Table 11–
Specification of helium meters used for measuring functional residual capacity
Item
Specification
Linearity
0–10% helium
Accuracy
±l% of initial deflection
Resolution
<0.05% He
Gas flow
constant >200 mL·min
−1
, gas to be free of CO
2
and H
2
O
Response time
95% response time <15 s (meter + spirometer)