What are the fire code rules and general fire safety concerns when using rigid foam panels in the following applications:

- Exterior of wall with furring strips on top to form a vented rain screen behind siding.

- Exterior of roof with furring strips on top to form a vented roof plain

- Interior of roof to form an air tight vent baffle (a less traditional approach, but a possible retrofit)

- Applied to interior of ceiling and covered with drywall - the 'top side' would be exposed in the attic and covered with batts or blown insulation. (I know that this is not the typical use since you can usually handle all of your insulation needs in the attic by piling insulation on top of the ceiling joists. But I'm really just concerned with the 'what if' fire code concerns here.)

In each of these scenarios the foam is technically exposed in that it is not sealed between fire rated sheathing. Do the codes pose any restrictions on these uses? And above and beyond the codes are there any real world safety concerns with these applications? I've seen some of these approaches recommended from an energy efficiency standpoint, but I haven't heard much discussion about the fire concerns. Any input would be much appreciated.