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CO2 Carbon dioxide
Carbon dioxide is usually found in the atmosphere in a
concentration of about 400 ppm and is formed for example in
combustion or in fermentation processes (breweries, etc.).
It is odour and colourless.
The carbon dioxide can not be detected with electrochemical sensors.
Usually a "Lite" IR sensor is used.
Also sensors which measure the gas thermal conductivity can
sometimes be used.
The greatest danger with increasing CO2 concentration is
that the oxygen in the air is partly substituted, with hypoxia as a
result, but beyond this, carbon dioxide also has a toxic effect.
Hygiencic threshold limit values:
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Level value: 5000 ppm
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Maximum value: 10000 ppm
Alarm is normally set at these threshold levels with the level value
as the first alarm limit and the short-term value as the second
alarm level.
Even at a few percent carbon dioxide, the respiration increases
dramatically.
Symptoms include headache, dizziness, rapid pulse and nausea.
Concentrations over of about 10% can be very dangerous.
In areas with poor ventilation and where there are many people there
may occur problems due to increased carbon dioxide levels (from the
breath).
In workplaces one seeks to reduce carbon dioxide concentration to
below 1000ppm.
Sensor Placement
Carbon dioxide is heavier than air (higher density) which means that
it can easily be collected in low-level areas.
The concentrations of these spaces may therefore be very high and it
can dangerous to step down / in such an area without ensuring that
the oxygen concentration is high enough (20.9% oxygen).
Stationary sensors are therefore placed low, with possible additions
of sensors at the likely leakage points.
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