GN3 isn't the whole answer though - in order to carry out a PIR you have to be experienced in doing so. If you are experienced in domestic and have 2391, you can't simply go and test an oil tanker depot and vice versa. You need to spend some time with someone who has the experience in order to be able to stand up before the judge and state that you are qualified and experienced.
Experience helps you to know what common defects to look for, what joe public / bobski the builderski might have been getting up to, what looks like they might form part of the original installation or be additionals and so on.
Experience helps you to know what common defects to look for, what joe public / bobski the builderski might have been getting up to, what looks like they might form part of the original installation or be additionals and so on.