Chief Fire Officers (and those immediately under them) are usually trained to degree level in all fire safety issues.
However when carrying out routine checks on high-rise buildings (rather than the rigorous ones which are now underway) they can't normally carry out destructive tests on things like insulation and cladding. They have to trust the assertions of the manufacturers and installers that the materials and methods used are up to the required specifications.
Those who are responsible for signing safety certificates frequently have to assume that others have done (or will do) their jobs properly. For example, I knew the guy (Bill Eastwood) who signed the safety certificate for Hillsborough Stadium before the terrible events there. As the report into the disaster showed, he was entitled to assume that Sheffield Wednesday and South Yorkshire Police would do their jobs properly by ensuring that the stand wouldn't become overcrowded.