When we did our launch, we originally planned on a Hydrogen launch because we were informed of the Helium shortage. We bought all of our equipment based on Hydrogen being the gas. This is important for those that do not know as Hydrogen equipment has specific fittings so that it will not work with any other gas equipment. This is to prevent accidental/unexpected use of Hydrogen due to it being so volatile.
When we showed up to pick up the tank of Hydrogen, the employee really hesitated selling us the tank of gas. He explained that the flames from Hydrogen gas is colorless, so we could be on fire before we even saw the flames. The flames only display color when the flames catch other material begins to burn. He ultimately exchanged all of our Hydrogen equipment for Helium, and sold us the tank of Helium.