Super-clean audio - how do they do it?

I'm watching the A&E show Intervention right now and I can't get over how there's absolutely no background noise in their audio tracks (fans, A/C, vents, etc.). How do they do this?

It's a run-and-gun reality show, so there's no way they turn off every single vent, fridge and A/C wherever they film. Whenever I do my own audio for an interview, I work very hard to make it as clean as possible - but there's always some sort of distracting background noise. I always capture room tone and have tried using SoundSoap to take it out but inevitably the sound I want to keep still gets colored.

Same thing in movies. How the heck do they capture audio that friggin clean?

I'm extremely picky about audio and will do just about anything to learn. Is there a DVD course or a book anybody would recommend?

Thanks so much!

Dan