What a Range Hood Does and How It Works

A range hood pulls smoke, steam, and cooking odors up and away from your stovetop by using a fan motor to create suction. The hood has a wide metal or glass canopy that sits above your stove and funnels air into a duct or filter system. When you turn on the fan, it draws air upward through the canopy, traps grease and particles, and either sends the air outside through a wall or roof duct (called ducted or vented hoods) or filters it and recirculates it back into your kitchen (ductless or recirculating hoods). The strength of the suction depends on the fan's power, measured in cubic feet per minute (CFM)—the higher the CFM, the more air the hood moves.

Most home range hoods use one of two basic designs. A ducted hood is more powerful and removes odors completely from your kitchen because it sends air outside. A ductless hood is easier to install because it does not require ductwork, but it relies on filters to clean the air before sending it back into the room, so some smell may linger. Both types have a grease trap or filter that catches cooking particles before they reach the fan or ductwork.

Key Takeaways

  • A range hood uses a fan to pull smoke and steam upward through a canopy, then either sends it outside through a duct or filters and recirculates it back into your kitchen.
  • Ducted hoods remove odors completely but require ductwork installation, while ductless hoods are simpler to install but rely on replaceable filters to clean the air.
  • Grease filters or traps catch cooking particles before they reach the fan, and they need regular cleaning or replacement to keep the hood working well.
  • The fan's power is measured in CFM (cubic feet per minute)—higher CFM means stronger suction and better removal of smoke and steam.
  • Most range hoods have multiple speed settings so you can adjust suction strength depending on how much cooking smoke your meal produces.

The Canopy and Suction System

The wide metal or glass panel above your stove is called the canopy or hood, and its job is to catch rising smoke and steam. The canopy is shaped to funnel air toward an opening at the back or center, where it enters the ductwork or filter chamber. The larger and wider the canopy, the more cooking smoke it can capture before the smoke escapes into your kitchen. Most canopies sit 24 to 30 inches above the stovetop—the closer it is, the better it captures smoke, but it also needs to be high enough that you can cook without bumping your head or reaching into the heat.

Inside the hood, a fan motor spins a metal fan blade (or blower wheel) that creates the suction. When you turn the hood on, the fan pulls air from the canopy opening and pushes it either out through the duct or into the filter chamber. Most hoods have a switch with multiple speeds—low, medium, and high—so you can run the fan faster when you are searing meat or boiling pasta (which creates more steam) and slower when you are just reheating leftovers. Running the fan at the right speed saves energy and keeps noise down.

Grease Filters and How They Trap Particles

Before air leaves the hood, it passes through a grease filter or grease trap that catches cooking particles and oil. Most home range hoods use one of two filter types: a mesh filter (usually aluminum) or a baffle filter (stacked metal plates). Both types work by forcing air to change direction as it flows through, so heavier particles like grease and food bits fall out and collect in the filter, while air continues through to the fan or ductwork.

Grease filters need regular cleaning because a clogged filter blocks airflow and makes the hood less effective. Most mesh filters can be removed and washed in hot soapy water or placed in the dishwasher—check your hood's manual to see if yours is dishwasher-safe. Baffle filters are usually hand-washed because they are heavier and more delicate. If you do not clean the filter every month or two (depending on how often you cook), grease builds up, the fan has to work harder, and you may notice the hood is not pulling smoke as well as it used to. Some hoods also have a charcoal filter behind the grease filter in ductless models; this filter removes odors and needs to be replaced every three to six months because it cannot be washed.

Ducted Hoods: Sending Air Outside

A ducted hood connects to a metal duct that runs through your wall, ceiling, or roof and opens to the outside. When the fan runs, it pushes air and particles through the duct and out of your home completely. This is the most effective way to remove cooking odors because the smell leaves your kitchen entirely instead of being filtered and recirculated. Ducted hoods are common in houses and apartments where ductwork can be installed, and they are usually more powerful than ductless models.

The duct itself needs to be smooth and as straight as possible so air flows easily. Elbows and bends in the duct slow down airflow and make the fan work harder. The duct opening on the outside of your home should have a damper (a flap that opens when the fan runs and closes when it is off) to prevent cold air or pests from entering through the duct when the hood is not in use. Over time, grease can build up inside the duct, especially if the duct is long or has many bends, so it is a good idea to have the duct cleaned every year or two if you cook frequently.

Ductless Hoods: Filtering and Recirculating Air

A ductless hood (also called a recirculating hood) does not connect to a duct. Instead, it filters the air and sends it back into your kitchen. After air passes through the grease filter, it flows through a charcoal filter that absorbs cooking odors, then the cleaned air exits through vents on the sides or front of the hood and back into the room. Ductless hoods are easier and cheaper to install because you do not need to cut holes in walls or ceilings or run ductwork, making them popular in rental apartments or kitchens where ducting is not possible.

The trade-off is that ductless hoods are less effective at removing odors because some smell remains even after filtering, and they do not remove moisture as well as ducted hoods. The charcoal filter is the key to odor removal, and it wears out over time—usually every three to six months depending on how much you cook. Once the charcoal is saturated, it stops absorbing odors, so you have to replace the entire filter (you cannot wash it like a grease filter). This means ductless hoods have an ongoing cost for replacement filters that ducted hoods do not have.

Fan Speed, Noise, and Energy Use

Most range hoods have a control panel with multiple speed settings. Low speed is quiet and uses less electricity, making it good for light cooking or just removing lingering smells. Medium speed is the everyday setting for normal cooking like frying or simmering. High speed creates strong suction and removes heavy smoke quickly, but it is louder and uses more energy. Some newer hoods have a sensor that automatically turns on the fan when it detects steam or smoke, then adjusts the speed as needed.

Running the hood at high speed all the time wastes energy and creates unnecessary noise. A good habit is to turn the hood on a few minutes before you start cooking (so it is ready to work) and run it on medium or high while you are actively cooking, then leave it on for a few minutes after you finish to clear out any remaining smoke. If your hood is very loud on high speed, it may mean the filter is clogged or the ductwork has a blockage—cleaning the filter or checking the duct often solves the problem.

Common Problems and Maintenance

The most common reason a range hood stops working well is a clogged grease filter. If you notice the hood is not pulling smoke as strongly as it used to, remove and clean the filter first. If the hood is still weak after cleaning, check that the duct opening on the outside of your home is not blocked by leaves, bird nests, or ice. In winter, ice can form around the damper and prevent it from opening fully, which reduces airflow.

Another issue is a noisy fan, which usually means the fan blade is hitting something inside the hood (often grease buildup) or the ductwork has a dent or loose section. If the hood makes a rattling sound, turn it off and check inside the canopy for loose parts or debris. If the fan does not turn on at all, check that the power switch is in the on position and that the hood is plugged in (if it is a plug-in model) or that the circuit breaker has not tripped. If none of these steps work, the fan motor may need replacement, which usually requires a technician.

Frequently Asked Questions

Do I need a ducted hood or a ductless hood?

Ducted hoods are more powerful and remove odors completely, so they are better if you cook frequently or like strong-flavored foods. Ductless hoods are easier to install and work well if you cook occasionally or cannot install ductwork. If you rent, check your lease—many landlords do not allow ductwork installation, so ductless is your only option.

How often should I clean the grease filter?

Clean the grease filter every month if you cook daily, or every two to three months if you cook a few times a week. A clogged filter makes the hood less effective and forces the fan to work harder. Most mesh filters can be washed in hot soapy water or the dishwasher, while baffle filters should be hand-washed.

What does CFM mean and how much do I need?

CFM stands for cubic feet per minute and measures how much air the hood moves. Most home kitchens need 100 to 400 CFM depending on the size of the stove and how much you cook. A general rule is 100 CFM per linear foot of cooktop width, so a 3-foot stove needs about 300 CFM. Check your hood's manual or the product label to see its CFM rating.

Can I use a ductless hood if I have a ducted duct already installed?

Yes, you can install a ductless hood even if ductwork exists, but you would not be using the duct. A ductless hood does not need any connection to the outside, so the old duct would just sit unused. Some people cap off the old duct opening to prevent drafts.

Why does my hood smell like grease even after I clean the filter?

If the filter is clean but the hood still smells, grease may have built up inside the ductwork or on the fan blade. In a ducted hood, have the duct cleaned by a professional. In a ductless hood, the charcoal filter may be saturated and need replacement. Also check that the damper on the outside duct opening is not stuck closed, which can trap odors inside.