Which of the following is true concerning the Stead-Wells spirometer?

a. Counterweights are necessary.
b. The pen and bell move in opposite direc-tions.
c. The pen recorder is attached directly to the bell.
d. On exhalation, the bell and pen move downward.

ANS: C
The pen recorder for the Stead-Wells spirometer is attached directly to the bell, so as the bell moves upward during exhalation, the pen also moves upward.