What cleaning schedule fits your kitchen
A fixed calendar is not the best way to schedule grease filter cleaning. The right interval depends on the fuel, the cooking method, and the hours the hood runs each day. Most commercial kitchens fall into one of three tiers.
- Heavy use, 12 or more hours a day, solid fuel or a wok station: remove and wash the baffle filters every night. Solid fuel deposits a fine, sticky soot that hardens fast and blocks airflow within a single shift.
- Medium use, 8 to 12 hours a day, frying or grilling with oil: clean the filters every 2 to 3 days. A thin amber film is normal after one shift, but a second shift builds a layer that starts to drip.
- Light use, under 8 hours a day, mostly steaming, poaching or holding warm food: once a week is usually enough. Check the underside on day 5. If you see a glossy coating, move the cycle to every 5 days.
- Any kitchen that uses solid fuel, charcoal, or a high-output wok burner stays on the daily schedule regardless of hours. The exhaust temperature and particle load leave no safety margin for skipping a day.
A kitchen with mixed stations follows the rhythm of the dirtiest one. If one section fries while another steams, the whole hood takes the 2-to-3-day cycle. Write the cleaning days into the closing checklist and assign the task to a named person to make the rhythm stick.
What happens when you skip a cleaning cycle
Grease sitting on a baffle filter hardens within days. Once it forms a solid layer, the openings letting air through begin to close. Measured airflow can drop by 30 to 50 percent of the hood’s rated capacity. The fan still spins at the same speed but moves less air because the resistance upstream has increased. Cooking smoke and heat that should leave the kitchen stay in the room instead.
The exhaust motor works against higher static pressure to pull air through the clogged filter. The motor draws more current, runs hotter and wears out faster. Over time, the higher electrical load shows up on the utility bill, and a motor replacement costs far more than a regular cleaning routine ever would.
A filter caked with grease is a fuel source. The flash point of polymerised cooking oil is so low that a flare-up on the cooktop can ignite the filter itself. Once flames reach the duct, the fire is fed by the grease deposit lining the duct walls. A duct fire is the hardest kitchen fire to extinguish because it burns inside an enclosed steel chase that handheld extinguishers cannot reach.
Signs the filter is already overdue for cleaning
A baffle filter that has passed its cleaning interval shows clear physical symptoms. The most obvious is grease dripping from the hood edge or the filter frame onto the cooktop. If you wipe the outer surface of the hood and your fingers come away sticky, the filter is saturated and pushing residue back through the seams.
A smell of rancid grease when the fan is off is another reliable indicator. Heat from idle pilot lights or ambient kitchen warmth releases odors trapped in the clogged filter. You also notice smoke lingering longer than usual at the same fan speed, because airflow has dropped below the design capture velocity.
Pay attention to the fan itself. A lower, labored roar often replaces the normal higher-pitched whine when the motor works against a blocked filter. These signs together mean the filter has stopped protecting the ductwork and is now adding to the fire load.
- Grease beads or drips visible on the lower edge of the hood or the filter frame
- Hood surface feels tacky or sticky when wiped with a dry paper towel
- Rancid oil smell noticeable even hours after cooking has stopped
- Fan noise shifts to a deeper, muffled sound under the same speed setting
- Cooking smoke stays at head height and clears noticeably slower
How to wash a baffle filter safely and without damage
Start by removing the filter from the hood. Hold it over a lined waste bin and tap the frame gently to knock off any loose food particles and solidified grease before they reach your drain. Scrape stubborn buildup with a plastic scraper, never a metal blade that will scratch the stainless steel surface.
Soak the filter in a deep sink or basin filled with hot water and a non-caustic commercial degreaser made for kitchen exhaust parts. Do not use oven cleaner on aluminium baffle filters. Caustic chemicals darken the metal, cause pitting and strip the factory finish that helps grease slide into the drip tray. Let the filter soak for 15 to 20 minutes, or longer for heavy carbon deposits.
Scrub both sides with a soft nylon brush, paying attention to the channels and bends where grease collects. Steel wool and abrasive pads leave scratches that trap soil and make the next cleaning harder. Rinse thoroughly with the hottest water your tap can deliver until the runoff runs clear. Stand the filter upright on a drying rack and let it air dry completely before you slide it back into the hood. A damp filter catches new grease immediately and promotes bacterial growth inside the housing.
Does a dishwasher clean a grease filter properly
A commercial dishwasher can handle a stainless steel baffle filter, but only on a short rinse cycle with no detergent. Dishwasher chemicals are too aggressive for the thin layer of grease you are trying to remove. They strip the surface and leave the metal vulnerable to pitting. Run the filter alone, on a glass or rinse cycle, and keep the water temperature below 60 °C.
Aluminium mesh filters should never go through a dishwasher. The alkaline detergents and high heat oxidize the aluminium within one or two cycles. The metal turns dark grey, develops a rough surface, and the fine mesh can pit through. Once pitted, the filter traps debris that you cannot wash out.
After any dishwasher run, the machine itself will carry a slick of grease on the interior walls and spray arms. You need to run an empty degreasing cycle with a commercial machine cleaner before washing plates or utensils again. Skipping that step transfers a rancid film onto glassware and flatware.
- Stainless steel baffle filters tolerate a short rinse-only cycle without detergent
- Water temperature must stay under 60 °C to protect the filter finish
- Aluminium mesh filters oxidize, darken and pit from dishwasher chemicals
- A full degreasing cycle for the dishwasher is mandatory after washing filters
- Hand washing with warm water and a degreaser remains the safer method for both filter types
- Dishwasher racks can scratch baffle surfaces if the filter is not secured flat
When to replace a filter instead of cleaning it
A baffle filter that is bent, pitted or rusted can no longer do its job. The metal fins are designed to spin grease out of the airstream and, just as critically, to block a flame front from travelling up into the duct. Once the structure is compromised, cleaning it is a waste of time. You need a new one.
Replace a filter immediately when you see any of these defects:
- Baffle blades that are visibly bent, warped or pushed out of alignment.
- Pitting or small craters on the aluminium surface, usually from harsh alkaline cleaners left on too long.
- Rust spots or orange staining on a filter sold as stainless steel, which signals a lower-grade alloy that will keep corroding.
- A filter that still feels sticky or greasy to the touch after two full wash cycles with hot water and a proper degreaser.
- Any filter that has been in daily service for more than five to seven years, even if it looks sound, because metal fatigue in the welds and bends reduces its fire-stopping ability.
A damaged baffle will not stop a flame front. In a flare-up on the cooktop, the filter must cool the flame below the ignition point of the grease in the duct. Cracked or missing metal lets heat and flame pass straight through, which is how a small cooking fire turns into a duct fire. If you are unsure about a filter's condition, pull it down and inspect it in good light. When the metal is no longer solid and straight, the only safe fix is replacement.
How a clean filter affects the whole exhaust system
A baffle filter that is cleaned on schedule catches about 90 to 95 percent of airborne grease before it enters the duct. That layer of grease never reaches the duct walls or the exhaust fan blades, so the duct stays cleaner for months longer. Kitchens that stay on a regular filter cleaning cycle typically schedule a full duct cleaning once or twice a year, while kitchens with neglected filters may need the same service three or four times annually. The cost difference adds up fast when you pay by the linear foot of ductwork.
Grease that bypasses a clogged filter eventually coats the fan motor housing and the impeller. The extra weight forces the motor to draw higher amperage, which shortens its service life. A clean filter keeps the airflow resistance low and the motor running within its rated current draw. The make-up air system also stays in balance because the exhaust rate does not degrade. When the hood pulls air at its designed CFM, the kitchen stays at a stable temperature and the air conditioning unit does not have to fight a negative pressure condition.
FAQ
Can I use oven cleaner on a hood grease filter
No. Caustic oven cleaners attack aluminium and will pit or darken the surface within minutes. Use a non-caustic degreaser labelled safe for aluminium, or hot water with a mild dish detergent for light buildup.
How do I know if the filter is dry enough to put back
Shake it. If water droplets fly off, it needs more time. A damp filter traps new grease instantly and can develop a sour smell. Let it air dry for at least an hour, or wipe it down with a clean cloth before reinstalling.
Does a dirty filter really increase the fire risk
Yes. Grease on a filter ignites at around 370°C, and a flare-up from a pan or a grill can reach that temperature in seconds. A clean filter acts as a flame arrestor. A grease-soaked one feeds the fire and lets it spread into the duct.
Should I clean the hood trough and drain cup at the same time
Yes. The trough that catches drips and the drain cup fill with the same grease and will smell and drip if you skip them. Empty the cup, scrape the trough with a plastic scraper and wipe both with a degreaser every time you wash the filters.
