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KBF-S / KBF-S-UL (E6) 02/2019 page 14/91
1.9 Resistance of the humidity sensor against harmful substances
The following list of harmful substances refers only to the humidity sensor and does not include any other
materials incorporated in the chamber or prohibited substances in relation to explosion protection.
Some gases - especially clean gases - do not have any influence on the humidity sensor. Others do have
a very small influence, whereas others may influence the sensor to a larger extent.
• The following gases do not influence the sensor and the humidity measurement: Argon (Ar), carbon
dioxide (CO
2
),helium (He), hydrogen (H
2
), neon (Ne), nitrogen (N
2
), nitrous oxide (N
2
O), oxygen (O
2
)
• The following gases do not or to a minor extent influence the sensor and the humidity measurement:
Butane (C
4
H
10
), ethane (C
2
H
6
), methane (CH
4
), natural gas propane (C
3
H
8
)
• The following gases do not, or to a minor extent influence the sensor and the humidity measurement,
provided that the indicated loads are not exceeded:
Maximum work place
threshold limit value
Tolerated concentration
with permanent load
Substance
Formula
ppm
mg/m
3
ppm
mg/m
3
Ammonia
NH
3
20
14
5500
4000
Acetone
CH
3
COCH
3
500
1200
3300
8000
Benzene
300
1200
150000
Chlorine
Cl
2
0.5
1.5
0.7
2
Acetic acid
CH
3
COOH
10
25
800
2000
Ethyl acetate
CH
3
COOC
2
H
5
400
1400
4000
15000
Ethanol
C
2
H
5
OH
500
960
3500
6000
Ethylene glycol
HOCH
2
CH
2
OH
10
26
1200
3000
Formaldehyde
HCHO
0.3
0.37
2400
3000
Isopropanol
(CH
3
)
2
CHOH
200
500
4800
12000
Methanol
CH
3
OH
200
260
3500
6000
Methyl ethyl ketone
C
2
H
5
COCH
3
200
590
3300
8000
Ozone
O
3
0.1
0.2
0.5
1
Hydrochloric acid
HCl
2
3
300
500
Hydrogen sulphide
H
2
S
10
15
350
500
Nitrogen oxides
NOx
5
9
5
9
Sulphur dioxide
SO
2
5
13
5
13
Toluol
C
6
H
5
CH
3
100
380
1300
5000
Xylene
C
6
H
4
(CH
3
)
2
100
440
1300
5000
These values are to be considered as approximate values. The sensor resistance largely depends on
the temperature and humidity conditions during the time of exposure to harmful substances. Avoid
simultaneous condensation. Tolerated error of measurement: +/- 2 % r.h. The maximum work place
threshold limit value is one that can be regarded as harmless for humans.
• Vapors of oil and fat are dangerous for the sensor because they may condensate at the sensor and
thus prevent its function (insulating layer). For similar reasons it is not possible to measure smoke
gases.
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