from a Medical RRT

Due to the insulation of a drivers Helmet, heat is trapped around the head, circulating fresh cooler Air not only will extract that heat but it will provide breathing air 79% N2 - 21% O2 (oxygen) to your brain, boost energy, improve performance and reaction times.

Racing Oxygen levels
Until recently it was impossible to measure the amount of physical work and energy required during competitive racing. Researchers found that race car drivers use up as much as 13 times ( higher than resting heart rate levels) the amount of oxygen during a race, that's comparable to running a 8 -10 minute mile.

From a driver's point of view

This is a hot day and you and the crew have been working on the car in preparation for a run. You are sweating and drinking whatever fluids you can find. You push the car to the staging area where you wait 20-30 minutes to make your run. The sun is beating on you and the car. Asphalt and inside car temps reach 120-140 degrees so you put a towel over your head to keep cool. They tell you to get ready so you put on that nice thick 2 or 3 layer fire suit, boots, neck brace and helmet and you have a seat in the car. Nerves take over thinking about what you have to do driving and you start breathing hard. The harder you breathe the less and less air you have inside your helmet. Sweat starts rolling down your eyes and they start burning. You wait and you wait for another 5-6 minutes. You start the car up and bring it to the line to do your burnout with your visor up. Smoke, Dust and Fumes gets in your nose, throat and eyes. You stage the car, put your visor down when all of sudden the visor starts fogging up along with your glasses (if you are wearing any) so you can't see very well. Your pulse is up, you are sweating and breathing harder and still no air. Boom! You leave the starting line and make your run.

You stop on top end of the track and you can't get out of the car fast enough to catch your next breath and then you get back to the pits and do it all over again except you have a bad, bad headache.