Good point, however my comments where maybe a poor attempt at light hearted banter (exam nerves ?) if you check my profile or the who/what/where thread i think that after 18 years of working on A/C although im no expert i know a bit. Also if the company approval system works and you work for a reputable company you should never get past the Quality Department interview prior to being given your approval stamp if you are not suitable to issue CRS etc. I think in all circumstances its down to the individual if your not sure about something read the book again, speak/Phone somebody else with more experience, phone the helpdesk,etc. IMHO even if a person has worked on the same A/C type for 15 years if they have never encountered a particular snag or job before but the 'new boy' has seen/done it a few times in his first few weeks on type who is the expert ?