Moisture
A crucial point to always bear in mind is that water can be a very good conductor of electricity. Any panel that is damp or wet should NOT be touched or opened by an inspector.
Before even thinking about touching, inspecting or removing a dead front cover, the inspector should look carefully for signs of water or moisture staining on the panel or on its surrounding wall.
As we saw with the service entrance, any failures of the mast or cable entryways may result in water getting into the panel.
If there is any evidence of water, the inspector should recommend that the panel be fully evaluated and repaired by an electrical contractor, so delving further into the panel is not only potentially dangerous, it's also unnecessary.
In the inspection image above (courtesy of Jeff Pope), water is dripping off the branch circuit conductors. This panel should probably not have been opened.
Rusting Enclosures
It goes without saying that any panel or enclosure showing rust has been exposed to a high level of moisture. It may well be that a previous leak has been repaired, but the inspector should be extremely cautious of inspecting the panel any further.
Remember: The inspector's primary goal is to maintain both his own safety and that of his clients.
Damaged Breakers
There are several issues related to circuit breakers:
Are they rated for the model of panel they are installed in?
Do they have their handle ties in place on double-pole breakers so that both sides of the circuit can be shut off at the same moment?
Are there any signs of arcing, burning or smoke damage that would indicate that the breaker is not tripping as intended?
We will look at these issues in more detail later.
Signs of Arcing
As part of the initial visual inspection of a panel, the inspector should look closely for any signs of arcing or burn marks on the panel. Again, these may be the result of previously repaired problems, but don't count on it. Also, take a second to listen to the panel because, in many cases, you may hear arcing.
Arcing or smoke damage on the outside of the panel is obviously indicative of a previously significant and dangerous condition. It is recommended that the inspector, at a minimum, ask the homeowner for details of the damage, and its repair, prior to opening the panel.
Remember, there are many issues that can lead to this kind of telltale marking, and many of those can lead to the panelboard being live, or short circuits being caused by removal of the dead front. Complements of InterNachi