Typical Gauge Sensitivities relative to Nitrogen

Gas Ion
Gauge
Pirani
Gauge
Thermocouple
Gauge
H2 0.6 1.3 1.3
D2 0.4 - -
He 0.25 1.0 1.0
CH4 1.4 1.64 1.64
NH3 0.65 - -
F 0.8 - -
Ne 0.29 0.9 0.9
CO 1.1 1.0 1.0
N2 1.0 1.0 1.0
C2H6 2.8 - -
O2 0.8 - -
Ar 1.4 0.66 -
CO2 1.45 1.1 1.1
SO2 2.1 1.0 -
CI2 1.3 - -
Kr 1.86 0.45 0.45
CF2CI2 2.9 - -
Xe 2.7 0.35 0.35
Br2 2.2 - -
Hg 2.7 0.34 0.34
Calor Gas 4.7 - -
C4H8 4.8 - -
C3H8 4.6 2.5 -
H2O 0.86 to 1.2 1.5 1.5
True Pressure = Indicated Pressure
Sensitivity Quoted Above

Properties of some Filament Materials

Property ThO2 W Re
CO production Unknown High High
CO2 production High Moderate Moderate
O2 consumption Low High High
H-C consumption Unknown High Low
Water entrapment High Low Low
Volatility in O2 Low High Very High
Good filament ¹ for .. Nitrogen Oxides
Oxygen
Sulphur Oxides
Hydrogen
Hydrogen Halides
Halogens
Halocarbons
Hydrogen
Hydrocarbons
Hydrogen Halides
Halocarbons
Halogens
(1) These are general recommendations and may not be true for all cases.