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   Updated: 12 Sep 2018
 

 

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GAS DETECTION - CARBON DIOXIDE (CO2), COMBUSTIBLE

   

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:

  • Level value: 5000 ppm

  • 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.

References


IP65, Wall design


IP65, Duct design


IP65, Carbon dioxide with display


 

 

 

 

 


 

Meticulous (infrared) detection
This detector is very selective measuring a selected gas at a specific absorbtionsband in the infrared wavelength area - no false alarms.

Simply put, an infrared detector can measure tgases whose molecules contain more than one atom.

This means that gases such as carbon dioxide, carbon monoxide, methane, sulfur dioxide, etc. can be measured with an infrared detector while the gases like oxygen, hydrogen and chlorine can not be measured with an infrared detector.

Various gases absorb infrared radiation at different frequencies and it is by measuring how much infrared radiation at a specific frequency that is absorbed by the gas in question that you can determine the gas concentration.

A major use for this testing method is when you want accurate readings at low values without false alarms from other gases.

References

   

E-mail: ewert@automatikprodukter.se     

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