Hydrogen
Hydrogen is the lightest substance known to man, and is non toxic, although it does not support life. Hydrogen is usefull to the industry as it is reactive, it burns and it has a very low boiling point.

Hydrogen is the lightest substance known to man, and is non toxic, although it does not support life. Hydrogen is usefull to the industry as it is reactive, it burns and it has a very low boiling point.