NaCl and KCl are contained in the flue gas of waste boiler.

Many papers, especially about numerical simulation or chemical reaction mechanism, regard these alkali chlorides as a gaseous species, even though the boiling point of NaCl and KCl is about 1700 K, which is much higher than typical temperature of flue gas of waste boiler.

Can I regard NaCl and KCl as a gas? or particle?

Thanks.