As long as it is surface mounted or recessed (cord and other dangling fixtures are barred) and rated for wet locations, it is OK when installed consistent with the manufacturer's instructions (most require GFCI protection).

You can get wet rated recessed lighting (more specifically a wet rated trim kit) and use that.

Ronnatalie:

Thank you for your reply...no room for recessed lighting...a box will be tight.

Typing that made me wonder if there is code concerning how close an electrical box can be to warm/cold air ducts in a bulkhead...there is always one more thing I do not know...do not know enough to even think about it before it "crops up." I am in awe of trades-people!

Electrical boxes don't typically have any clearance issues with other systems. You might want to avoid allowing two dissimilar metal things from touching one another (especially pipes) for corrosion issues.

IC-style recessed fixtures also have no clearance issues. They can be installed touching framing members or other materials.

How about recessed or surface wall lights instead?

ronnattalie: thank you for the information; we opened the ceiling more and found the open area between ducts actually gets a little larger than the first spot we opened. I think a trip to HomeDepot is in order to buy 4 inch and 5 inch LED recessed housings and just try it before we call the electrician back to see the space.

btharmy: Thank you for the suggestion; I found a few that would work on the wall too....DH is not "loving" them; he prefers ceiling...he may not have a choice.