Many are, but not all. (The divide seems to be somewhere along the lines of a fluffy understanding on whether the spell efect actually consist of producing flames or not.) Also, there are quite a few non-fire spells equally affected, including most, but not all, evocations. Your best bet to find out about particular spells is to check the manual. (It's one of the reasons I still have it sat on my desk after years of playing. And months of not playing for that matter.
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