Ambient Ozone Monitors

Ozone leaks around an ozone generator or the associated equipment can create a safety hazard for operators of the equipment. While ozone can be detected at concentrations well below those that are considered dangerous, it is a good idea to have at least one ambient ozone monitor.

These unit will have th option for alerting the operator to low level leaks with an indicator light or audible alarm and at higher levels will shut down the ozone generator. There are several types: UV photometers, electrochemical sensors and solid state sensors that use semiconductor technology. The UV photometer type draws a sample of the ambient air into the unit where UV light is past through the gas sample. UV at the wavelength used does not "see" air or oxygen, but does measure ozone. While such monitors can measure a range of concentration, measurements in the 0-1 ppm range would be the most common with a resolution of 0.001 ppm.

The other technology employs an electrochemical sensor that measure the reaction of ozone that passes through a membrane and contacts a special electrode. The electrochemical sensors are available in ranges similar to the UV monitors, but are somewhat less expensive. They are some what less accurate (+/- 5%). In the case of an ambient monitor such accuracy is probably not important. Both sensor types are widely deployed in ozone water treatment applications.

The final technology employs HMOS (heated metal oxide semiconductor) sensor. The range is .02-.30 ppm. Accuracy is not as high as the other technologies with results of +/- 20%. This requires setting the sensor alarm lower than for the other instruments, but the cost is considerably less, perhaps one third the cost of the electrochemical sensor.

It is important to note that ozone is heavier than air, so ozone will tend to collect in low lying areas. Sensors should be placed closer to the floor or in basement areas below the ozone generators or associated equipment. Hand held versions of ambient ozone monitors can be used as personal warning systems or for locating leaks in an ozone water treatment system