HUMIDITY CONTROL

							HUMIDITY CONTROL

Indoor air should have a humidity of between 40% and
60%. During the heating season water normally must
be added to the air to achieve this level. Humidifiers
operate on the basis of evaporating cool water from
wicks or meshes placed in the warm air ductwork, or
they inject steam directly into the air. Cold water
system can be sites for growth of moulds and
bacteria, so steam systems are preferred.        If the
heating system is based on a steam boiler, that boiler
is the likely source of the steam. Chemicals, usually
amines, are added to boiler water to prevent acid
corrosion of the boiler and pipes.         Morpholine,
cyclohexylamine, and diethylaminoethanol (TLVs are
20, 10, and 2 ppm, respectively) are commonly used.
Maximum air concentrations of the amines resulting
from this practice might be as high as 1 ppm, so there
is no problem from a toxicity standpoint. However,
the    odour     thresholds    for    morpholine    and
diethlaminoethanol are 0.01 to 0.1 ppm, and
objectionable odours may be detected by some
occupants.     A cure is to use a stem generator
dedicated to steam production for humidification
which does not utilize anticorrosive.