Not
if it is maintained properly. The purifier is always slightly cool and damp.
Minerals in the water (especially calcium) can be precipitated on the outside
surface of the purifier during the evaporative process. These salts can build
up and form a good host for dust and dirt in the atmosphere. Naturally mildew
can grow in such a situation. The water purifier should be treated as a normal
household appliance and wiped down every couple of days with a damp cloth. This
prevents mineral salts from building up.