@WMH
As Arnie stated, the green gas canisters are quite safe when stored and handled in an appropriate manner. I work in a factory that, among other things, manufactures aerosol sprays. These sprays use a propane/butane mix as propellant. And the canisters we use are exactly the same as the ones used for green gas. In fact most sprays, from hair spray to shaving-foam sprays, use propane/butane as propellant. Just take one of the spray cans in your house and read the label. Besides the propellant used in the can you will also find precautions for storage and handling. The precautions are all