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9. FACTORS AFFECTING RESPONSE
9.1 Toxic Gases:
The presence of some gases can affect the sensor reading of the toxic gas for
which you are measuring. The chart below shows how each sensor listed in the
left column will respond to 100 ppm of the interfering gases listed along the top
row.
9.2. Cross Sensitivity Chart:
Sensor
Interfering Gas
CO H
S
SO
NO
NO
CL
2
2
2
CO
100 <10
<5
<10 ≈-15
<-5
H
S
<0.5 100
≈20
<2
≈20
-20
2
SO
<1
<1
100
0
≈-100
-60
2
NO
0
≈10
0
100
<25
0
NO
0
0
<-0.5 0
100
90
2
CL
0
≈-3
<-l
0
120
100
2
HCN
<0.5 n/d
160
-10
-190
-50
NH
0
130
70
20
0
-50
3
COu* 100 ≈315 ≈50
≈30 ≈-55
≈-30 <40 40
* Unfiltered Carbon Monoxide Sensor
H
HCN C
H
NH
2
2
2
4
3
<40 <15
<50
0
<0.5 0
0
0
<0.5 <45
2
0
0
0
0
0
0
<1
0
0
0
0
0
0
0
100
0.5
0
n/d 30
0
100
90
0
10. GAS SPECIFIC DATA
Gas
Range
Reso-
Accur-
Drift** Alarm
lution
acy*
Carbon
0-999 ppm
1 ppm
±5%
Monoxide CO
Hydrogen Sulfide
0-500 ppm
1 ppm
±5%
H
S
2
Chlorine CL
2
0-20 ppm 0.1 ppm
±5%
Hydrogen
0-50 ppm 0.1 ppm
±5%
Cyanide HCN
Ammonia NH
3
0-50 ppm
1 ppm
±5%
Sulphur Dioxide
0-50 ppm 0.1 ppm
±5%
SO
2
Nitric Oxide NO
0- 100 pm 0.1ppm
±5%
Nitrogen Dioxide
NO
0-50 ppm 0.1 ppm
±5%
2
Gas
Range
Reso-
Accur-
lution
acy*
Oxygen
0-30%
0.1%
±5%
O
2
*
Sensor accuracy, listed by City Technology, as a percentage of the reading.
**
Long term output drift listed as percentage of signal loss per month.
For Ammonia, an exposure of <25ppm/month is assumed.
*** Factory default settings. Recommended for normal use.
Alarm
Alarm
High***
STEL**
TWA**
*
*
<2%
200 ppm
100 ppm
35 ppm
<2%
20 ppm
15 ppm
10 ppm
<2%
1 ppm
1 ppm
0.5 ppm
<2%
10 ppm
4.7 ppm
4.7 ppm
<10%
50 ppm
35 ppm
25 ppm
<2%
10 ppm
5 ppm
2 ppm
<2%
50 ppm
25 ppm
25 ppm
<2%
8 ppm
5 ppm
2 ppm
Drift**
Alarm
Alarm
High***
LOW***
<1%
23.5%
19.5%
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