Farouk Shami founded Farouk Systems in Houston in 1986, according to the company. He was a hairdresser who, in the company's telling, became ill and learned he was allergic to the ammonia in hair color, so he made his own. A decade later came the idea CHI is known for. The company says that on a 1997 trip to Italy, Shami saw how a pizza crust stayed moist when baked with ceramic heat, and it went on to launch what it calls the very first ceramic hairstyling iron, the original CHI.

That is why CHI heat protectant shows up next to so many flat irons. Heat is the problem the brand was built around. A dermatology study summarized by Newswise noted that temperatures of 347 to 419 degrees Fahrenheit for as little as five minutes are enough to damage most hair, and the American Academy of Dermatology suggests flat irons on dry hair, on a low or medium setting, no more often than every other day.

A protectant does not make heat harmless. What it can do is coat the strand, cut friction and help you get a smooth result in fewer passes, which is the real win.

The first grid is CHI, from the 44 Iron Guard spray to leave-ins, a gel and a finishing spray. The second grid is eight heat protectants I would compare them with. My tip: spray section by section on dry hair, comb it through, and wait until it feels dry before the iron touches it.

CHI 44 Iron Guard Thermal Protection Spray is the most reviewed CHI product here and the one most people mean by CHI heat protectant. The brand says it forms a protective barrier, and its formula lists hydrolyzed silk and keratin. Royal Guard Heat Protecting Spray is the one with a stated number, heat protection up to 450 degrees Fahrenheit, and it lightly conditions as it goes.

CHI Silk Infusion is the cult bottle, an alcohol-free silk leave-in with a 4.7 rating. It is less a heat spray than a smoothing finish, so a few drops on the ends after styling is enough. Keratin Mist and the Keratin Leave-in Conditioner are lighter conditioning sprays whose labels both mention heat protection, good on towel-dried hair before a blow dry.

Straight Guard Smoothing Styling Cream is for round brush blowouts on curly or wavy hair, since it helps relax the curl and block humidity. Infra Gel is a maximum control gel, and Keratin Flex Finish Hair Spray is a flexible hold spray with argan and jojoba oils to finish. Several of these have only a handful of reviews, so start with the two sprays.

What I would skip: Silk Infusion as your only protection before a flat iron. It smooths beautifully, but pair it with 44 Iron Guard or Royal Guard when the iron is hot.

Bumble and bumble Hairdresser's Invisible Oil Heat Protectant is the most reviewed product in this edit, a leave-in spray that primes and cuts frizz. It is the one for dry, thick hair that drinks product. Moroccanoil Perfect Defense is the opposite, a weightless dry spray that will not flatten fine hair.

COLOR WOW Dream Coat is the anti-humidity pick. It works on damp hair before a full blow dry, and people with frizz tend to swear by it, though its rating is lower than the rest here. Olaplex No. 9 is a serum with antioxidants against heat and pollution, and K18 HeatBounce is a leave-in with heat protection up to 450 degrees.

Living Proof Perfect Hair Day Heat Styling Spray also lists 450 degrees and works on damp or dry hair. Oribe Gold Lust Dry Heat Protection Spray is a dry conditioning mist with a glossy finish, and Drybar Hot Toddy is a light mist with a satin finish.

If you flat iron often, pick a formula with a stated temperature and keep your iron at or below it. If you mostly blow dry, a leave-in style protectant does more for you, because it also helps with frizz and tangles.

What I would skip: stacking two heavy leave-ins. On fine hair, the Bumble and bumble oil and K18 together will leave the lengths limp.

I think CHI heat protectant earns its place because the brand has thought about heat for longer than most. Start with 44 Iron Guard if you flat iron, add Silk Infusion for the ends, and use Straight Guard if you blow dry curls straight. If you want a clear temperature on the label, Royal Guard, K18 and Living Proof all say 450 degrees. Whatever you choose, lower the iron's setting before you change products, and give each section one slow pass instead of three fast ones.