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MK LIT (E5) 01/2021 page 41/172
7.8 Gas detection
Gas detection is only active when the main switch (10) of the gas detection system is activated
(ON position).
Gas detection (measurement of atmospheric composition in the interior of the chamber) is used to deter-
mine the start of a EUCAR hazard level 4 to 6 event. When predefined thresholds are reached, warnings
or alarms are triggered via the alarm center (chap. 13.1). If a limit value for alarm level 2 is exceeded, the
CO
2
fire suppression system is activated.
H
2
and O
2
are produced when a defective battery is outgassed. If a fire or flame
develops, CO (flue gas) is released.
The concentration of these three gases is monitored by means of sensors when
gas detection is activated via the main switch of the gas detection system (ON
position).
Figure 10: Gas detection system main switch (OFF position)
Switching thresholds of the sensor systems
Notification level 1 Notification level 2
O
2
* 25 vol.-% 30 vol.-%
H
2
100 ppm 200 ppm
CO 30 ppm 60 ppm
* Switching thresholds can be individually configured, e.g., release of the higher-level control system
Notification level 1: Warning, the indicator light flashes yellow
Notification level 2: The indicator light flashes red, the CO
2
fire suppression device is activated
An air sample is continuously taken from inside the battery test chamber and monitored for the gases O
2
,
H
2
, and CO.
The air flow from inside is supplied directly to the O
2
sensor. The oxygen concentration is displayed on the
evaluation unit in vol-% O
2
.
The air flow is then diluted 1:1 with dilution air (filtered ambient air) to the H
2
and CO measuring sensors.
The concentration of these gases is displayed on the evaluation unit in ppm. The dilution of the air flow is
necessary to ensure that the H
2
and CO sensors receive sufficient oxygen to accurately measure the con-
centration of the gases.
Downstream of the pump, the air flow is returned to the interior of the battery test chamber. The dilution air
and measuring gas volumetric flows are monitored by means of flow meters with ring initiators. A deviation
from the volumetric flow set point will result in a fault notification and activation of the yellow indicator light
(flashing signal).
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