How to Clean a Range Hood Filter (Without Replacing It)
Last month I pulled a range hood filter out of a Stanmore terrace that hadn’t been touched in eight years. I weighed it on the kitchen scales before cleaning — 1.4 kilos of solid baked-on grease laminating the mesh. By the time I’d done my 20-minute laundry trough soak, the filter was back to its factory aluminium colour and weight, and the homeowner thought I’d swapped it for a new one. Right, gear first — and a quick word on chemistry, because most people do one of two wrong things when they finally notice their filter: they bin it and order a new one ($60-80 from appliance parts stores), or they hit it with caustic oven cleaner and ruin the aluminium permanently. Both are unnecessary. Boiling water, bicarb, and a dishwashing tablet will get you factory-fresh aluminium in 20 minutes of mostly walking-away time. Here’s the science.
Gear you’ll need
- Boiling water — full kettle, plus a saucepan if your trough is big
- Bicarb soda — half a cup, supermarket brand fine
- One dishwashing tablet — Finish Quantum, Fairy, or Coles/Woolies own brand
- Laundry trough or a deep tub (kitchen sink works in a pinch, line with a basin to protect the finish)
- A nylon dish brush or old toothbrush
- Microfibre cloth
- Newspaper or an old towel for drips
- Rubber gloves
- NEVER: oven cleaner, caustic soda, ammonia, bleach
Step 1: Identify the filter type before you start
Critical first step. Open the range hood, slide out the filter (button or clip release). Look at it:
- Silver/grey aluminium mesh, multiple layers of crinkly mesh: washable. Use this method. 95% of Aussie hoods.
- Black/dark grey carbon filter, looks like a thick cardboard pad with foam: not washable. Replace it. Common in recirculating (non-ducted) hoods only.
- Stainless steel baffle filter, interlocking metal blades: washable, dishwasher safe. Use this method but skip the dishwashing tablet — it can dull the stainless finish.
If yours is carbon, stop here and order a replacement — running carbon through water just disintegrates the cardboard core. If aluminium or stainless baffle, continue.
Step 2: Lay newspaper around the trough
Hot greasy water will splash. Newspaper or an old towel saves the laundry floor. Take the trough’s plug out and replace it with a fresh seal — most laundry trough plugs are knackered and let hot water drain away mid-soak, ruining the whole job. A new rubber plug is $3 at Bunnings.
Step 3: Boil the kettle and bring water to the trough
You want the filter fully submerged. Start with a kettle of just-boiled water in the trough, then top up from the hot tap until the filter is covered with at least 30mm of water above it. Boiling water is what drives the grease out — lukewarm water won’t do it. Here’s the science — baked-on grease is oxidised polymerised fatty acids that are solid at room temperature. They only become mobile around 60°C and they really start to flow above 80°C. Tap-hot water sits at about 50°C, which is why “soak it in the sink” advice doesn’t work. Boiling water from the kettle into the trough holds it around 75-85°C for the soak duration.
Step 4: Add bicarb soda first, then the dishwashing tablet
Half a cup of bicarb sprinkled over the surface — it’ll fizz on contact with hot water. Drop the dishwashing tablet in. Here’s the chemistry: bicarb is alkaline (pH 9), and alkali plus fatty acid drives saponification — the same reaction that converts oils into soap. The dishwashing tablet adds enzymes (proteases and lipases) plus more surfactant. Together, you’ve got an alkaline degreaser strong enough to lift years of baked-on grease but mild enough to leave aluminium intact. Caustic oven cleaner would do the job faster but it also dissolves the aluminium itself — that’s why it’s banned for this. Definately don’t substitute.
Step 5: Submerge the filter flat
Lay the filter flat in the trough, mesh-side up. Flat orientation matters — water needs to reach all layers of the mesh evenly. Filters propped vertically only get the lower portion properly soaked and you’ll have a half-clean filter at the end. Push it down so it’s fully under the water surface — if it’s floating, weight it with a small ceramic plate or a jar.
Step 6: Walk away for 20 minutes
This is the bit nobody believes. You don’t scrub. You don’t agitate. You walk away. Make a coffee, empty the dishwasher, come back in 20 minutes. The water will be brown — sometimes opaque brown — and the filter will be most of the way clean already. For really horror filters (haven’t been cleaned in 2+ years), top up with another kettle of boiling water at the 20-minute mark and leave another 15. The water needs to stay hot for the chemistry to keep working. Dwell time is everything.
Step 7: Drain and inspect
Pull the plug. Lift the filter out carefully — the mesh can be hot and the filter will drip. Hold it under the hot tap and rinse front and back. Most of the grease will sluice off in obvious brown sheets. Hold it up to the light. You should see daylight through every cell of the mesh — that means the airflow path is clear. If you can’t see daylight through alot of cells, give it another 10-minute soak round.
Step 8: Detail the corners with a brush
The corners and edge frame often have stubborn deposits the soak didn’t fully shift — these are the spots where grease has polymerised hardest because they’re closest to the burner heat. Nylon dish brush or old toothbrush, with a sprinkle of fresh bicarb on the bristles, scrub the corners specifically. Rinse again under hot water afterward. Don’t use steel wool or a stainless scourer — they leave micro-scratches that hold grease worse next time.
Step 9: Dry thoroughly before refitting
Pat dry with a microfibre, then sit the filter on a draining rack or hang it over the trough for an hour to fully air-dry. Wet aluminium pressed against the plastic mounting clips of the range hood corrodes both surfaces — galvanic corrosion of the aluminium and stress-cracking of the plastic. Dry it properly before refitting.
Step 10: Wipe the inside of the hood while you’re there
With the filter out, you’ve got access to the fan housing and the inside of the hood. A microfibre cloth with a mist of Spray & Wipe (or White King’s surface cleaner) wipes the housing clean. Gentle pressure only. Don’t get water into the fan motor or the light fitting — wring the cloth out properly. Refit the dry filter when you’re done. If the fan blades themselves are caked, the fan usually unscrews from the housing for separate cleaning — check the manual for your model.
The dishwasher shortcut
For stainless baffle filters: dishwasher on a hot cycle with rinse aid cleans them perfectly. For aluminium mesh: the dishwasher works but dulls the finish to matte over time (cosmetic only). Carbon filters: never in the dishwasher.
How often is “regularly”?
- Heavy cooking household (Asian wok cooking, frequent frying, daily dinner cooking): every 4-6 weeks
- Average cooking (4-5 dinners a week, occasional frying): every 3 months
- Light cooking (eats out often, mostly microwave/oven): every 6 months
Honest test: pull the filter out and hold it up to a window. If you can’t see clear daylight through the mesh, it’s overdue. A clean filter has substantial airflow visible through it; a clogged one looks solid.
Why a clean filter actually matters — fire risk
Beyond aesthetics, a clogged range hood filter is a measurable fire risk. Trapped grease lining the filter and the duct above is exactly the fuel a stovetop fire wants to climb into. Aussie home insurance claims for cooking fires routinely cite filter cleanliness in the assessment. A 20-minute filter clean every 3 months is genuine fire prevention, same reason commercial kitchens are required by law to have their hoods cleaned quarterly — not for hygiene, for fire prevention. ACCC product safety guidance on cooking appliances flags hood maintenance as a homeowner responsibility.
When you should NOT DIY this
If the filter has caked oil older than 5 years on a commercial-grade range hood (a former cafe conversion home, for instance), the polymerised crust may need professional ultrasonic cleaning — boiling water alone won’t shift it and chemical alternatives risk the aluminium. If you’ve got a recirculating hood with a permanently bonded carbon module, that’s a manufacturer-part replacement, not a clean. If grease has bypassed the filter and is coating the duct all the way to the roof, that’s a flue cleaner’s job — domestic settings rarely need this, but if you’ve inherited a place with a clearly grease-coated duct visible through the hood opening, get it cleaned before the next time you fry. And never DIY-clean a hood that’s been involved in any kitchen fire — the inside may be heat-damaged and the wiring needs licensed-electrician inspection before reuse.
Common screw-ups
- Using caustic oven cleaner on aluminium — pits the metal, ruins the filter within a year.
- Soaking in lukewarm water — grease doesn’t mobilise below 60°C, the soak does nothing.
- Propping the filter vertically in the trough — only the bottom half cleans, you get a half-clean filter.
- Refitting wet — galvanic corrosion of the aluminium against the plastic clips.
- Putting a carbon filter through any wash — disintegrates immediately and blocks the dishwasher pump or the trough drain.
Cost & time
Materials: about $4 for bicarb and a dishwashing tablet — both already in most kitchens. Newspaper or a towel you already own. Time: 25 minutes total, of which 20 minutes is walking-away time. Compared to a replacement filter ($60-80) or a professional kitchen hood clean ($120-180 in Sydney), this is the cheapest fire-prevention chore in the home.
Aluminium mesh filter, 20 minutes, boiling water plus bicarb plus a dishwashing tablet. No oven cleaner, no caustic soda, no scrubbing. Identify the filter type first so you don’t try to wash a carbon filter (impossible) or chemically attack stainless (avoidable). Schedule it every 3 months for active kitchens, every 6 for households that mostly eat out, and the filter never gets bad enough to be a half-day chore. While you’re in deep-clean kitchen mode, the bicarb-only oven method uses the same chemistry and the same dwell-time principle — start them on the same Saturday morning and you’ve done the kitchen’s two worst jobs in one block. And the dishwasher 3-stage filter is the other appliance everyone neglects on the same calendar. Caddy out, let’s go.
