Hood Not Drawing Smoke: Duct Size, Damper and Makeup Air
A hood not drawing smoke leaves steam and cooking smoke rolling out past a newly installed hood, however loud its fan runs.
Mon–Sat, 8am–8pm
- 5 checks before you book
- 5 questions that narrow it
- 6 causes, cheapest first
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What it
usually means.
A hood is a fan pulling air through a duct, and a newly installed one that does not capture smoke is usually telling you about its duct, its height or the house around it rather than its motor. The fan rating on the box is measured with a free path; a duct smaller than the outlet, a run with several elbows, a long climb to the roof or flexible foil in place of smooth metal all cut that airflow sharply, and the fan gets louder while moving less. A backdraft damper still taped shut from the factory, or a wall cap with a stuck flap, stops the flow almost entirely. A hood mounted higher than the maker's range lets smoke spread past its edges before it is caught, and one narrower than the cooking surface below it misses the outer burners. Then there is the house itself. A tight, modern house cannot give up air it does not have, and a strong hood without makeup air stalls, whistles at the door gaps and can pull fumes back down a water heater flue. A recirculating hood sends the air back into the kitchen by design. A motor that hums without turning, on a new hood, belongs to the maker's warranty or our sister repair site.
The 6 causes, cheapest first
Answer these first
Does the fan sound strong while the smoke still escapes, or does it sound weak as well?
Is the hood ducted outside, or does it recirculate through charcoal filters?
Outside, does the wall or roof cap flap open when the fan runs?
How high is the hood above the cooking surface, and is it as wide?
Does the smoke get better with a window cracked open nearby?
Check these
before you book.
Hood not drawing smoke: 5 checks, and none of them costs anything.
Run the fan on high and go outside to see whether the cap flap opens and air pushes out.
Crack a window near the kitchen and see whether the hood captures smoke better.
Look up inside the hood, with the fan off, for tape on the damper or a reducer at the outlet.
Also worth checking
- Measure the height from the cooking surface to the hood and compare it with the instructions.
- On a recirculating model, make sure the charcoal filters are fitted and the packing is removed.
How soon does it need a visit?
A weak hood can wait for a visit. If a gas water heater or a fireplace is in the house and the hood seems to pull air down its flue, stop using the hood on high and have it checked soon.
The causes,
cheapest first.
6 things hood not drawing smoke: duct size, damper and makeup air turns out to be, from no makeup air for a strong fan to a fan motor that does not turn.
The cost guide-
01 no installation
No makeup air for a strong fan
A large fan in a tight house has nothing to pull against. Cracking a window shows the difference at once; a makeup air system is planned to the local code, and an HVAC contractor usually fits it.
-
02 lowest
A damper still taped or stuck shut
Many hoods ship with the damper taped for transport, and a wall cap flap can stick. The tape is removed, the flap freed, and airflow at the cap is checked with the fan running.
-
03 low to moderate
A hood mounted too high or too narrow
Smoke spreads past a hood set above the maker's height or one narrower than the cooking surface. The mounting height is corrected within the range the instructions give.
-
04 moderate
A reducer choking the outlet
A new hood connected to an old, smaller duct is choked. The duct is enlarged to the size in the instructions where it can be reached, and the reducer is removed.
-
05 moderate
Too many feet of duct and too many bends
Each elbow and each foot of duct costs airflow. The route is shortened and straightened where possible, and smooth metal replaces flexible sections.
-
06 moderate
A fan motor that does not turn
A hum with no airflow at all on a new hood points to a motor or a capacitor. It is the maker's warranty, and after it, our sister repair site.
What else
it could be.
Most often confused with igniter clicking after a gas hookup: air in the line or a wet cap, then burning smell on the first run: when it is normal and when to stop.
All problemsCodes that come with it
Check Vent / Vent BlockedGE Profile · Vents and ductingd90LG · Vents and ductingC90Samsung · Vents and ducting
Also related
The makes
it happens on.
37 makes on this site; hood not drawing smoke: duct size, damper and makeup air can show up on any of them. Each mark opens that make's own page.
All 37 brandsHood Not Drawing Smoke: Duct Size, Damper and Makeup Air,
where we come out.
9 metros, each with its own page.
All service areasTampa BayFL · 31 areas
Miami / South FloridaFL · 47 areas
New York MetroNY · 75 areas
HoustonTX · 36 areas
ChicagoIL · 50 areas
Los AngelesCA · 95 areas
San DiegoCA · 31 areas
Questions about
hood not drawing smoke: duct size, damper and makeup air.
Why does the hood get louder but not stronger on high?
How high above the cooking surface should the hood hang?
Can a hood be vented into the attic?
Does a recirculating hood remove smoke?
Back to your everyday
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