How long will you wait?

I recently acquired a space heater that I thought would be good for my office. I turned it on and it fanned out cool air as I waited for it to warm up. It’s been 3 minutes now and my leg is cold because it’s right next to the “heater”. I probably won’t wait much longer before turning it off and getting rid of it. 

How long do you wait when it’s clear something isn’t working?