Tim spoke with Sachiko Koyama, an olfactory biologist at Indiana University and co-author of a comprehensive review of the ways essential oils’ impacts on the body are affected by the mode of delivery (by inhalation, topically, or by ingestion). Luckily, they can almost always be turned off.

The colors can be relaxing or a little cheesy, depending on your tastes. Lights: Most ultrasonic diffusers light up in some fashion or another, often in a rainbow of colors.Intermittent diffusing: It’s nice when there’s an option for the diffuser to mist or spray oil for a set amount of time and then rest, diffusing intermittently this pattern keeps the diffuser going longer on a single fill.(You should empty and wipe out your diffuser every few days if you’re not using up all the water.) It’s a nice feature but not necessary. This function allows you to run the diffuser several times without refilling the water. Timer: Many medium and large diffusers have a timer that will turn off the diffuser after one or a few hours.

This can be annoying to clean but it’s not a dealbreaker, especially if your diffuser is going to be more of a set piece on a mantel for occasional mood-setting than a product in constant use. Fancier diffusers made from materials other than plastic often have two layers of lids-one functional and one decorative.

Lids: The easiest to use (and clean) diffusers have just one lid.

Generally, better materials tend to appear on pricier, smaller models. Most people will opt for the common semitranslucent white plastic options, but you can find oil diffusers in other materials, like ceramic, porcelain, fake wood, or even real wood.

Material: This is a displayed object, so aesthetics matter.

We’ve observed that impacts how effective the diffuser will be overall and how interesting it will be to look at (a piddly stream of mist isn’t very exciting).

Power: Regardless of tank size, we wanted to see a strong stream of mist.

A larger tank tends to work a bit better for a larger space.

Generally, larger tanks mean thicker mist and longer runtimes without needing refills. Ultrasonic diffuser tank sizes range from 100 to 500 milliliters the best diffusers balance the benefits of a bigger size with a small footprint.

Tank size: The size of the tank, more than any other detail, determines how you’ll interact with the diffuser.

Modern american super-heavy tank