When rosin-based or rosin-containing fl uxes are heated,
a substance called colophony is produced, which is one
of the major causes of occupational asthma. In order
to reduce exposure to colophony, rosin-based fl uxes
have been exchanged for no-clean or synthetic fl uxes
that contain no rosin or very low percentages. While
this reduces or eliminates exposure to colophony, new
chemical irritants may be introduced into the work place,
many of which pose a more substantial threat to workers.
Over 95% of the total fume produced from rosin-based
fl uxes are in the form of particulates. Chemical exposure
from fl ux fume varies widely and is dependent on the
chemical composition of the fl ux. Non-rosin or low-rosin
fl uxes use chemically aggressive substances such as
acids, solvents, or alcohols in place of rosin to improve
the cleaning action of the fl ux. This is also true for
Lead Free solders.