Kitchen · start-here stack · 6 quick cards
Kitchen Ventilation: Hoods, Gas and Makeup Air
7 cards · By the Air in the House editors, from Berkeley Lab, International Residential Code, Home Ventilating Institute, EPA · how stacks are made · Updated
What does a kitchen need to clear the air?
Kitchen ventilation has one job: catch smoke, grease, steam and burner fumes right at the stove and send them outdoors, with a hood that is sized, ducted and run on high.
- HVI suggests about 100 cfm per linear foot of range for a wall hood and 150 cfm per foot for an island hood.
- The 2024 IRC sets 100 cfm as the minimum for a kitchen fan that is switched on.
- In LBNL lab tests on the highest setting, hoods caught more than 80% of back-burner exhaust, and two of three caught over 90%.
- EPA says gas stoves are a main indoor source of nitrogen dioxide and advises an exhaust fan vented outdoors over them.
- Under IRC M1503.6, a hood over 400 cfm needs makeup air in homes with certain fuel-burning appliances.
- LBNL knows of no home recirculating hood that claims to remove CO or water vapor.
AI-made picture, not a photo of a real house Source the documents listed on this stack's sources card
Next What does kitchen ventilation need to do?↓What does kitchen ventilation need to do?
It needs to pull cooking pollutants out at the stove before they spread through the house. LBNL researchers found that individual cooking events can push short-term PM2.5 above 300 µg/m³, and that kitchen ventilation works best when it sits closest to the source.
The code floor is modest: 100 cfm when the fan is switched on, in both the IRC and ASHRAE 62.2. For always-on kitchen exhaust they part ways: 25 cfm in the IRC, five air changes per hour of the kitchen's volume in ASHRAE 62.2. The 2024 IRC exhaust chapter also says the duct must be smooth inside, airtight, fitted with a backdraft damper and kept separate from other exhaust. Your local code may differ.
Stacks on this How much airflow does a range hood need? Ducted or recirculating: which hood should you get?
Kitchen exhaust options compared Option HVI or code guidance What it removes Watch for Wall hood, ducted outdoors 100 cfm per foot recommended (40 minimum) Smoke, grease, moisture, burner gases Makeup air above 400 cfm Island hood, ducted outdoors 150 cfm per foot recommended (50 minimum) Smoke, grease, moisture, burner gases Reaches the 400 cfm makeup-air line sooner Over-the-range microwave hood Code minimum 100 cfm 40–85% front, 60–100% back burner (LBNL) Front-burner capture runs lower Ductless (recirculating) hood Allowed if listed and other ventilation exists Some grease; no claimed CO or moisture removal Filters need regular care How big should a range hood be?
For a wall hood, HVI's answer is about 100 cfm per linear foot of cooktop, which puts a 30-inch range near 250 cfm; island hoods get 150 cfm per foot. The HVI range hood brochure also lists 300 cfm for a 36-inch wall hood and 400 cfm for a 48-inch one, and says the hood should match the range's width and hang at the maker's height.
Stacks on this How much airflow does a range hood need?
Turn over for the detail
Size alone doesn't settle it; capture depends on coverage and habits as much as the fan. With no government rating standard, look for HVI-certified airflow and sound figures.
Why does a gas stove need a hood?
Because gas burners add combustion gases to the air you breathe, not just cooking smoke. EPA's nitrogen dioxide page says indoor NO2 often exceeds outdoor levels in homes with gas stoves, and NO2 can irritate the airways and raise the risk of respiratory infections in young children.
Carbon monoxide matters too. EPA's carbon monoxide page puts levels near a properly adjusted gas stove at 5 to 15 ppm, and 30 ppm or more near a poorly adjusted one. LBNL found hoods catch the most on the highest setting with pots on the back burners; on quiet settings, front-burner capture fell below 40%. CPSC wants a CO alarm on every level and outside sleeping areas.
Stacks on this How do you clear the air around a gas stove?
When does a hood need makeup air?
Under the current IRC (section M1503.6), a hood able to exhaust more than 400 cfm needs makeup air when the home has a gas, oil or wood appliance that isn't sealed-combustion or power-vented. Many towns require it no matter what, so check locally. The code's makeup-air damper must be gravity-operated or motorized and open on its own whenever the hood runs.
Stacks on this When does a range hood need makeup air?
Turn over for the detail
The reason is pressure. A strong hood in a tight house can pull air back down a water heater or furnace flue, bringing combustion gases with it. Ask a qualified pro for a worst-case depressurization (combustion safety) test before adding a big hood. If you're unsure, call a licensed pro.
Source the documents listed on this stack's sources card
Next Ducted or recirculating?↓Ducted or recirculating?
Ducted, whenever the kitchen allows it, because only a ducted hood sends moisture and gases outdoors. The IRC permits listed ductless hoods if installed per the instructions with other ventilation in place, but an LBNL review knows of no residential product that claims to remove CO or water vapor.
A ducted hood's duct must be galvanized steel, stainless steel or copper, and it must end outdoors, never in an attic or crawl space. Over-the-range microwave hoods are a middle ground: an LBNL study of microwave hoods measured 40% to 85% capture from front burners and 60% to 100% from back ones.
Stacks on this Ducted or recirculating: which hood should you get?
Video from the Broan-NuTone channel on YouTube: How to Use a Range Hood Properly | Kitchen Ventilation Tips for Better Airflow. That channel has no tie to Air in the House; nothing loads from YouTube except the still picture until you press play. Kitchen numbers
Chart drawn by Air in the House from figures cited in this stack.
Quick cards
Short questions people ask next, one answer each.
Does an induction or electric cooktop still need a hood?
Yes. Cooking itself makes particles, grease and steam whatever the heat source, and LBNL measured single cooking events driving PM2.5 above 300 µg/m³. The 100 cfm code minimum applies to every kitchen.
Can the range hood share a duct with the bathroom fan?
No. The IRC wants the hood on its own duct, apart from every other exhaust system, airtight and with a backdraft damper.
Can a range hood exhaust into the attic?
No. The IRC bars kitchen exhaust from discharging into an attic, crawl space or other indoor area; it must reach outdoors.
Can PVC pipe be used for a range hood duct?
Generally not. The IRC calls for galvanized steel, stainless steel or copper, with PVC allowed only under a concrete slab for downdraft units installed as the code describes.
Is there an official rating for range hood performance?
No government standard exists, HVI says. Look for HVI-certified airflow and sound ratings instead of a maker's own claims.
Does a clothes dryer need makeup air too?
Sometimes. The IRC requires makeup air for dryer installations exhausting more than 200 cfm, a separate rule from the 400 cfm hood rule.
Where these cards come from
Sources: HVI's range hood brochure, the 2024 IRC exhaust chapter, ASHRAE 62.2 as summarized by DOE, three LBNL studies, and EPA's NO2 and CO pages, plus CPSC, read October 2026. Left out: brand and model picks, the unsourced "100 BTU" sizing rule, and installation prices.
- Berkeley Lab individual cooking events can push short-term PM2.5 above 300 µg/m³
- International Residential Code 2024 IRC exhaust chapter
- Home Ventilating Institute HVI range hood brochure
- EPA nitrogen dioxide page
- EPA carbon monoxide page
- Berkeley Lab LBNL study of microwave hoods
Cards are written by the Air in the House editors from the documents above and dated when they were last checked. How stacks are made