If your range hood isn’t pulling smoke, here’s the most useful thing to know before you spend a dollar: it’s probably not broken. In the vast majority of cases the motor is running fine and the real cause is one of a handful of ordinary, fixable problems—grease-clogged filters, a damper stuck shut, a blocked vent cap, bad or disconnected ductwork, the wrong venting mode, a hood mounted too high, or negative pressure in a tightly sealed home. Motor failure is near the bottom of the list, not the top. So the smart approach is to work through the causes in diagnostic order—free and easy first, expensive and invasive last—which is exactly how this guide is organized. Most people find their fix in the first twenty minutes, without buying a new range hood at all.
First: is it really not pulling, or does it just feel weak?
Before diagnosing anything, confirm the symptom with a simple test. Turn the hood to its highest speed and hold a single square of tissue paper or a strip of paper towel flat against the filter surface. If the hood holds it up with reasonable grip, the blower is moving air and your issue is likely capture, sizing, or usage—not suction. If the paper barely clings or falls straight off, you have a genuine airflow problem, and the causes below apply in order.
Do the same test at the outside vent, if you can safely reach it. With the hood on high, hold a tissue near the exterior wall cap or roof cap. Strong air blowing out means the whole chain works and the trouble is at the capture end. Little or no air outside, while the fan is clearly spinning inside, tells you something between the hood and the outdoors is blocked—a damper, the cap, or the duct itself. That single comparison narrows your search enormously.
The 60-second triage
Fan spins, no air at all: blocked duct, stuck damper, or blocked exterior cap.
Fan spins, weak air: dirty filters, undersized or flexible duct, too many bends, or negative pressure.
Good airflow but smoke still escapes: capture problem—hood too high, too narrow, front-burner cooking, or CFM too low for your cooking.
Fan doesn’t spin at all: electrical or motor—skip to the last section.
Cause 1: Grease-clogged filters (start here—it’s the most common)
Clean or replace the filters
This single cause explains more “my hood lost its suction” complaints than everything else combined. Metal baffle and mesh filters trap grease by design, and as that grease builds up it physically shrinks the openings air must pass through. The decline is gradual, so you never notice a day when it stopped working—you just slowly get used to a hood that does less. Pull the filters out and hold them up to a light. If you can’t see light through the mesh, or the baffles feel sticky, that’s your problem.
Most metal filters are dishwasher-safe; for heavy buildup, soak them in hot water with degreasing dish soap and a scoop of baking soda for 15–20 minutes, scrub with a soft brush, rinse, and—critically—let them dry completely before reinstalling. Then check whether the fix worked by repeating the paper test. If your hood has a cleaning reminder, use it; if not, set a calendar reminder to wash filters monthly if you cook daily, or every two to three months for lighter cooking.
Cause 2: A saturated charcoal filter (ductless hoods only)
Replace the charcoal cartridge
If your hood recirculates rather than venting outdoors, there’s a second filter behind the grease filter: an activated-charcoal cartridge. Unlike metal filters, charcoal is a consumable—it cannot be washed, and washing it destroys it. As it saturates, it becomes an increasingly solid wall of resistance, and airflow drops accordingly. Many people never replace it because they don’t know it exists.
Replace charcoal filters on the schedule in your manual—commonly every few months depending on how much you cook. If your hood has been recirculating for a year or more on its original charcoal, that alone can explain a dramatic loss of suction.
Cause 3: A backdraft damper stuck shut
Free the damper flaps
Ducted hoods have a backdraft damper—a flap or pair of flaps that swing open when the fan runs and fall closed when it stops, keeping out weather, pests, and cold air. There are often two: one at the hood’s outlet, and one in the exterior cap. Over time, grease can glue these flaps shut, or they can jam on a bent hinge. A damper stuck closed produces exactly the symptom “the fan is roaring but nothing is being pulled.”
With the hood switched off at the breaker, look up into the outlet and check that the flap swings freely. Clean any grease off the hinge with a degreaser and confirm it falls back smoothly. Then go outside and watch the exterior cap while someone runs the hood on high—the flaps should visibly open. If they don’t move, that’s your blockage.
Cause 4: A blocked exterior vent cap
Inspect and clear the outside termination
The outdoor end of the duct is the most neglected part of the system and one of the most common hidden culprits. Over the years it can accumulate a thick grease crust, get painted shut during exterior work, become packed with a bird or wasp nest, or have a fine insect screen behind it that clogs solid with lint and grease. Any of these can strangle a perfectly healthy hood.
If you can reach the cap safely from the ground or a stable ladder, open or remove it and look inside. Clear out debris and nests, scrub off grease, and confirm the flaps move. Note that a fine mesh screen behind the cap is a frequent offender—many manufacturers advise against fine screens on kitchen exhaust for exactly this reason, since they clog with grease. If the cap is on a roof or otherwise out of safe reach, this is a job for a professional.
Cause 5: The ductwork itself
If the filters are clean, the dampers move, and the cap is clear—but airflow is still weak—the duct is the next suspect. This is the single biggest determinant of real-world performance, and the place where installers most often cut corners. A powerful hood on bad ducting will always underperform a modest hood on good ducting.
Flexible duct
Corrugated flexible “slinky” duct is the classic mistake. Its ridged interior creates turbulence that dramatically reduces airflow, and those same ridges catch grease that’s nearly impossible to clean—a fire risk as well as a performance one. Rigid, smooth-walled metal duct (galvanized steel or stainless) is what a hood needs. Plastic or PVC duct should never be used for kitchen exhaust at all.
Undersized diameter
A duct narrower than the hood’s outlet chokes it. As a rule of thumb, 6″ suits hoods up to roughly 600 CFM, 8″ for 600–900 CFM, and 8–10″ for 900–1,200+ CFM. A frequent real-world failure is a strong new hood installed onto an old 4″ or 6″ duct left behind by a much weaker unit. The hood is fine; the pipe is the bottleneck.
Too long, too many bends, or crushed
Every foot of duct and every turn adds resistance. Keep the total run under about 30 feet and use no more than three elbows; a single 90-degree bend can add resistance equivalent to roughly 5 to 15 feet of straight pipe, which is why two 45-degree elbows are preferable to one 90 where a turn is unavoidable. Also check for physical damage—flex duct crushed behind a cabinet, or a section that has come apart inside a wall or attic. A disconnected duct is the worst case: the hood pumps hard, but everything discharges into your ceiling cavity instead of outdoors, which produces weak room airflow and quietly causes grease and moisture damage.
Cause 6: The hood is in the wrong venting mode
Check ducted vs. recirculating configuration
Convertible hoods can run either ducted or recirculating, and the setup is done at installation. Two mistakes are surprisingly common. First, a hood connected to a duct but still configured to recirculate—so it’s pushing air through a charcoal filter and back into the room while the duct sits unused. Second, on some models, a knockout panel or blower orientation must be changed for the intended direction; if that step was skipped, the hood fights a closed outlet.
The reverse also matters: a hood set to recirculate but with no charcoal filter installed will pass odors and gases straight back into the kitchen, which feels like “it isn’t pulling anything” even though the fan works. Check your manual for your model’s configuration and confirm it matches your actual setup. For a fuller explanation of the two modes, see our guide to ducted stove hoods.
Cause 7: The hood is simply too small for your cooking
If airflow tests fine but smoke still drifts into the room, you may not have a fault at all—you may have a mismatch. A hood sized for light cooking will visibly lose against a wok or a hard sear. Two numbers matter:
| Your cooking | Airflow you want | How to check |
|---|---|---|
| Electric, everyday | ~300–400+ CFM | About 10 CFM per inch of cooktop width |
| Gas | By heat output | Total BTUs ÷ 100 (60,000 BTU → ~600 CFM) |
| Wok / high-heat frying | 900–1,500 CFM | Plus strong static pressure |
| Island cooktop | Add ~50% | No back wall; exposed to drafts |
Also check width: a hood narrower than your cooktop will always let smoke escape at the edges, no matter how strong the motor. And note that CFM ratings are measured under ideal conditions—a hood rated 900 CFM on a test bench delivers far less through a long, bendy, undersized duct. That gap between rated and real is why static pressure matters as much as the headline number.
Cause 8: Mounting height and capture
Measure the height above the cooktop
Capture efficiency falls off fast with distance. Most hoods are designed to sit 24 to 30 inches above the cooking surface (some allow up to 36). Mounted higher than the manufacturer specifies—a surprisingly common outcome when a hood is fitted to existing cabinetry—the rising plume has room to spread and cool before it reaches the intake, and much of it escapes into the room. If your hood is mounted too high, no amount of CFM fully compensates.
Front burners are the other capture weak point on every hood, because they sit farthest from the intake. If smoke escapes mainly when you cook at the front, that’s expected physics, not a fault: shift to the back burners where you can, and you’ll see an immediate improvement.
Cause 9: Negative pressure—the hood has no air to work with
This one is invisible and frequently misdiagnosed as a weak motor. A hood can only exhaust air that can be replaced. In a tightly sealed modern home, a powerful hood can pull the house into negative pressure—a partial vacuum—where it’s literally fighting to move air that has nowhere to enter. The result feels exactly like lost suction.
Telltale signs: performance is noticeably better with a window cracked open; the hood is stronger when the house is “open” and weaker when everything is shut; you hear whistling around doors; or the hood competes with other exhaust running at the same time (bathroom fans, a dryer, a whole-house fan, or an open fireplace flue). Test it in seconds—open a nearby window a few inches while the hood runs on high. If it visibly improves, you have a make-up air problem, not a hood problem.
Cause 10: The blower and motor
Only now, after everything above, is the motor a likely suspect. A few possibilities:
- A grease-caked impeller. If grease has bypassed the filters over years, the blower wheel itself can build up a heavy coating that unbalances it and cuts airflow. Symptoms: reduced flow plus new vibration or noise. Cleaning the wheel requires disassembly and is often a job for a technician.
- A loose or slipping blower wheel. If it isn’t seated properly on the shaft, the motor spins faster than the wheel—you hear a running motor with little air moved.
- Speed control or electronics. If only some speeds work, suspect the control board or switch rather than the motor. On modern brushless hoods, the electronic controller is a possible failure point—though a quality BLDC motor itself has no brushes to wear out and commonly lasts well over a decade, with bearings as the main long-term wear item.
- Bearings. Grinding or a rising whine along with weaker airflow points to worn bearings.
- No power at all. Before assuming the worst, check the breaker, any inline switch, and—on some models—a thermal cutoff that trips if the hood overheats and resets when it cools.
Cause 11: How you’re using it
Not every fix is mechanical. Some “weak hood” complaints are timing and habit. Turn the hood on before you start cooking, not after the pan is already smoking—once a plume fills the room, no hood can retrieve it. Match the speed to the heat instead of leaving it on low out of habit. Leave it running 10 to 15 minutes after you finish, since fine particles and gases stay airborne long after the last dish. And use the back burners when you can. These cost nothing and often account for most of the perceived difference.
Diagnose by pattern: sudden vs. gradual
When the problem started tells you a lot about where to look.
| Pattern | Most likely causes |
|---|---|
| Gradual decline over months/years | Grease-clogged filters; saturated charcoal; grease building up in the cap, damper, or impeller |
| Sudden loss, nothing changed | Stuck damper; nest or debris in the vent cap; duct disconnected; electrical or control fault |
| Never worked well since installation | Ducting (flexible, undersized, too many bends); wrong venting mode; mounted too high; hood too small; vented into an attic |
| Weak only sometimes | Negative pressure (windows shut, other fans running); using low speed; front-burner cooking |
| Noisy but weak | Turbulence from bad duct; unbalanced or grease-caked impeller; failing bearings |
Your step-by-step checklist
- Paper test at the filter, then at the outside cap, to locate the blockage.
- Wash the grease filters; replace charcoal if recirculating.
- Check both dampers swing freely—at the hood outlet and the exterior cap.
- Inspect the outside cap for grease, nests, paint, and clogged screens.
- Trace the duct: rigid or flexible, diameter, length, bends, crushed or disconnected sections, and where it terminates.
- Confirm the venting mode matches your installation, and that charcoal is present if recirculating.
- Check size: hood at least as wide as the cooktop; CFM matched to your BTUs and cooking.
- Measure mounting height against the manual’s spec.
- Test for negative pressure by cracking a window while it runs.
- Only then suspect the blower, controls, or motor.
When to call a professional
Do it yourself for filters, dampers you can reach, a ground-level vent cap, and configuration checks. Bring in a professional for anything involving ductwork inside walls or ceilings, roof-level vent caps, electrical faults or a hood with no power, blower disassembly, make-up air installation, or any duct discovered venting into an attic or soffit. If you cook on gas and suspect backdrafting, treat it as urgent and make sure you have a working carbon monoxide detector.
Preventing it from happening again
- Wash grease filters monthly if you cook daily—every two to three months for lighter cooking.
- Replace charcoal filters on schedule if you recirculate.
- Inspect the exterior cap annually—more often if you fry a lot.
- Wipe the interior and check the damper when you clean the filters.
- Run the hood every time you cook, starting early and finishing late—less grease in the air means less grease in the system.
If a hood is properly installed and maintained, this whole problem largely disappears; for the ducting and electrical fundamentals behind a good install, see the range hood installation guide.
The bottom line
A range hood that isn’t pulling smoke is usually telling you about a clogged filter, a stuck damper, a blocked cap, or bad ductwork—not about a dead motor. Work the causes in order, from the free two-minute checks to the invasive ones, and you’ll almost always find the fix long before you reach the blower. And if the diagnosis turns out to be that the hood was undersized, badly ducted, or mounted too high from day one, at least you’ll be replacing it for the right reason—with the right size, the right airflow, and a proper duct behind it.
Frequently asked questions
Why is my range hood not pulling smoke?
Most often because the grease filters are clogged, a backdraft damper is stuck shut, the exterior vent cap is blocked, or the ductwork is flexible, undersized, too long, or disconnected. Motor failure is uncommon by comparison. Check the cheap, easy causes first—filters and dampers—before assuming the hood is broken.
Why did my range hood suddenly lose suction?
A sudden loss usually points to a blockage rather than wear: a damper glued or jammed shut, a bird or wasp nest in the vent cap, a duct that has come apart inside a wall or attic, or an electrical/control fault. A gradual decline over months points instead to grease buildup in the filters, cap, or blower wheel.
How do I test whether my range hood is working?
Run it on high and hold a single sheet of tissue against the filter—it should be held firmly. Then hold tissue near the exterior vent cap outside. Strong air inside but none outside means something between the hood and the outdoors is blocked; weak air at both ends points to filters, ducting, or negative pressure.
Can dirty filters really stop a hood from pulling smoke?
Yes—this is the single most common cause. Grease progressively closes the openings air must pass through, and because it happens slowly you never notice a specific day it failed. Washing metal filters in hot water with degreasing soap, or running them through the dishwasher, often restores most of the lost airflow.
Does my range hood need make-up air?
If cracking a window noticeably improves suction, your home is likely too tight for the hood to move air freely. Most codes require a make-up air system once a hood can exhaust more than 400 CFM, especially with atmospherically vented gas appliances, since negative pressure can cause backdrafting. Check your local code.
Is flexible duct really that bad for a range hood?
Yes. The corrugated interior creates turbulence that substantially reduces airflow, and the ridges trap grease that can’t be cleaned—a fire risk. Rigid, smooth-walled metal duct sized to your hood’s outlet is what allows a hood to deliver close to its rated airflow.
When should I replace the range hood instead of repairing it?
Replace it when the hood is fundamentally mismatched—narrower than your cooktop, far too little CFM for how you cook—or when the motor and controls fail on an old unit and repair costs approach the price of a modern, quieter, more efficient hood. If the real problem is ducting or mounting height, replacing the hood alone won’t fix it.
Troubleshooting, duct sizing, and make-up air guidance reflects widely used kitchen-ventilation best practices; requirements vary by jurisdiction. Always follow your model’s manual, switch off power at the breaker before inspecting inside a hood, and use a licensed professional for ductwork, electrical, roof access, and combustion-safety-sensitive work. Gas appliances can produce carbon monoxide—maintain a working CO detector. This article is for general informational purposes.
