The only designated smoking areas, IIRC, are outside, so you'd have to leave security and re-enter. (In other words, don't count on a smoke in the midst of a 25-minute connection).

Also, if you are connecting from Alaska to Horizon (or vice versa) in PDX, you may have some distance to cover in that 25 minute layover, as it would involve a change of concourses.

Mike