Farts
Acetylene could be considered dangerous, as it is highly inflammable
I'm pretty sure you need a completely different kind of engine for that, as well as pressurized storage tanks. I wouldn't get natural gas, that stuff is way more dangerous than gas.
chlorine gas
very dangerous
Predators, they are dangerous when you are a prey.
R 134 is freon gas. In small amounts, the exposure to freon gas is not dangerous. In larger amounts, freon can cause respiratory issues.
mustard gas tear gas poison gas
yes it is
its combustible
Yes, methane, a dangerous greenhouse gas.
Yes, it is dangerous to leave the pilot light out on a gas appliance as it can lead to a buildup of gas and potential fire or explosion hazards.
A fermi gas is a model from quantum mechanics first proposed by Fermi. A neutron star is said to be an example of a Fermi gas, and that would indeed be a dangerous place.