What gases and chemicals to avoid when using Zirconium Dioxide Oxygen Sensors?

Cross sensitivity is a common concern with many oxygen sensors, making it crucial to identify the underlying causes to safeguard your zirconium dioxide oxygen sensor against potential contamination. Understanding which gases and chemicals adversely affect Zirconium Dioxide Oxygen Sensors is imperative for maintaining their longevity and performance. This article delves into the specific gases and chemicals to avoid when utilizing Zirconium Dioxide Oxygen Sensors.

1. Combustible Gases:

Even trace amounts of combustible gases undergo combustion at the sensor's hot Pt-electrode surfaces or AI₂O₃ filters. While combustion is typically stoichiometric with sufficient oxygen, it can lead to measurement errors by altering the residual oxygen pressure. Applications with substantial combustible gas presence requiring precise oxygen measurements should refrain from using these sensors. SENSAGAS has scrutinized gases such as:

- H2 (Hydrogen) up to 2%; undergoing stoichiometric combustion

- CO (Carbon Monoxide) up to 2%; undergoing stoichiometric combustion

- CH4 (Methane) up to 2.5%; undergoing stoichiometric combustion

- NH3 (Ammonia) up to 1500ppm; undergoing stoichiometric combustion

2. Heavy Metals:

Vapors emitted by metals like Zn (Zinc), Cd (Cadmium), Pb (Lead), Bi (Bismuth) can impact the catalytic properties of the Pt-electrodes, necessitating avoidance of exposure to these metal vapors.

3. Halogen and Sulphur Compounds:

Minimal concentrations (<100ppm) of Halogens and/or Sulphur compounds don't affect zirconium dioxide oxygen sensors. However, elevated levels over time may lead to readout issues or, particularly in condensing environments, corrosion of sensor components. SENSAGAS has examined gases including:

- Halogens: F2 (Fluorine), Cl2 (Chlorine)

- HCL (Hydrogen Chloride), HF (Hydrogen Fluoride)

- SO2 (Sulphur Dioxide)

- H2S (Hydrogen Sulphide)

- Freon gases

- CS2 (Carbon Disulfide)

4. Reducing Atmospheres:

Prolonged exposure to reducing atmospheres can degrade the catalytic effect of Pt-electrodes. Reducing atmospheres are characterized by minimal free oxygen and the presence of combustible gases, resulting in oxygen consumption as these gases combust.

5. Other Considerations:

SENSAGAS's oxygen sensors were primarily designed for boiler combustion control applications. Life tests have been conducted in various environments, including laboratory atmospheres and exhaust gases from natural gas-fired boilers and light oil.

In conclusion, Zirconium Dioxide Oxygen Sensors exhibit cross sensitivity to specific gases, substances, and chemicals present in the environment. To optimize sensor performance and lifespan, heed the recommendations outlined in this article. It's important to note that while these are the gases, chemicals, and substances SENSAGAS has tested, if your application environment contains unlisted gases, it's advisable to conduct sensor testing to ensure optimal functionality.