Most available sensors detect nitrous oxide in its gas form, immediately upon emission from the water phase. However, nitrous oxide measurements directly in water are also possible, using a miniaturized Clark-type sensor (see e.g., Unisense). A Clark-type sensor, also known as a Clark electrode, is an electrochemical sensor which was invented by British biochemist Leland C. Clark in the 1950s and has since been widely used in various applications, including environmental monitoring, medical devices, and research. The basic principle behind a Clark-type sensor involves the electrochemical reaction that occurs at the sensor's electrodes. The sensor typically consists of two electrodes submerged in an electrolyte solution. One electrode is a working electrode made of a noble metal like platinum, and the other is a reference electrode.

Other commonly used detection techniques for the detection of nitrous oxide include infrared spectroscopy, Tunable Diode Laser Absorption Spectroscopy (TDLAS), electrochemical or semiconductor gas sensors, or colorimetric detection. Technology suppliers for the water industry include Hatech, Teledyne, or Horiba.

This video from Australia is an example of how wastewater treatment monitoring of greenhouse gases can be approached. They use a gas monitor to determine the emission of nitrous oxide during the biological treatment step, and the video clearly shows how it is done.