damper Solve?

A backdraft damper is specifically designed to block reverse airflow, helping to solve a range of common issues:

Eliminates unpleasant odors coming from other apartments connected to the same flue
Blocks the entry of cold air, preventing drafts in your kitchen
Stops the transmission of noises or voices through the duct
Improves the efficiency of your kitchen hood, ensuring that airflow remains one-way only

How a Backdraft Damper Works: Opening and Closing

This valve works completely automatically. Inside, it contains one or two movable flaps mounted on side hinges, which open when the airflow from the hood generates enough pressure. In practice, when you turn on the hood, the air pushes the flap open, allowing fumes to exit toward the outside or into the flue.

As soon as you turn off the hood and the airflow stops, the damper closes on its own. Closure happens either by gravity (in simpler models) or through a small return spring in more advanced models. Some dampers also include rubber seals to improve the seal and reduce vibrations.

There are also magnetic-closing models, equipped with magnets that ensure an even tighter and quieter seal, especially useful in spaces where high insulation is desired even when there’s no airflow.

In general, a backdraft damper doesn’t require frequent maintenance, but it’s good practice to inspect it periodically, especially in kitchens with heavy hood use. Over time, grease, dust, and moisture can build up on the flaps or seals, reducing its effectiveness.

A visual check every 6–12 months, along with a simple wipe-down using a damp cloth and gentle degreaser, will help keep it functioning properly. For spring-loaded or magnetic models, make sure the mechanism moves freely and that the seal remains tight. If a flap comes loose and falls into the duct—or worse, into the hood motor—it can cause serious damage to the motor fan.

So remember to inspect it regularly to avoid costly problems!

Filtro Cappa: Your Trusted Supplier for Kitchen Hood Filters and Spare Parts

If you’re looking for effective solutions to improve the performance of your kitchen hood, Filtro Cappa has you covered. On our website, you’ll find a wide selection of grease filters, carbon filters, backdraft dampers, motors, capacitors, and many other original and compatible spare parts for the leading hood brands.

Rely on our expertise and choose only carefully selected components, with fast shipping and dedicated support. Boost your hood’s performance and make your kitchen a healthier, more comfortable space.

And if you need help with your hood, contact us!

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