Exhaust hood build up is more than a cleaning issue. When residues accumulate, airflow drops, fire risk rises and energy costs climb. This guide explains the early signs to look for, why build up happens, and the simple steps that keep your system safe, efficient and compliant.
Why Exhaust Hood Build up Matters
- Fire risk from canopy grease deposits: Grease deposits are fuel. A small flare up can spread through the duct if residues are heavy.
- Poor air quality from kitchen exhaust residue: Lingering haze, odours and heat make shifts harder and can trigger alarms.
- Higher costs from restricted airflow: Fan motors work harder against clogged filters and greasy ducts, using more power and wearing out sooner.
- Compliance and insurance: Clean, well maintained systems help satisfy landlord, insurer and council requirements.
Exhaust Hood Build Up: Early Warning Signs
1) Baffle filter blockage: looks matted or sticky
Baffle filters should show clear, open channels. If they look furry, sticky or patched with dark residue, airflow is restricted.
2) Canopy grease drips and brown streaks
Brown lines or tacky drips along seams, light lenses or the front lip of the canopy signal trapped grease above the visible surfaces.
3) Odours linger after service
If the kitchen still smells smoky or oily an hour after close, extraction is not clearing vapours properly.
4) Steam hangs around the cookline
You should see a clear “capture” into the canopy during peak service. If steam spills into the room or rolls past the front, airflow is low.
5) Fan noise changes
Rattling, humming, screeching or new vibration often means unbalanced blades, stretched belts or bearings stressed by residue.
6) Hotter kitchen than usual
If staff complain it feels hotter than last month under the same load, resistance in the system may be rising due to build up.
7) Grease marks on the roof or discharge
Look at the fan cowl and roof sheets. Dark stains or oily patches indicate bypassing grease and saturated filters.
8) Lights and surfaces feel tacky
A quick wipe of the canopy face, switches or light lenses leaves a brown film on a white cloth. That film is airborne grease.
9) Breakers trip or motors smell warm
Fans that run against clogged ducts can overheat. A hot motor smell or nuisance trips need fast investigation.
What Causes Kitchen Exhaust Grease Build Up
- High grease menus: Deep frying, woks, chargrilling and bacon-heavy menus create more aerosols.
- Extended hours: Breakfast through late night service accumulates residues faster.
- Incorrect filter care: Washing filters without degreaser, or not drying them fully, reduces capture and creates odours.
- Make up air issues: Not enough replacement air means the system cannot draw properly and vapours escape the hood.
- Undersized or tired fans: Old motors and belts slip under load, cutting airflow.
- Detergent choice: Harsh caustics can damage aluminium filters, reducing lifespan and effectiveness.
Simple Checks to Spot Exhaust Hood Build Up Today
- White cloth test: Wipe inside the canopy and the first 30 cm of the duct entry. Dark residue means it is time to act.
- Torch test: Hold a light behind a clean, dry baffle filter. If you cannot see good daylight through the channels, it is still clogged.
- Paper test: With the fan on, a sheet of paper should hold to the filter face. If it falls, capture is weak.
- Listen up: New squeals, rattles or vibration need a tech before damage snowballs.
- Roof glance: Check the discharge and cowl for oily stains.
How Often Should a Kitchen Exhaust Be Cleaned?
Every venue is different, but the typical guide looks like this:
- Heavy use (woks, fryers, chargrills): canopy, filters and ductwork monthly to 6 weekly.
- Moderate use (mixed cooklines): every 2 to 3 months.
- Light use (baking, low grease): every 3 to 6 months.
A site inspection will set the right interval for your menu, hours and equipment. Keep a simple log of filter washing and professional cleans, and refer to the [AIRAH Best Practice Guide for commercial kitchen exhaust management] for industry-backed intervals and maintenance steps.
Professional Exhaust Hood Cleaning: Whats Included
- Canopy and plenum degrease to bare metal where accessible.
- Baffle filter clean or replacement with correct detergent and full dry.
- Duct clean as accessible, with before and after photos.
- Fan clean and balance including blades, housing and discharge.
- Motor and belt check for tension, wear and heat.
- Airflow assessment to confirm capture at the cookline.
- Service report you can show your landlord, insurer or auditor.
Prevention Between Services
- Train staff to wash baffle filters at the end of each day and dry fully before refitting.
- Wipe canopy faces, lights and edges after each shift.
- Keep lids on fryers and pots to reduce aerosol.
- Use the right degreaser for your filter material.
- Schedule a weekly quick-check for drips, odours and unusual fan noise.
- Make sure make up air grilles are clean and unblocked.
Based on the Gold Coast or Brisbane? We Can Help
Exhaust Fan and Motor Solutions services commercial kitchens across the Gold Coast, South Brisbane and Brisbane city. We inspect, clean and service exhaust hoods, fans and motors, and provide practical advice to keep you compliant and efficient.
Book an inspection
Need an honest look at your system and a service plan that fits your hours and menu? Our team can visit after hours to minimise downtime. Get in touch with us.
FAQ
How do I know if my filters need replacing rather than cleaning?
If channels are bent, frames are warped or the media stays sticky after a proper clean and dry, it is time to replace.
Can you clean during the night or on a closed day?
Yes. We offer flexible scheduling to keep kitchens operating without interruption.
Do you work on roof fans and motors as well as canopies?
We clean and balance fans, check belts and bearings, and service or replace motors as required.