AC Infinity CLOUDLINE S4, Quiet 4” Inline Duct Fan with Speed Controller

The CLOUDLINE S4 is an inline fan that sits inside a 4-inch duct run. The listing rates it at 205 CFM and 28 dBA. It comes with a wired 10-speed controller and also works with AC Infinity's UIS smart controllers. It has a PWM-controlled EC motor, dual ball bearings and a mixed-flow design that AC Infinity says keeps air moving through ducts with high resistance. The body is 6.9 x 11.9 x 7.4 inches.

What it's built for

AC Infinity lists four uses: ventilating grow tents, moving heated or cooled air between rooms, circulating air, and cooling AV racks. "Exhaust odors" is in there too. It isn't sold as a kitchen product.

Can it help with cooking smells?

Indirectly. It can pull stale air out of a closed pantry, a utility room or a closet near the kitchen through a duct to the outside. You can also use it to push air from one room to another, which helps when one room always ends up stuffy.

Be careful about one use people search for: putting it inside a range hood duct to boost a weak hood. The listing says nothing about grease-laden air or kitchen exhaust. Before you add any fan to a hood's duct, check the hood manufacturer's instructions and your local code. Most hood problems have simpler causes anyway, like a blocked duct, a stuck damper or a saturated filter. Our range hood troubleshooting guide covers those.

Who it's for

DIYers comfortable running 4-inch ducting who want quiet, adjustable airflow for a small space. The 10 speeds let you run it low most of the time and turn it up when needed.

Who should skip it

If you want something that looks finished on a ceiling, this isn't it. There's no grille or housing for a room. If you can't run a duct to the outside or into another room, it has nowhere to send the air. And if the smell problem is upstairs bedrooms after dinner, start with containment. See stopping cooking smells going upstairs.

How it compares

• Panasonic WhisperCeiling FV-0511VQ1: a ceiling exhaust fan with a grille, 50 to 110 CFM and under 0.3 sone. It costs about twice as much (around $168 vs $90) but is designed to be installed in a living space.
• Everlasting Comfort draft stopper: if the issue is smell leaking out of a closed kitchen, sealing the gap under the door costs a fraction of any fan.

It has 4.7 stars from about 4,250 Amazon reviews. For the order to tackle things in, see the main cooking smells guide.