Sleeping gas was stored in easily breakable flasks that would put most guards to sleep as soon as they smelled it. Transporting the gas could be a risky venture for careless thieves if the flask broke while in their possession.
The cost of sleeping gas depended on the size. A flask of sleeping gas suitable to knock-out a smaller guard cost 5 gold. A flask for a regular sized guard cost 10 gold. Any kind of guard over 7 ft. (2.1 m)tall required a large flask costing 20 gold.