It’s amazing how much influence our hair can have over our emotions and sense of wellbeing. As Phoebe Wallace Bridge so rightly said in Fleabag, “Hair is everything. We wish it wasn’t so we could actually think about something else occasionally. But it is. It’s the difference between a good day and a bad day.”

Because I find this sentiment so relatable, I do just about everything in my power to stay on the “good” side of the hair day equation. I deep condition. I use scalp oil. I detangle my wet hair with a wide-toothed comb. However, no matter how often I’ve heard that cold air is imperative for setting a blow out, I’ve always skipped that step. I don’t know why, but I’ve never truly understood the importance of the “cool shot” button on the blow dryer.

That is until I got my hands on the new Dyson Supersonic Hair Dryer. Spoiler: it’s even lighter and faster than previous versions, making it a true treat for a hair-obsessed freak like me. Best of all, the cool air button is so visible and so ridiculously easy to use, that now I’m addicted. I barely even need to think about it—all it takes is a light touch to turn it on.

Once I became a “cool shot” convert, I discovered a whole new world. Yes, finishing my blow out with a jet of cold air from roots to ends really does make the style last longer—even my sweaty Zumba class can’t derail my straight, smooth hair—but the cold air also offers even more benefits than I realized.

The benefits of cold air on hair

After my divine encounter with the Supersonic cool shot button, I spoke with stylist Maria Roberts to understand why hair pros are so insistent on the use of cool air. The most immediate advantage? A blast of cold air keeps the cuticle from becoming overloaded with heat, thus protecting it from breaking and fraying.

Of course, one of the big advantages of a Dyson hair dryer is that it apparently never heats up the hair. However, Roberts says the extra cool air still helps seal the cuticle. “We’re talking about an optical effect, because by blowing the hair dryer with cold air in the right direction—i.e. downwards—the cuticle is set,” she says. This is why one of the biggest mistakes that can be made when trying to create waves or curls is to release them while they are still warm. The residual heat can undo the shape achieved and prevent the style from lasting; a cool shot “freezes” the style in place.

Cool air fights frizz

Finishing with a mini-dose of cold air not only fixes the hairstyle and adds shine, it’s also an excellent way to avoid frizz—especially if you have fine or delicate hair. In fact, Roberts tells me that at her salon in Ibiza—where the summer can be steamy—the cool shot is de rigueur for every one of the blow-outs the stylists perform. “We always finish with cold air at the roots to avoid frizz around the crown, something that’s very common in places with beaches and humidity,” she explains, adding that you can use also use the cool shot to avoid flyaway baby hairs on a polished updo.

How to use the cold air button on a blow dryer

Now that we’re all in agreement about how important it is to use the cool shot, let’s talk about how to correctly use it. Roberts recommends either dividing hair into sections or applying the air in a global way, focusing especially on the roots. From there, it’s quick: You only need to hit the hair for a few seconds with the cool air to achieve the life-changing, day-making results.