>Thanks for the input.  So this is an actual requirement then?

You will need to check the proper spec, as there are things like tracking
distance across the laminate to consider. I have not got involved in the
design of items to these sort of specs, am just aware of some of the
requirements.

The tracking distance can be improved by putting a slot in the PCB for
example, so it is not possible to have a carbonised surface on the shortest
possible line between primary and secondary points. You will often see this
in power supplies built to be squashed into miniscule spaces, where the
tracks on the PCB would otherwise be too close.

I repeat, get the spec for the market/authority that you are looking to work
to. There is just too much to try and remember, and too many gotchas that
will fry your liability insurance.

You will probably need to talk to a testing lab as well, as has been said in
this list before.

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