(BBC) – Formula 1’s governing body has declared this weekend’s Singapore Grand Prix a ‘heat hazard’ race.

The FIA’s ruling, triggered because temperatures are predicted to exceed 31C amid high humidity in the tropical environment, means drivers could be using cooling vests during the race.

Using the vests is not mandatory, but teams must fit the system to their cars to ensure any drivers not using them does not gain an advantage by having a lighter car.

The Singapore Grand Prix marks the first time a race has been designated as a heat hazard under a new rule that was introduced this year.

However, it will not be the first time drivers have used the vests; teams have been testing them intermittently throughout the year.

Mercedes’ George Russell, a director of the Grand Prix Drivers’ Association (GPDA), tried it out in Bahrain earlier this year and said on Thursday: “Not everybody finds the top comfortable, but I think some find it more comfortable than others, and, of course, over time you’ll be able to adjust it to your own preferences.

“But the concept is good, and when you’re racing in 90% humidity, and the cockpits are getting on for 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, said that the FIA’s decision to declare a heat hazard was “fair”.

“Only hot is not too bad for us,” Sainz said. “We have that, for example, in Hungary, where it gets really hot, but it’s not humid.

“Humid on its own is not too bad at all if it’s not too hot. But when it’s 28C, 30C degrees plus humid, that’s when it gets to Singapore levels and it’s tough.”

Singapore has long been renowned as the toughest grand prix because of the combination of heat, humidity, the length of the race, which runs close to the maximum two-hour limit, and the bumpy track surface at Marina Bay.

Why was the heat hazard rule brought in?

The idea of a driver-cooling system was intimated after the 2023 Qatar Grand Prix, when heat and humidity left several drivers on the brink of collapse.

A number of drivers needed medical attention after the race. Frenchman Esteban Ocon vomited in his helmet, and Williams’ driver Logan Sargeant retired because he could not cope with the conditions any longer.

The drivers have had a mixed response to the vests, with some feeling they are uncomfortable and not especially effective.

Sainz said: “Teams are managing to make it work better and better every time we run it. At the beginning, we had it to work more or less for half an hour. Hopefully, now the whole system can work at least for an hour.

“It’s a two-hour race. I’ve done it 10 times in Singapore. If it breaks or it doesn’t work, I’m not worried. I’ll do the race and jump out fresh like I always do. But if it works, it’s better, because then you suffer a bit less.”

Sainz said he had used the system in the Saudi Arabian Grand Prix earlier this year, and it lasted about 15-20 minutes.

Aston Martin’s Fernando Alonso said: “The system works. The shirt itself, the material is a little bit thicker with all the systems on it so it is less comfortable. It is a trade-off; it is less comfy when you drive it, but it is a little bit cooler.”