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Range hood: Recirculating vs. Exhaust

06/02/2025

8 min.

All BORA cooktop extractor systems are available in both recirculating and vented versions. Both systems effectively remove steam, odors, and grease particles. The main difference lies in the airflow.

Which option is best suited for your kitchen depends in no small part on the layout of the space. In our guide, we explain how they work and help you make the best choice for your needs.

Contents

Technical Difference Between Recirculation and Exhaust Ventilation
Advantages and Disadvantages of Exhaust and Recirculation Systems
Factors influencing the purchase decision
FAQ: Recirculating vs. Exhaust

What is the difference between recirculation and exhaust modes on a range hood?

An exhaust hood vents the drawn-in air to the outside. The system is connected to an exhaust duct system that includes a wall box, which leads outside through an opening in the building envelope. This opening may be in the exterior wall, the roof, or the basement.

Here's how the system works:

Cooking fumes (steam) are vented outside through the wall-mounted vent. Backdraft dampers in the exhaust duct prevent outside air from flowing back into the building. Depending on the installation situation, special exhaust air accessories such as an exterior wall vent, a brick vent, or a flat roof vent may be used.

Exhaust air systems are more complex to install than recirculation systems and are typically used in new construction. They completely remove smoke and odors from the cooking area. Thanks to intelligent airflow technology, less warm indoor air is drawn out of the house than is the case with traditional range hoods installed above the stove that vent to the outside.

In our video, you can see how the BORA exhaust system is routed, using the BORA Classic 2.0 as an example:

With a recirculating range hood , the air stays inside the living space. The range hood draws in air contaminated with cooking and frying odors as well as grease particles, filters it through grease and activated carbon filters, and releases it cleaned back into the kitchen environment. Here's what that looks like in detail:

The BORA grease filter removes grease particles from cooking fumes, while the BORA odor filter traps odor particles.

For the BORA Pure product family, there are two high-performance filters to choose from: the GFES eSwap odor filter and the GFESP eSwap odor filter Plus.

Changing the eSwap filter is a breeze—simply insert it from the top through the air intake opening, without having to remove any drawers or base panels.

The odor filters should be replaced after 150 hours of operation or, depending on cooking habits, approximately one year, to ensure effective ventilation. In contrast, the ULBF and ULB3X air purification units do not need to be replaced until after 300 operating hours (approximately 1.5 years) and 600 operating hours (approximately 3 years), respectively

Recirculating ventilation systems are easier to install than exhaust ventilation systems and are often preferred in smaller apartments, rental properties, and in passive, low-energy, and nearly zero-energy buildings.

Thanks to the auto-run feature, the range hood continues to run on a low setting for about 20 minutes after cooking is finished. This allows the activated carbon to dry thoroughly and bind odor molecules more effectively.

BORA Cooktop Exhausts With recirculation or exhaust

Modular and Compact Systems – An Overview of All BORA Cooktop Exhaust Systems

To the product overview

Exhaust or recirculation: Pros and cons at a glance

Both range hood systems have their advantages, which you should take into account when planning your kitchen:

System	Advantage	Disadvantage
Recirculating air	Simple & affordable installation Flexibility in planning kitchen islands Suitable for passive & low-energy homes Energy stays in the room	Regular replacement of the odor filter required Humidity remains in the living space
Exhaust air	Low maintenance (no filter replacement required) Humidity is transported outside	Potential energy loss in winter, as warm air is extracted and transported outside Limited suitability for passive and low-energy homes Structural opening required

Which is better for me: an exhaust hood with venting to the outside or a recirculating hood?

Both systems have their advantages. Our comparison will help you make a decision:

Recirculation mode is the better choice if	Exhaust mode is the better choice if
✓ you want a straightforward installation.	✓ the installation of an exhaust system is structurally feasible (such as in a new building).
✓ Structural conditions do not allow for an exhaust air system.	✓ Steam and moisture are to be completely removed from the living space.
✓ Regular filter changes are not a problem.	✓ Maintenance should be kept to a minimum.
✓ No permit for exhaust air is available (e.g., in rental apartments).	✓ You frequently sear food, as smoke cannot be filtered.
✓ Maximum energy efficiency is important.	✓ You want to avoid having to change the filter.

Factors influencing the purchase decision

From installation to maintenance, there are key factors to consider before deciding on a BORA cooktop extractor system with recirculation or venting. Our checklists are here to help you:

Installation: Take structural conditions into account

It is not always possible to implement an exhaust ventilation system. Please check:

For a new building, whether the piping and wall penetration for an exhaust ventilation system are feasible and permitted: In some new buildings, exhaust vents are prohibited. The point of contact is the architect or developer.

As a tenant, you must obtain the landlord’s consent—after all, this is a structural alteration that requires the owner’s approval.

Since exhaust air options are customized for each installation, the duct system (BORA Ecotube) and the wall box are not included with BORA cooktop extractor systems.

You get everything from a single source. The components (cooktop extractor, cooktop, fan, filter, duct, and wall box) of the BORA cooktop extractor systems are perfectly coordinated with one another.

Energy efficiency of exhaust air and recirculated air

In winter, valuable energy can be lost through an exhaust hood, as warm air from the heating system escapes outside along with cooking fumes.

Please note: Due to the nature of the system, official energy labels are only available for the exhaust air models.

This can have a negative impact on the energy balance, especially in passive houses or highly insulated low-energy homes.

Construction experts therefore recommend that, in highly insulated new buildings, range hoods should use recirculation rather than exhaust ventilation.

In older buildings, however, exhaust ventilation is usually recommended, as there are often significant temperature differences in older buildings that can lead to condensation.

Maintenance of exhaust and recirculation systems

For effective odor removal when operating in recirculation mode, a special odor filter—the activated carbon filter—is required in addition to the grease filter.

As the activated carbon filter is used, its surface area eventually becomes unable to absorb and bind odor molecules. That is why the odor filter should be replaced regularly.

The operating times are specified in the user or installation manual for the cooktop range hood system. BORA cooktop extractor systems provide a timely notification on the control panel (filter service indicator) when it is time to replace the filter.

BORA cooktop extractor systems in exhaust mode are equipped only with a grease filter, but do not have an additional activated carbon odor filter, since cooking fumes are vented to the outside.

Air exchange in range hoods: Caution around fireplaces

Range hoods and cooktop vents with exhaust mode remove cooking fumes from the room. Nevertheless, it is important to ensure that the air is replaced with fresh air.

This can be done through an open window or automatically via a controlled ventilation system .

This is especially true when operating a fireplace, a gas furnace, or a coal-fired heater in the same room—otherwise, the negative pressure created by the exhaust air could draw hazardous flue gases into the room.

In buildings with particularly tight airtightness, this risk exists even with fireplaces that are independent of the room air—that is, heating appliances such as wood-burning stoves that draw their combustion air through a separate supply line (e.g., an air-flue chimney).

A window contact switch eliminates this risk by allowing the range hood to turn on only when the window is open, ensuring that enough fresh air can flow in. Window contact switches such as the UFKS are available from BORA.

Recirculating range hoods filter out grease and odors, but not the water vapor produced during cooking: That is why adequate ventilation is important.

Your BORA partner will assist you with the planning

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FAQ on Exhaust or Recirculation

We answer the most frequently asked questions about exhaust air and recirculation systems here.

Can any range hood be set to recirculation mode?

Many range hoods can be converted to recirculation mode, provided that the necessary filters can be installed. Check the manufacturer's specifications for detailed information.

What do I need to keep in mind when installing an exhaust hood with an exhaust vent?

Keep the exhaust duct as short as possible, and make sure to use the correct pipe diameter, which is specified for yourBORAcooktop extractor system,as well asensuringtight connections. Depending on the installation situation, special exhaust air accessories such as exterior wall, brick, or flat roof vents are used during the initial installation. When installing fireplaces, ensure that they are installed properly by qualified professionals (use Home-In/Out interfaces).

Do you need an activated carbon filter for a recirculating range hood?

Yes, an activated carbon odor filter is essential because it filters odors out of the air before it is recirculated into the room. The filter must be replaced regularly, as it becomes saturated over time and loses its effectiveness.

Can a recirculating range hood be converted to an exhaust system at a later date?

Provided that the structural conditions for breaking through a wall and the necessary conduits are in place, this is generally technically feasible. On the unit itself, onlyafilter unit is removed and replaced with an appropriate exhaust duct.

How does the noise level compare between recirculation and exhaust modes?

Exhaust systemscan beslightly quieter, since the air does not pass through an activated carbon filter. However, this depends heavily on the duct layout, which determines the noise level. Thanks to modern technology, however, this difference is barely noticeable in everyday life—both options allow you to carry on a conversation at a normal volume right next to the cooktop.