Planning
Technical CO alarm
4
56 | 94
Building Technologies
A6V10209291_h_en_--
Fire Safety
2016-03-03
4.3 Technical CO alarm
NOTICE
The system is not controlled as laid down in EN 54-2
Infringement of the EN 54-2 standard.
The signals for CO detection alone must not be used to control fire detection
equipment in accordance with EN 54-2.
4.3.1 Ambient features
In selecting the optimum parameter set for CO, the following factors must be taken
into account:
Positioning the point detector
CO is slightly less dense than air and spreads evenly though the room when at a
constant temperature.
However if CO is produced in a fire, it is warmer than the surrounding air and rises
towards the ceiling with the smoke. If the point detector is used as a fire detector
for this situation, the same positioning rules apply to it as for a fire detector.
If the point detector is used for the 'Technical CO Alarm' and CO is produced from
cold sources, the point detector can either be installed on the ceiling or on the wall
at head height. Cold sources include e.g. gas cylinders in a laboratory. The
positioning rules for gas detectors must be consulted for more details.
Influence of the surroundings
At temperatures in excess of +50 °C, the CO sensor ages faster than expected and
the guaranteed 5-year service life for the point detector is reduced.
If the rooms requiring protection constantly have concentrations of ethanol of up to
500 ppm (= MAK value for ethanol), e.g. in breweries or whisky distilleries, since
the electro-chemical cells have slight cross-sensitivity to ethanol, the 'Technical CO
Alarm' is more likely to experience false alarms.
In a very dry and very hot climate, the response time of the CO sensor increases to
around 120 s. The response of the point detector to relatively slow increases in the
CO concentration, e.g. in the event of fires, is not therefore affected. But very quick
increases in the CO concentration are detected with a slight delay.
The CO sensor responds faster in very humid air than air of normal humidity. There
are no limits here on use as a fire detector or for the 'Technical CO Alarm'.
The electro-chemical CO sensor of the point detector has a slight cross-sensitivity
to hydrogen (H
2
), i.e., H
2
also causes CO signals. As H
2
can be produced when
charging lead batteries and in electroplating plants, robust parameter sets which
only cause an alarm when increased CO concentrations are detected should be
used in such environments.
