Clean Air vs. Dirty Air

During my first year as a NASCAR fan, there were a couple of phrases that I heard over and over again: clean air and dirty air.

Honestly, I had no idea what this meant.

Here's what I knew: clean air = good; dirty air = bad.

... but what do these phrases really mean?

Simply put, a driver does not have clean air if there is a car in front of them. Being at the front of the pack is ideal, not only because that means a driver is in p1, but also because it allows the driver to avoid dirty air.

Sam Hornish, Jr., now a part-time driver in the NASCAR Nationwide Series for Joe Gibbs Racing, describes dirty air like being on a highway: if you ever "got too close to a semi-truck and felt that turbulence--that is kind of what it's like."

It's important to note that dirty air affects the cars differently on the various tracks because each track allows for different speeds, and speed is a huge factor.

"The faster you are going, the more it affects the car," said Hornish. "If someone is in front of you at Talladega, it is very different than being behind someone at Bristol."

The reason clean air is crucial for a car's speed is because of how dependent the cars are on aero, which affects the car's down force.

When another car is too close in front of a driver, the driver loses down force.

Hornish explains that this causes an aero push; "meaning, you can turn the wheel, but the car does not want to turn."

So, yes... clean air = good, dirty air = bad. But now we know why.