Would this be considered HIIT?

by Mike
(Lansdale PA)

I run stairs a few times a week and lift weights twice. I keep my lifting to compound joint exercises in a circuit fashion starting with moderate weights going to heavy, all with dumbbells. But my question is regarding my stairs routines.

I typically run 3 times a week, occasionally 4 and I mix it up. By mix it up, I don’t do the same routine twice a week. An example would be on Monday I would warm up by walking a “flight” (a flight is equal to 4 floors/80 steps) up and down, then I will run up and down for two “flights”, taking each step (all 80), and on the next “flight” I will sprint up, taking two steps at a time (takes ~ 20 seconds from bottom to top), then I repeat the 2 running flights, followed by a sprint (no rest in-between flights). I do this 6 times, than walk a full flight up and down to cool down. Takes about 25 minutes to do the 20 “flights”. On Thursday I will walk a “flight”, than run 4 “flights” followed by 2 sets of sprints, where I take them 2 steps at a time, jog down and sprint again. I do this 3 times. Same number of “flights”, 20, but the back to back sprints really seem to change things up, it feels very different. On Friday I typically run several “flights” (about 12 minutes or so) than will do 4 to 5 sets of sprints in the middle, walk a “flight”, than run for the remaining 10 minutes. My question is, are any of these routines considered HIIT?