Which method uses chemiluminescence to monitor NOx?

Which method uses chemiluminescence to monitor NOx?

• A. Chemiluminescence
• B. NDIR
• C. UV photometry
• D. Amperometric sensor

Answer: (A)

Chemiluminescence detects NOx by measuring light emitted from a chemical reaction. In this method, nitric oxide (NO) reacts with ozone to form excited NO2 (NO2*), which releases photons as it returns to the ground state. The intensity of that light is proportional to the amount of NO in the sampled air. To measure total NOx, NO2 can be converted to NO before the reaction, so all NOx contributes to the light signal. This is why chemiluminescence is the technique that uses light emission to monitor NOx. Other methods rely on different principles—NDIR uses infrared absorption, UV photometry uses UV interactions, and amperometric sensors rely on electrochemical current—so they don’t involve chemiluminescence.

Chemiluminescence detects NOx by measuring light emitted from a chemical reaction. In this method, nitric oxide (NO) reacts with ozone to form excited NO2 (NO2*), which releases photons as it returns to the ground state. The intensity of that light is proportional to the amount of NO in the sampled air. To measure total NOx, NO2 can be converted to NO before the reaction, so all NOx contributes to the light signal. This is why chemiluminescence is the technique that uses light emission to monitor NOx. Other methods rely on different principles—NDIR uses infrared absorption, UV photometry uses UV interactions, and amperometric sensors rely on electrochemical current—so they don’t involve chemiluminescence.