PEIt is quite clear to me why the plant blew up!
Good luck, but my advice is to be careful, be very very careful!
You are perhaps confusing the manufacturing of azide compounds (a dangerous process) with the use and storage of the finished compound.
Hardnener #3 required no registration/regulation with the U.S.Dept of Transportation and was relatively inflammable and safe to use. I don't know if the plant blew up making this chemical or another.