I used to smoke synthetics , JWH etc some time ago with my friends. Mainly cause it has a trippier effect than cannabis. Doesn't last long though, maybe half an hour. Usually smoked it with gravity hits. You can smoke to much however, not good for people sensitive to paranoia.
Dude, spice is so bad for your health. Its not worth it even if you are worried about being tested. Id quit smoking for a while before i touch spice again. but, it DOES get you high.