Singapore, Oct 3 : Formula 1's governing body has classified this weekend's Singapore Grand Prix as a "heat hazard" race for the first time, as soaring temperatures and high humidity threaten to push drivers to their physical limits.

The ruling by the FIA was triggered by forecasts of 31 degrees Celsius and oppressive humidity in the tropical city-state. Under the regulation, teams must equip their cars with driver-cooling vests, although using them is optional. The measure ensures that competitors who decline to wear the vests do not gain a performance edge from a lighter car.

It is the first time the FIA has invoked the new heat-hazard provision, introduced after the 2023 Qatar Grand Prix left several drivers requiring medical treatment. Esteban Ocon vomited in his helmet during that race, and Williams' Logan Sargeant was forced to retire after succumbing to the conditions.

Mercedes driver George Russell, a director of the Grand Prix Drivers' Association (GPDA), said he welcomed the concept after testing the vest earlier this year.

"Not everybody finds the top comfortable, but some find it more comfortable than others," Russell said.

"When you're racing in 90 per cent humidity and the cockpit gets close to 60C, it's a bit of a sauna inside the car, so I think we all welcome it."

Williams driver Carlos Sainz, also a GPDA director, called the FIA's ruling "fair."

"Only hot is not too bad for us. Humid on its own is not too bad. But when it's 28, 30 degrees plus humidity, that's when it gets to Singapore levels and it's tough," Sainz said.

Singapore has long had a reputation as the most demanding race on the calendar. The event runs close to Formula 1's two-hour limit and features a bumpy street layout under floodlights in stifling conditions.

The cooling system consists of a fireproof vest fitted with tubes through which chilled liquid is pumped. Cockpit temperatures can exceed 40 degrees Celsius, and drivers wear multiple fireproof layers in addition to helmets and gloves.

The FIA requires the system to last a full race distance, though teams admit reliability varies. Some designs fail after as little as 20 minutes, with the liquid warming up and making the driver hotter than without the vest.

Aston Martin's Fernando Alonso said the device was effective but came with drawbacks, Xinhua news agency reported.

"The shirt is a little bit thicker with the system on it, so it's less comfortable," Alonso said. "It's a trade-off - less comfy when you drive it, but a little bit cooler."

/IANS