A charcoal refill, not a grease filter: who actually needs GNK RHBB FLTR
Reviewed September 2026 · Captivating Cabinets
Prices quoted in this article were read off the grid on the review date; the live price grid on this page governs.
Almost every “this hood has lost its power” call we take ends with somebody searching for a range hood filter replacement, and most of them land on the wrong part. GNK RHBB FLTR, $71.50, is the activated-charcoal refill for the RHBB DCT recirculating kit sold on the duct cover page. It removes smells, not grease, and a hood that vents outdoors never takes one. The grease filters in a vented hood arrived inside the blower insert, and they are washed rather than bought. So the first job on this page is working out which kind of hood you own.
Match the part to the hood you actually have
Every shell in this finish takes one of three Broan-NuTone inserts, and each insert ships with its own grease filter. Whether you ever buy anything after that depends only on where the air goes.
| Your setup | Grease filter | Charcoal | What you keep buying |
|---|---|---|---|
| Vented outdoors, 250 or 400 CFM insert | Washable mesh, supplied with the insert | None | Nothing — dish soap and hot water |
| Vented outdoors, 600 CFM insert | Hybrid baffle, supplied with the insert | None | Nothing |
| Recirculating through RHBB DCT | The insert’s own mesh or baffle | One in the kit | GNK RHBB FLTR at $71.50 per change |
If you are in the first two rows, you can close this page: a lingering smell on a vented hood means it is not being run long enough or the duct run is losing air, which is a question for the installer. The grey in the product title is only the collection, by the way. The refill lives inside the kit, out of sight, and it is the same part whatever the cabinets are painted.
Weak and loud? Check the metal filter before ordering anything
A grease filter is a deliberate restriction: the air turns and the oil does not, so the oil lands on metal instead of in the pipe, and the fan was sized to pull against that resistance. As the filter loads up, the resistance climbs past what the fan was designed for. Airflow at the burners falls, the motor labours and the hood gets noticeably louder — which is why a neglected hood sounds like it is working hard while achieving very little.
Grease the filter can no longer hold travels on into the duct, coats the pipe along its length and becomes a fire path that is miserable to clean. On a recirculating hood it has a second victim: it smears onto the carbon and shortens that refill’s life. So the free diagnosis comes first. Pull the metal filter, hold it up to a window or a lamp, and see whether light comes through. If it does not, that is your answer, and it costs nothing.
What the carbon does, and why it ends up in the bin
Activated charcoal is riddled with microscopic pores, and odour molecules stick to the walls of those pores as air passes through. When the available surface is used up, the filter is full and stays full. Water does not unstick what has been captured — it just soaks and degrades the bed — and baking it or vacuuming it does not revive it either, whatever the internet suggests. A spent refill is replaced.
The symptom is quiet. The hood sounds the same and still moves air; it simply stops cleaning it, and the kitchen smells of dinner an hour later or the next morning. People blame the fan. If the metal filter is clean and smells are hanging around, the carbon is the next thing to check, and a saturated bed also adds resistance, so a tired refill can make the hood feel weaker as well.
Budgeting the refills against the cost of a duct
The change interval is set by the kit’s instructions and then stretched or shortened by how you cook — frequent frying uses carbon up faster than boiling and baking. We do not print a single number because there is not one. What can be done is the sum. At $71.50 a change, two changes a year is $143.00, and three is $214.50; over a decade that is roughly $1,430 to $2,145 spent on something that goes in the bin.
Put that figure next to the one-off cost of running a duct, a cap and a damper to the outside, which your contractor can quote. When the two are close, the duct usually wins: it is paid for once, needs nothing afterwards, and removes the heat, moisture and burner gases that charcoal leaves in the room. Our design team can check whether a route exists before you commit to refills for the life of the kitchen.
Washing the metal filters without ruining them
This is the maintenance every hood in this finish needs, vented or not. Fill a sink with water as hot as the tap runs, add dish soap and a generous spoon of baking soda, and leave the filters to soak for twenty to thirty minutes before touching them — the soak does the work, and a soaked filter brushes clean in seconds. Use a soft brush along the mesh or the baffle channels, rinse well, and then dry them completely before refitting. A damp filter pushed back into a canopy is how a metal frame starts to corrode.
What to avoid: wire wool and scouring pads, which scratch the metal and leave it holding grease more readily; oven cleaner or caustic degreaser on aluminium, which discolours it for good; and bending a mesh filter back into shape, since the mesh works through its geometry. Whether yours can go in the dishwasher is in the insert’s manual — check there first rather than finding out from a dulled filter.
While the filters are out, wipe the stainless liner, and treat the painted shell more gently: the care guide covers what is safe on it, which is mild soap, a soft cloth and nothing solvent-based. And never run the hood with the filters out. Grease that would have been caught goes straight into the blower housing, the one part of the assembly you cannot take to the sink.
Common questions
- Does a vented range hood need GNK RHBB FLTR?
- No. It is the charcoal refill for the RHBB DCT recirculating kit. A hood that vents outdoors sends odours outside and only ever uses the washable grease filter that came with its insert.
- Is the replacement filter a grease filter?
- No. It is activated charcoal and removes cooking smells on a recirculating hood. Grease is caught upstream by the insert’s own metal filter — mesh on the 250 and 400 CFM inserts, a hybrid baffle on the 600 — which is not sold on this page.
- Can a charcoal range hood filter be cleaned?
- No. Odour molecules stay stuck in the carbon’s pores, and washing, baking or vacuuming does not release them; water mainly damages the bed. When it stops removing smells it is replaced.
- How often does the charcoal need changing?
- As the kit’s instructions direct, adjusted for how much you fry. The reliable sign is smells hanging around after cooking with a clean grease filter in place. At $71.50 a change, two a year is $143.00.
- Why has my range hood got weaker and louder?
- Almost always a clogged metal grease filter: the fan is pulling against far more resistance than it was sized for. Hold the filter up to a light; if you cannot see through it, wash it. On a recirculating hood, a saturated charcoal refill is the next suspect.
- Are the insert’s grease filters dishwasher safe?
- Check the insert’s manual before trying it. A half-hour soak in hot water with dish soap and baking soda, a soft brush and a full dry does the job with no risk to the finish of the metal.
Keep reading
The guides behind the numbers on this page.
- Range Hood CFM: How Much Ventilation Your Kitchen Needs
Which filter each insert ships with, and the recirculating kit this refill belongs to.
- How to Clean and Care for Your Kitchen Cabinets
What is safe on the painted shell while the metal filters soak.
- Cabinets for Property Managers and How to Standardize Unit Turns
Filter washing and charcoal changes as a line on the turnover checklist.
- How Much Do Fabuwood Cabinets Cost in 2026? Real Prices by Line
Where the hood, its insert and its running costs sit in the whole budget.
