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The Inhalation Control Knob,
located next to the venturi lever
on certain model second stages,
adjusts the effort required to
initiate the inhalation cycle. As it is
turned in (clockwise), the opening
effort will increase. This will make
the second stage less sensitive
to sudden changes in ambient
pressure.
Turning the knob “out” (counter-
clockwise) will decrease the
opening effort to make breathing
easier. Sometimes a slight hissing
may be heard in this setting. If this
occurs, turn the knob clockwise
just enough to stop the hissing.
Inhalation Control Knob
