Which gas sensor is appropriate for indicating the presence of nitrogen dioxide?

The electrochemical cell is the most suitable choice for detecting nitrogen dioxide (NO2) due to its specific design and operational principles. Electrochemical sensors work by measuring the current produced during a chemical reaction between the gas and the sensor materials. This reaction occurs when the nitrogen dioxide interacts with the electrodes of the cell, producing a measurable electrical signal that correlates directly to the concentration of NO2 in the environment.

Moreover, electrochemical cells are known for their sensitivity and selectivity toward target gases, including nitrogen dioxide, making them particularly effective for monitoring NO2 levels in various settings. They are often used in air quality monitoring applications due to their ability to provide real-time data on harmful gases, including nitrogen dioxide, which is a significant air pollutant.

The other sensor types mentioned are less ideal for detecting nitrogen dioxide. Catalytic combustion sensors are better suited for flammable gases rather than toxic gases like NO2. Infra-red analyzers, while effective for detecting gases that absorb infrared radiation, may not be as sensitive to NO2 specifically. Flame ionization detectors are typically used for hydrocarbons and are not suited for measuring inorganic gases such as nitrogen dioxide. Consequently, the electrochemical cell stands out as the best option for indicating the presence of nitrogen dioxide.