The extractor is on. It's making noise. But the kitchen still smells of whatever you cooked two hours ago. This is one of the most common kitchen complaints and the fix is usually cheap and takes five minutes.
The most likely cause: a clogged carbon filter
If your cooker hood is a recirculating type (it sucks air in and blows it back out into the kitchen, rather than venting outside through a duct), it has a carbon filter. That filter's job is to absorb cooking odours from the air before it gets recirculated.
Carbon filters have a limited lifespan. The activated carbon inside gradually saturates as it absorbs VOCs. Once it's full, air passes through but the odour stays in it. The hood is effectively just a noisy fan at that point.
General replacement guidance is every two to four months for regular cooking. Some manufacturers say annually, some say quarterly. Check your hood's manual. But if you've had the hood for more than six months and never touched the filter, it's almost certainly done.
How to check if the filter is the problem
Two-minute test:
Turn the extractor on to its highest setting. Hold a sheet of kitchen roll or a tissue near the grille underneath. If the suction feels noticeably weak, or the tissue barely gets pulled toward the grille, either the grease filter is clogged (blocking airflow) or the carbon filter is spent (not absorbing odour).
Start with the grease filter. Pull it out (usually clips or slides) and check if it's thick with grease. If it is, wash it in hot soapy water or run it through the dishwasher. That alone might fix the airflow.
If the grease filter is clean but the hood still doesn't remove smells, it's the carbon filter.
How often should you replace the filter?
Depends on how much you cook and what you cook. Frying and high-heat cooking saturates carbon faster than boiling or steaming.
Rough guide:
- Cook daily with frying: every 1-2 months
- Cook daily, mostly boiling/baking: every 2-4 months
- Cook a few times a week: every 4-6 months
- Rarely cook: every 6-12 months
You can't clean a carbon filter. Unlike grease filters, which can be washed, carbon filters must be replaced when they're saturated. The carbon is spent and no amount of washing brings it back.
How to replace a cooker hood carbon filter
Most recirculating hoods have the carbon filter behind or adjacent to the grease filter. The process is usually:
- Switch the hood off and unplug it (or switch off at the fuse)
- Remove the grease filter (clips or slides out)
- Locate the carbon filter behind it. It's usually a rectangular or circular pad
- Unclip or twist the old filter out
- Fit the new one in the same position
- Replace the grease filter
- Done
Some hoods use brand-specific filters with proprietary clips. Others accept universal cut-to-size carbon filter pads. If you're not sure which yours needs, check the model number on the hood and search for it on Amazon.
| Product | Fits | Price |
|---|---|---|
| Universal carbon filter pads | Most recirculating hoods — cut to size | £5–8 |
| Bosch/Siemens DHZ5346 | Bosch and Siemens recirculating hoods | £15–22 |
| Elica CFC0140343 | Elica hoods (common in UK kitchens) | £12–20 |
Universal pads are the cheapest option and work well in most hoods. You cut them to fit the filter housing. Brand-specific filters are pre-shaped and sometimes have denser carbon, but at two to three times the price.
When the filter isn't the problem
If you've replaced the carbon filter and the hood still doesn't remove smells, check these:
Recirculating vs ducted. Make sure you actually have a recirculating hood. Ducted hoods vent outside and don't use carbon filters (they use grease filters only). If yours vents outside and cooking smells still linger, the problem isn't the hood. It's that the air in the kitchen needs longer to clear, or the hood isn't powerful enough for the room.
Hood too small for the hob. The hood should be at least as wide as the hob. A narrow hood over a wide hob misses the vapour from the outer burners.
Installed too high. Hoods work best when mounted 65-75cm above an electric hob or 75-80cm above gas. Higher than that and the rising vapour disperses before it reaches the intake.
Fan speed too low. Using the lowest speed for heavy frying isn't enough. Boost mode exists for a reason.
Ducting issues (for ducted hoods). If the duct run is long, has multiple bends, or uses flexible ducting that's kinked, airflow drops significantly. A 90-degree bend in the ducting can reduce extraction by 20-30%. Three bends and your powerful hood is performing like a budget one.
When to replace the extractor fan entirely
If your hood is more than 10-15 years old, underpowered for your kitchen size, or a basic unbranded builder's model, replacing it might make more sense than keeping up with filter costs.
For smaller kitchens, a wall-mounted fan with a timer (like the Manrose MF100T) is a cheap upgrade that keeps air moving after you've finished cooking. For a proper hood replacement, look at the extraction rate in m3/h — you want at least 400 m3/h for a standard kitchen, more for open-plan.
| Product | What it is | Price |
|---|---|---|
| Manrose MF100T (with timer) | Wall-mounted fan, keeps running after you switch it off | £25–40 |
| Vent-Axia Lo-Carbon Revive | Continuous running with boost mode | £40–65 |
For other ways to deal with cooking smells beyond the extractor, see our full guide.
If the smell is reaching other rooms even with a working extractor, we cover containment strategies here.
Prices checked April 2026. Prices may vary.
