Are there toxic concerns with using a heatgun/torch on plastic/acrylic? I am looking to bend a piece of plastic/acrylic (not really sure what I'm getting yet), for a craft project I am working on.

I watched this video https://www.youtube.com/watch?v=rkpqfcg1W_o

where they heat and bends a piece of acrylic, with a propane, or some other type of torch. To me, it seems like a really bad idea using a torch. He is also inside, which also seems like a really bad idea, unless he had a very good ventilation system...

I was thinking of using a hair-dryer, but I'm not sure if it would get hot enough, as well as doing this outside. 

I was curious if this seems like a bad idea? I would assume with proper ventilation I should be fine? I also do think that the torch overheated the acrylic in the video, which would not be a problem with a hair-dryer.
Yes, if you overheat it, most thermo-plastics will give off dangerous gases when heated above a certain temperature. For bending, you need somewhere between 100C - 170C (212&deg;F - 338&deg;F). Cast acrylic needs higher temperatures than extruded (due to the higher molecular weight), and thicker sheet need slightly higher temperature than thinner.

But do not go above 170C (338&deg;F) for extruded acrylic or 190C (374&deg;F) for casted. Just start off low and heat it slowly until the material will bend as you need it. It's only the bubbling and scorching caused by excessive heating that gives off the nasty fumes when burnt. 

From my post on Lifehacks &mdash; Working with acrilyc/plexiglass, electric strip heaters are generally recommended (depending on what you are trying to do), but any electric indirect infrared source can be improvised for occasional use. BBQ starters, heat guns, hair dryers, and even light bulbs have been used, but toaster ovens are a bit more problematic. 

Overall, low and slow is the key. You have to have a controllable heating source, so be careful.