Applied Nanotech Holdings is a manufacturer of gas sensors. Their Metal Nanoparticle sensors are palladium nanoparticle-based hydrogen sensors. Their Sono Photonic gas sensors can detect trace amounts of most gases and vapors.

Parallax Inc. is an online seller of gas sensors. They offer CO2 sensors for industrial and automotive applications. The CO2 Gas Sensor Module is designed to allow a microcontroller to determine when a preset carbon dioxide level has been reached. The CH4 are methane gas sensors, also using a microcontroller for preset levels of methane..

Global Water Instrumentation, an ITT company, manufactures the WQ401 model dissolved oxygen gas sensors. Features include 4-20 mA output, a range of 0-100% saturation, 0-8 ppm, temperature compensated to 77°F (25°C), and accuracy of ±0.5% of full scale.

NTM Sensors is a designer and manufacturer of gas sensors. Their new NTM SenseH2 Hydrogen sensor is designed for hydrogen monitoring. It is accurate, stable, rapid and durable. The NTM Alarm System is a complete hydrogen monitoring solution.

Vernier offers CO2 and oxygen gas sensors. The CO2 gas sensor measures gaseous carbon dioxide in two ranges–0 to 10,000 ppm and 0 to 100,000 ppm. The oxygen gas sensor can be used to monitor gaseous oxygen levels in  biology and chemistry applications.