How to Degrease a Range Hood and Its Filters

Why this matters

A range hood is the add-on that turns a good deep clean into a damage claim. The filters are usually aluminum, the degreaser on most trucks is caustic, and caustic on aluminum leaves a dull gray-black stain in minutes that no amount of polishing brings back. The client paid for clean filters and got a pair that look burned. The opposite failure is quieter: a filter soaked, rinsed and put back still tacky, which re-loads with grease within weeks and tells the client the service did nothing. The method below gets the chemistry right for the metal, does the hood body while the filters soak, and ends on a test you can feel.

Know what you are looking at before anything gets wet

Look up under the hood with a flashlight before you touch it.

  HOOD UNDERSIDE, looking up (wall at top)
  +--------------------------------------------+
  |  GREASE CHANNEL or TRAY (some at front)    |
  |============================================|
  | +-----------------+  +-----------------+   |
  | | FILTER 1        |  | FILTER 2        |   |
  | | rear edge sits  |  | baffle or mesh  |   |
  | | in channel      |  |                 |   |
  | +-----[CLIP]------+  +-----[CLIP]------+   |
  |   spring latch at front edge of each       |
  |  [ LIGHT LENS ]             [ LIGHT LENS ] |
  +--------------------------------------------+
        front lip, controls on front face

Three filter types, three answers:

• Mesh filters are layered expanded aluminum in an aluminum frame. They take the soak below, with an aluminum-safe degreaser only.
• Baffle filters are angled blades, usually stainless and sometimes aluminum. A magnet tells you which: it sticks to most kitchen stainless and never to aluminum. Stainless baffles tolerate a stronger degreaser; aluminum baffles get the same care as mesh.
• Charcoal (carbon) filters sit in recirculating hoods that vent back into the room, usually behind or in addition to a mesh filter. They are not washable. Water ruins the carbon. They get replaced on the maker's schedule, and if the client wants that done, it is a parts item on the ticket, not a cleaning step.

The grease channel is the trough the filters drain into, front or back depending on the hood. Some hoods have a removable grease cup at one end of it. It holds the heaviest, oldest grease in the hood.

The light lens is glass or clear plastic. Plastic lenses can craze (develop fine cracks) under solvent and some strong degreasers, so the lens gets dish soap, not degreaser.

Make it safe to reach into

Electrical. Turn the fan and light off at the hood controls, then remove power before you wet-wipe inside the hood body, where the light sockets and fan wiring are. Many under-cabinet hoods plug into a receptacle in the cabinet above; unplug it. A hardwired hood goes off at its breaker, which the client or the panel directory should identify. Then press the fan and light buttons: nothing should run or light. If you cannot find the breaker and the hood is hardwired, clean the filters and the outside only, and leave the interior for a visit when power can be removed. Water dripped into a live socket is a shock and a short.

Heat. The cooktop below must be off and cool to the touch, and the hood lamps must have cooled, because halogen lamps run hot enough to burn. If the client just cooked, start elsewhere in the kitchen.

Chemical. Degreasers, especially caustic ones, are an eye and skin hazard. Splash goggles and chemical-resistant gloves go on before you mix, per the product SDS section 8, because working overhead puts drips and spray at face level. Do not spray degreaser upward into the hood; spray the cloth.

Gas cooktop. Lay a dry towel across the burners before wiping overhead. Degreaser dripped into a burner port or onto an igniter can cause poor ignition later, and drips onto sealed burners stain them.

The procedure

1. Pull the filters and the grease cup. Press each clip, let the front edge drop, and slide the filter forward out of its rear channel. Hold it level: old grease runs out of the frame when it tips. Set filters on a towel or straight into the sink. Skip the level hold and you drip grease across the cooktop and floor and spend the next ten minutes cleaning that instead.

2. Test the degreaser on the filter frame first. Put a few drops of the mixed solution on a back corner of one frame and wait a minute. Any darkening, gray bloom or chalky white on aluminum means stop and switch to a milder product or a hot dish-soap soak. This is the shelf rule that every new chemical gets a hidden spot first, and on aluminum it takes sixty seconds and saves a pair of filters.

3. Soak in hot water with an aluminum-safe alkaline degreaser. Fill the sink, or a utility tub if the sink is too small, with the hottest tap water available and mix the degreaser to the label's dilution for heavy grease. Fully submerge the filters and let them soak for the time the label gives. Hot water matters: grease softens as it warms, and the degreaser emulsifies softened grease far faster than cold, congealed grease. Why the "aluminum-safe" label matters: strong caustic (sodium hydroxide is the common one) attacks aluminum itself, not just the grease, and the gray-black oxide it leaves is permanent. If the label does not say aluminum, assume it is not.

4. Wipe the hood interior and the channel while the filters soak. With power off, wipe the inside of the hood body with a cloth dampened (not dripping) in the same solution, working from the back toward you so drips fall toward the open front where you can catch them. Scrape the grease channel with a plastic scraper first, then wipe. Empty the grease cup into a bag for the trash, never into the drain, because hood grease solidifies in pipes. Wash the light lens separately in warm water and dish soap. Skip the channel and the clean filters drain onto the old grease, and the hood smells the first time it heats up.

5. Agitate, then rinse hot. After the soak, work mesh filters with a soft nylon brush along the direction of the mesh, both faces. Baffle filters get the brush down each blade channel. Rinse under hot running water, flushing from the clean side back through the loaded side, until the water runs clear. Why soft: a stiff or wire brush tears mesh layers and leaves sharp edges.

6. Judge by touch, not by shine. Pinch the mesh with a gloved hand. A clean filter feels like bare metal: dry-squeaky when wiped, no drag. A tacky feel means emulsified grease still sits between the layers, and that filter goes back for a second soak. Hold it up to a light: light should come through evenly across the face. Dark blotches are packed grease.

7. Dry fully before reinstalling. Shake out, towel off, and stand the filters on edge to drain. A filter put back wet drips onto the cooktop, and the first fan run pulls that moisture into the hood body. Do the stainless exterior while they dry, following 'Stainless Steel Care' and wiping with the grain.

8. Reinstall and restore power. Slide each filter's rear edge into its channel, lift the front, and let the clip seat with an audible snap. Tug gently: a seated filter does not move. Put the lens back, refit the grease cup, plug the hood in or switch its breaker back on, and run the fan on each speed and the light. Why the tug: a filter on one corner of its clip falls onto the cooktop the first time the client brushes it with a pot.

Worked example: a 30 inch under-cabinet hood, two mesh filters

Deep clean add-on, single-family kitchen, gas cooktop, family that fries several times a week. The filters are aluminum mesh (magnet does not stick), with an amber, sticky film and a dark crust at the rear edges. The hood plugs into a receptacle in the cabinet above. The truck's degreaser is labeled safe for aluminum, with a heavy-duty line on the label that reads 1:16.

The mix. The sink holds about 3 gallons with both filters submerged. At 1:16, one part concentrate goes into 16 parts water ('Dilution Ratios and Ounces per Gallon Card' owns the arithmetic). Here: 128 ounces per gallon of water divided by 16 is 8 ounces of concentrate per gallon, so 3 gallons takes 24 ounces. Check from the other side: 24 ounces into 384 ounces of water (3 times 128) is 384 divided by 24, which is 16. The two agree.

The frame test. A few drops on a back corner, one minute: no change in color. Proceed.

The run, in order:

RANGE HOOD - 30 IN UNDER-CABINET     MIN
-----------------------------------  ---
Unplugged in cabinet; fan + light      2
  buttons pressed, nothing runs
Towel over burners; filters out level  3
Frame test, 1 minute, no darkening     2
Soak started (label: 15 min)           1
Interior + channel + lens, during      15
  soak (cup emptied to trash bag)
Brush + hot rinse, both filters        6
Touch test: filter A clean,            1
  filter B tacky at rear 2 in
Filter B second soak, 10 min           10
  (stainless exterior meanwhile)
Rinse B, touch test passes             2
Drain + towel dry, on edge             5
Reinstall, plug in, all speeds         2
-----------------------------------  ---
Total                                  49

Adding the column: 2 + 3 + 2 + 1 + 15 + 6 + 1 + 10 + 2 + 5 + 2 is 49 minutes. The first soak's 15 minutes is not a separate row because the interior wipe filled it exactly. The second soak's 10 minutes was covered by the stainless exterior.

Why filter B failed the touch test. It sits over the front burner the family fries on, and its rear two inches had the heaviest crust. One soak softened the surface grease and left the packed layer between the mesh sheets. The temptation is to scrub harder; the right move is a second soak, because brushing hard enough to clear packed mesh is hard enough to tear it.

What went in the job file. "Hood: 2 aluminum mesh filters, aluminum-safe degreaser 1:16, frame tested OK. Right filter needed 2 soaks. Recommend filters every visit for this household; at this loading, quarterly is too long." That is a scope note for the office, which owns how it gets priced.

What would change the call. A stainless baffle filter could have gone into a stronger degreaser if its label allows stainless, and some baffle filters are listed by the hood maker as dishwasher-safe; aluminum mesh in a dishwasher often darkens from the detergent, so check the hood manual before offering it. A recirculating hood with a charcoal filter would have had the mesh pre-filter cleaned and the charcoal left alone and noted. And had the frame test darkened, the job switches to a long hot dish-soap soak, which works slower but cannot hurt the metal.

How you know it is done

Both filters pass the pinch test with no drag and show even light through the face. The hood interior and channel wipe clean on a fresh white cloth. The lens is clear and back in place. The filters are seated, a gentle tug does not move them, the fan runs on every speed, the light works, and the towel came off the burners clean. If any filter shows gray or black spots that were not there before, stop and tell the client the same day rather than letting them find it.

References

• Degreaser label and SDS (dilution, soak time, metals it is safe on, PPE)
• Range hood owner's manual (filter type, removal, dishwasher guidance, charcoal replacement)
• See related: Dilution Ratios and Ounces per Gallon Card
• See related: Stainless Steel Care
• See related: Appliance Interior Cleaning Standard