What is a Q trap?

It is part of a mass spectrometer, nothing to do with plumbing. Since you posted in plumbing I am wondering if you could mean a P trap or a J trap, those are plumbing terms. http://en.wikipedia.org/wiki/Trap_(plumbing)

Hi Shaanwins

Q Traps are not used in the USA, but I understand that they can be used in a similar way to P Traps, S Traps, etc... all meant to keep sewer gasses out of the home/business.

As defined at one site, a Q Trap is used to "provide water seal & efficient functioning of the drainage system".

See image below... ;)

Mark