Recirculation vs Ducting for Vented Hobs: Which Do You Need?

Venting hobs (also called extractor hobs or induction hobs with a built-in downdraft) pull steam, grease and cooking smells down through the cooktop instead of relying on an overhead cooker hood. That design is brilliant for islands and open-plan kitchens — but it only works well if the extraction path underneath is planned properly.

Before you order pipes, bends or a full starter kit, you need one clear decision: will the hob duct outside, or will it recirculate cleaned air back into the room? Get that choice right and the rest of the kit list becomes much simpler. Get it wrong and you can end up with the wrong starter kit for your worktop depth, brand or installation type.

This guide explains the difference in plain English, using the kinds of genuine AEG, Neff, Bosch and Siemens kits stocked in our ducting kits and parts collection, and points you toward the matching venting hobs range when you are still choosing the hob itself.

What ducted extraction means

In a ducted (also called ducted exhaust) installation, the hob’s integrated fan pushes cooking air through a run of ducting to an external outlet. Grease and odours leave the kitchen rather than being filtered and returned.

Brand starter kits for ducted setups typically include the first pieces you need under the worktop. For example, the Neff Z861KE1 ducted exhaust starter kit is specified for worktops at least 60 cm deep and includes a small-radius 90° bend, a connector, a short straight channel and a set of acoustic filters. The product notes that additional ducting components may still be required for a full run to the outside wall.

Ducted extraction is usually preferred when:

• There is a realistic route to an external wall, floor void or ceiling outlet
• You want cooking moisture and smells removed from the room rather than filtered
• The kitchen is heavily used for frying, wok cooking or long batch cooking

The trade-off is planning: you need space for flat channel or rectangular ducting, bends that match your brand’s system, and a properly terminated outlet. Flat-channel parts such as Neff Z861SM1 / Z861SM2 lengths and Z861SB1 / Z861SB4 bends exist precisely because under-cabinet routes are rarely a straight line.

What recirculation means

In a recirculation installation, air is drawn down through the hob, passed through grease and odour filtration, then returned to the kitchen. There is no external wall outlet for the cooking air.

Recirculation starter kits are built for that path. The Neff Z861KR1 recirculation starter kit, for example, is an accessory kit for partly ducted recirculation on cooktops with an integrated ventilation module, for worktops 60 cm deep or larger. It includes a vertical 90° “S” bow, connector sleeves and a 500 mm straight tube element. Siemens offers a similar idea for deeper tops with the HZ9VDKR0 recirculation starter kit, specified for worktops 70 cm deep or larger.

Some kits sit between pure duct-out and pure recirculate. AEG’s M2CKCF01C half-pipe ducting kit is described as a universal kit for hob extractor recirculation models to complete a half-pipe recirculation installation, with rectangular curves, pipe, connections and tape included. Always match the kit wording to your exact hob model — recirculation-ready hobs and duct-out hobs are not interchangeable by accident.

Recirculation tends to suit:

• Kitchens where an external duct run is impractical or not allowed
• Apartment or flat installs with limited external wall access
• Island layouts where a long duct run would be complex or noisy

The ongoing care point is filters: charcoal / odour filters need replacing on a schedule set by the hob manufacturer. Separate cooker-hood recirculation kits (for example Bosch DWZ1GK1U2 for certain hoods) are a different product family from vented-hob recirculation starters — check whether you are fitting a venting hob or an overhead hood before you buy.

Worktop depth and brand systems matter

Two details trip people up more than anything else.

1. Worktop depth. Many Neff, Bosch and Siemens kits are labelled for a minimum worktop depth — commonly 60 cm, with deeper options for 65 cm or 70 cm. Choosing a 60 cm kit for a deep island carcass (or the reverse) can force awkward bends or leave you short of the right radius piece. Compare Z861KR1 (min 60 cm recirculation) with Z861KR0 / HZ9VDKR0-style kits aimed at deeper tops.

2. Brand ducting systems. Neff flat-channel parts, AEG rectangular 220×90 mm pieces (such as M2CKCF05 pipe and M2CKCF09 vertical curve), and Siemens / Bosch channel kits are designed as systems. Mix-and-match across brands only when the manufacturer documentation says the connection is compatible. If you already own a venting hob, start from that brand’s starter kit and then add matching lengths, adapters and bends.

How to decide in five practical questions

1. Can you terminate outside? If yes and the route is short, ducted extraction is usually the cleaner long-term option.
2. Is the hob recirculation-ready or duct-out only? Check the hob specification and installation manual before ordering kits.
3. How deep is the worktop? Match the kit’s minimum depth rating.
4. How many bends will the duct run need? Every bend adds resistance; keep the run as short and smooth as practical, and pick the bend radius your brand specifies.
5. Do you need acoustic filters or adapters? Acoustic filter sets (for example Neff Z811DU0 or the filters bundled in some starter kits) and round-to-flat adapters are common add-ons once the main route is planned.

What to browse next

If you already know you need parts, start with the full ducting kits and parts collection — it covers starter kits, flat channel, bends, adapters and recirculation accessories from AEG, Neff, Bosch and Siemens.

If you are still choosing the cooktop, compare extraction style, width and controls in our venting hobs collection. Once the hob model is fixed, the correct recirculation or ducted starter kit becomes much easier to identify.

Still unsure after reading the manuals? Bring your hob model number and a rough sketch of the under-worktop route. Matching the right recirculation or ducting path first saves returns, re-orders and installation delays — and it is the difference between a quiet, effective venting hob and one that never quite clears the kitchen air the way you expected.