Cooling vests are a hot topic in the world of Formula 1.

Andrea Kimi Antonelli of Mercedes opened up about the “struggle” he faced during the sprint qualifying round ahead of the 2025 United States Grand Prix in Austin, Texas.

To combat the extreme temperatures, the 19-year-old driver turned to his liquid-cooled vest. The technology was developed in reaction to the 2023 Qatar Grand Prix, which was held in intense heat and humidity.

Fast forward to Austin, the Fédération Internationale de l’Automobile (FIA) declared the event to be a heat hazard when the thermostat hit 91°F at the start of sprint qualifying on Friday, Oct. 17.

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Antonelli, however, experienced a shock failure with his cooling vest that left him “warming up” rather than, well, cooling down. He attributed his performance, in part, to this obstacle.

“I struggled in the car because I had a few physical issues,” he said after the race when speaking with press, initially referring to the sole free practice session ahead of the sprint shootout as seen in a video shared by Formula1.

“But the car felt good to be honest, and I was confident in SQ2,” he continued of the second round of sprint qualifying. “I was wearing the cooling vest, and we had a failure, so instead of cooling, it was warming me up, so I had a big struggle in the session.”

Antonelli was knocked out of SQ2 by six thousandths of a second by Lewis Hamilton of Ferrari.

During the Grand Prix, Antonelli finished 13th for Mercedes after an early collision with Carlos Sainz of Williams Racing, which knocked him down in rank. Still, he set the fastest lap of the race for the third time this year.

Max Verstappen of Red Bull Racing placed first. He became the first driver to win seven Grand Prix in the United States. His wins include four in Austin, two in Miami and one in Las Vegas.

Cooling vests have been a controversial topic among F1 drivers since they were introduced earlier this year. F1’s race director, Rui Marques, applied the regulation for the first time at the Singapore GP after the FIA declared a “heat hazard.”

Per F1 rules, the minimum weight of the car is increased by five kilograms when a heat hazard is in effect to accommodate the hardware used to activate the liquid-cooled vest sported by the driver.

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Vests are optional for drivers as of now. However, they will need extra ballast (a tuning option that allows more weight to be added to a car) so that those wearing the vests aren’t at a weight disadvantage.

Race venue temperatures aside, F1 drivers experience heat alone inside of the speedy cars that average between 210 and 220 mph.

Cockpits can reach up to 140°F due to the proximity of the engine, among other factors. Breaks, meanwhile, brakes produce heat that can reach up to 1,832°F.

In Singapore 2023, Williams driver Logan Sargeant retired from the race due to the extreme conditions, while Lance Stroll collapsed by his car after the race, near blacking out in high-speed corners.

A driver can lose as much as three kilos of body weight through sweat during the two-hour race in Singapore, which is equivalent to losing three liters of fluid.

Outside of hydrating and cooling pads in the layered fireproof suits, there’s not much drivers can do to stay cool in the cockpit.