This is how to take off the ESI probe (general purpose) and replace it with the APCI probe (good for hydrophobic things, triterpenes etc.), and also how to take off the APCI probe if someone else has left it on, and you want to get back to ESI. Next time, someone with more talent can do the voice-over.
Comment: You don't actually have to turn the QE off. Putting it in stand-by mode is also safe, and means the electronics stay warmed-up, so your mass accuracy will be more stable