I'v got into a habit of taking my truss tube outside well before I will use it. Instead of taking everything outside, I just rest the truss tube horizontally on an old vinyl 3 seat couch in the back porch. This couch is lined up east/west, not a problem at all till a couple of days ago. The setting sun shone through the trusses side onto the mirror and started melting a small hole in the arm rest of the couch.
Luckily I was near by and smelt the result.
Should have known better.