Why Is My Kitchen Exhaust Hood Not Pulling Smoke?
A hood that has stopped pulling is usually mechanical: a slipped or broken fan belt, a seized fan motor, grease loaded into the filters and duct, or a damper stuck shut. A hood also cannot exhaust air the kitchen is not replacing, so a make-up air unit that is off will stop it clearing — which is why the doors get heavy and the kitchen gets hot.
What your exhaust hood is doing, and how long you have
A hood that has stopped pulling affects the whole kitchen, not just the cook line. Find the symptom that matches.
- Call today Smoke hanging over the line during service
- Call today Fan silent with the switch on
- Stop using it Grease dripping from filters or the plenum
- Call today Squealing or rattling from the roof fan
- Monitor it Doors hard to open, or they pull shut on their own
- Monitor it Kitchen noticeably hotter than it used to be
- Monitor it Filters visibly loaded or missing
A kitchen exhaust hood that stops pulling smoke, steam, and grease affects more than comfort — it affects air quality, grease accumulation, and fire safety. When the hood is not clearing the line, the kitchen gets hot, smoky, and unsafe. This page covers the common causes, what to check, and when to book a service call.
Why a hood stops pulling
A kitchen exhaust hood that is not pulling usually has one of these root causes:
- Broken fan belt — the belt that drives the exhaust fan can snap or slip. The motor runs but the fan does not turn.
- Failed fan motor — the motor can burn out or fail to start. No fan rotation means no exhaust.
- Grease buildup in the duct — accumulated grease narrows the duct and restricts airflow. This is also a fire hazard.
- Stuck or misadjusted damper — the damper in the duct controls airflow. If it is stuck closed, the hood cannot pull.
- Make-up air imbalance — if the make-up air unit is not supplying replacement air, the hood cannot exhaust effectively (negative pressure).
- Clogged grease filters — baffle or mesh filters clogged with grease restrict airflow through the hood.
What you can check in the kitchen
- Listen to the fan on the roof — is it running, or is the motor humming without turning the fan?
- Check the grease filters under the hood — are they caked with grease? Remove and clean them if so.
- Check the damper — is it open, or stuck in a closed position?
- Check the make-up air unit — is it running and supplying air to the kitchen?
- Look for grease buildup at the duct access panel if one is accessible.
When the hood needs a technician
If the filters are clean, the damper is open, and the make-up air is running but the hood still does not pull, the issue is likely a broken belt, a failed motor, or duct buildup. A belt is a quick fix; a motor or duct cleaning requires a technician. Book a service call — a hood that does not clear is a fire safety issue, not just a comfort issue.
How a technician checks a hood
Exhaust and make-up air work as a pair, so the check covers both — a hood can be perfectly healthy and still not pull.
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Confirm the fan is turning, and turning the right way
A slipped or broken belt is the most common mechanical cause. A fan running backwards after electrical work moves almost no air while sounding entirely normal.
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Pull and inspect the filters
Loaded baffle filters choke the hood. Missing filters are worse than dirty ones — grease goes straight into the duct, where it becomes a fire load rather than a cleaning job.
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Check make-up air is actually arriving
A hood cannot exhaust air the kitchen is not replacing. If the make-up air unit is off or its damper is shut, the kitchen goes negative — which is why the doors get heavy and the hood stops clearing.
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Look at the damper and the duct run
A stuck damper or a duct heavily loaded with grease cuts flow at a point nobody can see from the kitchen. This is also the check that flags a cleaning overdue for safety reasons.
Who you’re asking
This is written from the work Pierre Refrigeration Services does every week in commercial kitchens across Metro Atlanta. Owner Don Pierre has spent 20 years in commercial refrigeration and HVAC and established the business in 2014. Refrigeration and HVAC are handled by the same company, which is why these guides treat a fault as a building problem rather than one trade’s problem.
Related questions
- Why is the kitchen hot if the hood is running?
- Often because it is running too well relative to the make-up air. Exhaust without replacement air pulls conditioned air out of the dining room and outside air in through every gap — and the cooling never catches up.
- Is a hood that pulls weakly a fire risk?
- It is a signal worth acting on. Weak flow usually means loaded filters or a greased duct, and both are the conditions a hood fire needs. It is a cleaning and inspection question as much as a mechanical one.
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