Has any one seen this show called Cool Stuff: how it works?

Because I saw this episode were they showed this special filming technique that uses mirrors to make and light to make air visible. it was really cool and I forgot what the camera or the technique was called. So this is my real question. Does anyone know what the camera is called or at least what I am talking about?Has any one seen this show called Cool Stuff: how it works?
Sounds like Schlieren optics:





http://en.wikipedia.org/wiki/Schlieren_p鈥?/a>