Gas for the purpose of this ARP shall be defined as the gaseous produces) resulting from the decomposition, dissociation, or combustion of liquid or solid mono or bi-propellants. Where other gases such as heated N₂, H₂, H₂O (steam), etc., which may have similar physical and/or chemical properties as the defined "gas", are used to effect testing economies; they may be considered as being included in this ARP.