The Grove Racing driver revealed on the Fox Sports broadcast that his helmet air fan system malfunctioned during the immediate build-up to the Darwin finale.
He swiftly unplugged the system once he realised he was breathing carbon dioxide and went on to finish the race sixth.
However it was after the race that symptoms began to set in, Supercars medical delegate Dr Carl Le putting Allen on oxygen at the circuit.
Allen has since been undergoing further treatment in a hyperbaric chamber to prepare for the Townsville 500.
“On the Sunday [in Darwin] I had a little issue with the dry ice system,” Allen explained.
“The boys are investigating now, but something went a little bit wrong where I believe that a bit of carbon dioxide from the dry ice entered my helmet air.
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“I was a bit confused at first, because it smelt a bit different to what it normally does when it first turns on.
“And then within two seconds I was really struggling for breath, I was feeling like I was suffocating and really trying to work out what was going on.
“I don’t know why, just natural instinct, I pulled the helmet air off and that made it a bit better.
“When that happened it was quite frightening but once I got in the car and started racing I forgot about it, as you always do.
“Once the adrenaline wore off at the end of the race I became short of breath and really struggled.
“I asked a few of the guys around me and they took me off to good old Dr Carl and he was pretty concerned.
“Straight away once I told him he took me into the ambulance and pumped me full of full oxygen.
“The last few days I’ve been hyperbaric chambers filling my body with as much oxygen as I can just to make sure there are no health concerns moving forward.”
The last high-profile case of dry ice fumes affecting a driver was the 2019 Bathurst 1000, when Brodie Kostecki was forced to pull over on the warm-up lap on his Great Race debut when his helmet filled with carbon dioxide.
Driver welfare was a big talking point over this year’s Darwin weekend with both Kostecki and Thomas Randle missing Sunday’s race due to health complaints.
The Randle case was specifically related to driver cooling, the Tickford driver left with heat exhaustion after his cool suit failed on the warm-up lap of Saturday’s race.
Revised driver cooling rules introduced ahead of Darwin require drivers to have an operating cool suit and helmet fan if the forecast exceeds 32.9 degrees celsius.
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