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Appendix C Sensor Cross-Sensitivity Chart
The table below provides the cross-sensitivity response of the PhD Lite toxic gas sensors to common interference gases. The values are expressed as a percentage
of the primary sensitivity, or the reading of the sensor when exposed to 100ppm of the interfering gas at 20ºC. These values are approximate. The actual values
depend on the age and condition of the sensor. Sensors should always be calibrated to the primary gas type. Cross-sensitive gases should not be used as sensor
calibration surrogates without the express written consent of Biosystems.
SENSOR
CO H
2
S SO
2
NO NO
2
Cl
2
ClO
2
H
2
HCN HCl NH
3
C
2
H
4
C
2
H
2
Carbon Monoxide(CO)
100 10 5 10 -15 -5 -15 50 15 3 0 75 250
Carbon Monoxide (CO+)
100 350 50 30 -60 -60 -120 50 n/d n/d 0 75 250
Carbon Monoxide (CO-H)
100 10 5 n/d (-) (-) (-) 5 n/d n/d n/d (+) (+)
Hydrogen Sulfide (H
2
S)
0.5 100 20 2 -20 -20 -60 0.2 0 0 0 n/d n/d
Sulfur Dioxide (SO
2
)
1 1 100 1 -100 -50 -150 0.2 n/d n/d 0 (+) (+)
Nitrogen Dioxide (NO
2
)
-5 -8 -1 0 100 90 270 0 n/d n/d 0 n/d n/d
Chlorine (Cl
2
) (nonspecific)
0 -3 -1 0 110 100 310 0 n/d n/d 0 n/d n/d
Chlorine (Cl
2
) (specific)
0 -3 0 n/d 12 100 0 0 0 2 n/d 0 0
Chlorine Dioxide (ClO
2
) (nonspecific)
0 -1 -0.3 0 40 33 100 0 n/d n/d 0 n/d n/d
Chlorine Dioxide (ClO
2
) (specific)
0 0 0 n/d n/d 0 100 0 0 0 n/d 0 0
Ammonia (NH
3
) –21
0 <5 0 n/d 0 0 n/d 0 0 0 100 0 0
Ammonia (NH
3
) -04
0 130 70 15 -5 -50 -150 0 5 0 100 0 n/d
Phosphine (PH
3
)
0.5 25 20 n/d (-) (-) (-) 0.1 n/d n/d n/d 1 0.5
Hydrogen Cyanide (HCN)*
0.5 350 160 -5 -100 -20 -60 0.1 100 65 -5 50 n/d
n/d = no data, (+) undetermined positive, (-) undetermined negative
O
2
Sensor/CO
2
Cross Sensitivity: The output of the O
2
sensor used in the PhD Lite will be enhanced by approximately 0.3% of signal per 1% of CO
2
.
*Reduced sulfur gases (H
2
S and SO
2
) are considered to be HCN sensor poisons. HCN sensors are not recommended for use in areas prone to sulfur gas presence.
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