Not all ozone detection devices are created equal! This page compares the various technologies that are commonly used to detect ozone: Electrochemical sensors, semiconductor-based sensors (HMOS / GSS), UV absorption, and color-change badges.
Read on to discover the details of each technology, and find our side-by-side comparisons below.
Diagram of an Electrochemical Sensor
An electrochemical ozone sensor uses a porous membrane that allows ozone gas to diffuse into a cell containing electrolyte and electrodes. When ozone comes into contact with the electrolyte, a change in electrochemical potential occurs between the electrodes causing electrons to flow.
In zero air, little or no electron flow occurs. As the presence of ozone increases, the electrical signal increases proportionally. The monitor interprets this signal and displays the ozone concentration in PPM (parts per million).
A heated metal oxide semiconductor (HMOS) sensor works by heating a small substrate to high temperature (around 300-deg F / 149-deg C). At this temperature, the substrate is very sensitive to ozone and exhibits a change in resistance that is proportional to to the amount of ozone which contacts its surface. The circuitry of the monitor interprets this change in resistance and displays the corresponding ozone level on the display as either PPM or PPB.
An Ozone molecule has a UV absorption maximum at 254 nm. In a controlled environment, this means that the amount of 254 nm UV light absorbed in an airspace is proportional to the amount of ozone present.
UV ozone analyzers take advantage of this property of ozone for stable, accurate readings. A UV lamp emitting light at a wavelength of 254 nm produces a controlled amount of light within a sealed chamber. This UV light is measured via a photodiode that is also filtered to detect at the 254 nm wavelength.
The difference in UV light produced at one end of the chamber, vs the UV light measured at the other end of the chamber indicates the concentration of ozone in the air sample which is then displayed on-screen or output to a control system.
Ozone badges are cards that use a color change indicator. The indicator used is a small paper strip or circle that is oxidized in the presence of ozone. The amount of oxidation (color change) that occurs during a set amount of time is proportional to the amount ozone present in the air.
Now that you have an overview of the various technologies, you may want to know how they rate for various metrics. See the lists below!
(Descending order, from best to least)
(Descending Order, Highest to Lowest)
(Descending Order, widest operating band to narrowest)
Last Updated: December 28, 2012
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