Acrolein forms above 280 celsius, which is well beyond what the average vaporizer will be set for (from under 200 to around 260).

More than that, you'll know immediately it's happened because it tastes awful.

Same thing with formaldehyde - nobody is ever going to willingly inhale it, since its presence means your vape is going to taste awful.

http://dailycaller.com/2016/03/05/formaldehyde-fears-used-to...