Sepang, Malaysia (AFP) - Kevin Magnussen said he was unsure about the halo cockpit safety system being trialled after having to flee his burning Renault on Friday, saying five seconds is "too long" to escape.
Magnussen, who had completed just one lap in Friday's first practice for the Malaysian Grand Prix, was forced to leap to safety when flames enveloped his engine outside the Renault garage.
"Get Kev out," came the cry on team radio and Magnussen quickly released his safety belts and removed his steering wheel, ejecting in a flash as the fire took hold behind the cockpit.
With Renault suspecting a faulty valve leaking fuel as the cause of the fire, Magnussen revealed he had no idea that the car was in trouble as he cruised to the garage.
"I didn't know," Magnussen told reporters. "Everything worked well on the car on the in lap. I just felt the heat."
The halo is designed to protect drivers from flying debris and impacts, and was developed after Jules Bianchi died from head injuries following a crash in the Japanese Grand Prix two years ago.
It was tested in practice at Sepang by Sergio Perez on Friday. World champion Lewis Hamilton ran a trial in Singapore two weeks ago.
But there are fears it can restrict the ability to get out of the car quickly in an emergency, and drivers have been given a target of extracting themselves within five seconds.
"Personally I've never run the halo so I'm not the best person to ask," Magnussen told reporters after practice ended, but added he felt the target time should be shorter.
"In my opinion five seconds is too long. If the car is on fire you don't want to take five seconds."
Renault engineers managed to get the Danish driver back out for the afternoon session after frantic repairs, and he came in 19th fastest in second practice for Sunday's race.