Gesellschaft für Gerätebau m. b. H

FAQ (Frequently Asked Questions)
Question: What are the disadvantages of electrochemical transmitters?
Answer: Carbon dioxide can be measured by two different detection principles. The electrochemical detection is a low cost detection principle, but leads to high maintenance costs (1 year durability). What is more serious is safety. If the ambient air contains H₂S, the display of the CO₂ transmitter reads a lower CO₂ value than what is actually present, due to cross-sensitivity. Worse case scenario: The transmitter displays a "zero" even though both gases are present! When the sensor drifts, the maximum deviation for the electrochemical sensor (5%), is reached after 10 days. This occurs when the sensitivity of the sensor is extremely high. This means that such a monitor needs to be calibrated every 10 days. This is not practical in the course of business. Moreover, supplying high concentrations of CO₂ to the monitor poisons the electrochemical sensor. In contrast to this, the infrared detection principle has higher initial costs, but longer durability, the smallest maintenance intervals, and no cross-sensitivity to ambient gases.
Question: Can a CO₂ danger be monitored by the oxygen concentration (decline or displacement of the CO₂ concentration)?
Answer: No. The ambient air contains 20% oxygen and 80% nitrogen. If the carbon dioxide concentration increases, oxygen and nitrogen are displaced by the carbon dioxide in a 4:1 ratio. To decrease the oxygen concentration by 1%, the carbon dioxide concentration has to increase by 4%. Oxygen monitors activate the alarm at 17% volume. By this time, the carbon dioxide concentration has already reached a concentration leading to death.
Question: What area can be monitored by one gas transmitter?
Answer: Numerous factors influence this decision: the type of gas, potential leaks, and ventilation all have an influence on the number of transmitters and the mounting places. This question cannot be answered by giving an area in square meters. Please refer to your local GfG sales representative for moreinformation.
Question: Where should a transmitter for ammonia be installed?
Answer: Ammonia (NH₃) is lighter than air. For ammonia monitoring, the transmitter needs to be placed as high as possible. Always make sure that the transmitter is placed higher than every potential leak.
Question: How does a CO₂ sensor with a detection range of 0 to 5% volume react if a much higher gas concentration reaches the sensor; e.g., a short term concentration of 20% volume or higher?
Answer: If the detection range is exceeded, the transmitter gives a signal that can not be overruled by the monitor. The monitor (e.g. G750 or GMA 101) will display that the gas concentration is over range. GfG uses only infrared sensors (IR) for carbon dioxide monitoring. These transmitters cannot be damaged, even by high CO₂ concentrations.

FAQ (Frequently Asked Questions)

Question:
What are the disadvantages of electrochemical transmitters?

Answer:

Carbon dioxide can be measured by two different detection principles. The electrochemical detection is a low cost detection principle, but leads to high maintenance costs (1 year durability). What is more serious is safety. If the ambient air contains H₂S, the display of the CO₂ transmitter reads a lower CO₂ value than what is actually present, due to cross-sensitivity.

Worse case scenario: The transmitter displays a "zero" even though both gases are present! When the sensor drifts, the maximum deviation for the electrochemical sensor (5%), is reached after 10 days. This occurs when the sensitivity of the sensor is extremely high. This means that such a monitor needs to be calibrated every 10 days. This is not practical in the course of business. Moreover, supplying high
concentrations of CO₂ to the monitor poisons the electrochemical sensor.

In contrast to this, the infrared detection principle has higher initial costs, but longer durability, the smallest maintenance intervals, and no cross-sensitivity to ambient gases.

Question:
Can a CO₂ danger be monitored by the oxygen concentration (decline or displacement of the CO₂ concentration)?

Answer:

No. The ambient air contains 20% oxygen and 80% nitrogen. If the carbon dioxide concentration increases, oxygen and nitrogen are displaced by the carbon dioxide in a 4:1 ratio.

To decrease the oxygen concentration by 1%, the carbon dioxide concentration has to increase by 4%. Oxygen monitors activate the alarm at 17% volume. By this time, the carbon dioxide concentration has already reached a concentration leading to death.

Question: What area can be monitored by one gas transmitter?

Answer: Numerous factors influence this decision: the type of gas, potential leaks, and ventilation all have an influence on the number of transmitters and the mounting places. This question cannot be answered by giving an area in square meters. Please refer to your local GfG sales representative for moreinformation.

Question:
Where should a transmitter for ammonia be installed?

Answer: Ammonia (NH₃) is lighter than air. For ammonia monitoring, the transmitter needs to be placed as high as possible. Always make sure that the transmitter is placed higher than every potential leak.

Question:

How does a CO₂ sensor with a detection range of 0 to 5% volume react if a much higher gas concentration reaches the sensor; e.g., a short term concentration of 20% volume or higher?

Answer:

If the detection range is exceeded, the transmitter gives a signal that can not be overruled by the monitor. The monitor (e.g. G750 or GMA 101) will display that the gas concentration is over range. GfG uses only infrared sensors (IR) for carbon dioxide monitoring. These transmitters cannot be damaged, even by high CO₂ concentrations.