Distilled / Sterile water should be used in humidifier and should be changed daily. Water shouldn’t be left in it when not in use.It should also be cleaned to avoid any mould growth.

Why not boiled tap water

Boiling will kill microbes but still have minerals and other contaminants.

It is hence not desirable to use it.

Which other contaminants and what minirals effect on that ? @Amrjit

sterile water or tap water

untill unless we can use tap boiled water also

Absolutely right give any references@arvind