Quoted:
I understand that the definition of "Destructive Device" includes poison gas.  However, in attempting research, I have been unable to locate any evidence than anyone has actually tried to register poison gas with the ATF.  If this has been done/attempted before, I am interested in hearing what was required.  Particularly, what did the ATF require with respect to serial numbering the gas?

(f) Destructive device
The term “destructive device” means
(1) any explosive, incendiary, or poison gas

 (A) bomb,
 (B) grenade,
 (C) rocket having a propellent charge of more than four ounces,
 (D) missile having an explosive or incendiary charge of more than one-quarter ounce,
 (E) mine, or
 (F) similar device;

(2) any type of weapon by whatever name known which will, or which may be readily converted to, expel a projectile by the action of an explosive or other propellant, the barrel or barrels of which have a bore of more than one-half inch in diameter, except a shotgun or shotgun shell which the Secretary finds is generally recognized as particularly suitable for sporting purposes; and

(3) any combination of parts either designed or intended for use in converting any device into a destructive device as defined in subparagraphs (1) and (2) and from which a destructive device may be readily assembled. The term “destructive device” shall not include any device which is neither designed nor redesigned for use as a weapon; any device, although originally designed for use as a weapon, which is redesigned for use as a signaling, pyrotechnic, line throwing, safety, or similar device; surplus ordnance sold, loaned, or given by the Secretary of the Army pursuant to the provisions of section 4684 (2), 4685, or 4686 of title 10 of the United States Code; or any other device which the Secretary finds is not likely to be used as a weapon, or is an antique or is a rifle which the owner intends to use solely for sporting purposes.

Quoted:
What about those "bombs", which you get from a Veterinarian, to kill fleas?

You have to leave the house, once you trigger one, so do we now need permission from BATFE to kill fucking fleas?

Quoted:
Poison gas is against the Geneva convention.
I'm no expert, but I would think you would be rejected from ATF approval