What Constitutes Ignition Protection?

I received a query yesterday from a reader asking about a really important issue related to marine electrical system component ratings for ignition protection. I say important because you don't want your boat to end up looking like the one shown here: Doug's question goes like this: Hi Ed,I would like to know if any classes of products accepted as inherently ignition protected, not in need of testing / a label. Specifically I am wondering about:- standard sealed inductive proximity sensors- ...