Signs Your Restaurant Hood Needs Cleaning

What you can see

• Grease drips from the canopy edge or the filter track. If it is running down onto the line, the plenum behind the filters is already loaded.
• Filters that stay tacky after a wash, or that no longer sit flush and leave gaps in the bank.
• A dark film on the ceiling or wall around the hood. That is exhaust the hood is failing to capture.
• Grease pooling at the rooftop fan base or staining spreading across the membrane — an expensive problem long before it is a fire one.
• Visible build-up inside an access panel. Open one and look; the duct is the honest witness, not the canopy.

What you can feel

• The kitchen runs hotter than it used to at the same output. Reduced exhaust volume is the usual cause.
• Smoke lingers over the line instead of being pulled up and away.
• Doors pull harder or the dining room feels draughty — a symptom of the building's air balance shifting as exhaust performance changes.

What you can hear

• New vibration or rumble from the rooftop fan. Grease loads the wheel unevenly and throws it out of balance, which then costs bearings and belts. See exhaust fan cleaning.
• A fan that sounds like it is working harder for the same airflow.

What you can smell

• Rancid or stale grease odour in the kitchen when nothing is cooking.
• Cooking smells reaching the dining room, guest floors or neighbouring tenants. In a hotel or mixed-use building this usually arrives as a complaint before anyone links it to the exhaust system.

Signs that are about records, not grease

• You cannot produce a dated service record for the last cleaning
• Your last record covers only the hood and filters, not the duct and fan
• You have taken over a kitchen with no service history at all
• An inspection or insurance review is scheduled and nobody knows the system's state

These matter as much as the physical signs. Documentation is a large part of NFPA 96 inspection readiness, and an undocumented system is treated as an unknown one.

If several of these are true

Do not wait for the scheduled date — the interval was wrong. Book a full cleaning of the entire path, get photographs of the plenum, duct and fan, and use what is found to reset the interval. Short-notice options are covered under emergency hood cleaning, and recurring service is how you stop reading lists like this one.