Yes, and it takes the pellets 15-20 minutes to evaporate under absolutely ideal conditions (high heat and air-flow). If you just dump them, more like 2+ hours.

It'd make a damned poor fumigant if it instantly activated when you were spreading it around the area.

If you were using it in this fashion, a ventilating machine would about be mandatory.

https://furtherglory.files.wordpress.com/2014/06/machine06.jpg

This machine at Dachau has some plausibility, but the whole "dumping pellets in the room" is just dumb. Of course, introducing it in gaseous form poses its own problems.