I looked into buying one of these cameras around 18 months ago. There is a huge price range and from what I could see an equally big difference in quality, so I suspect that the results depend very much on the camera in use and also the skill and experience of the operator.
There are training courses for their proper use which lead to industry qualifications.
I believe that if you are going to use this process for leak detection then an ISO qualified firm with a good level of PI insurance would be the way to go, because if you engage a leak detection company for their specialist services and they miss an issue that causes you a financial loss as a consequence then it would be relatively easy for a dispute or mediation process to lay a significant part of the responsibility for your loss back onto the company that missed the leak.
They might ask you to sign disclaimers or liability waivers etc. but I believe that under the Commerce Act or Fair Trading Act or similar legislation nobody can contract out of responsibility for the service that they provide commercially (unless you are specifically instructing them to do something that is outside their acknowledged field of expertise).
