Measuring O3 Output

25th Apr 2020

How to Measure Ozone Output

We are commonly asked how to measure output or verify that an ozone generator produces the amount of ozone the manufacturer claims. This tech sheet will cover how to measure the output of your high concentration ozone generator.

It is key to understand that the output of an ozone generator is almost always measured in grams per hour (g/hr), also known as ozone output. The ozone measurement instrument will read Ozone Concentration: % by weight or grams per meter cubed (g/m3). To mathematically determine the g/hr (Ozone Output) from % by weight or g/m3 (Ozone Concentration), you will need to determine the flow rate of the ozone generator in liters per minute (lpm). 

The calculations to use when you have determined the gas flow rate and concentration are below:

From % by weight using oxygen as a feed gas:

Ozone Output (g/hr) = (( lpm x 0.001) x 60) x (14.3 x % by weight)

From % by weight using dry air as a feed gas:

Ozone Output (g/hr) = (( lpm x 0.001) x 60) x (12.8 x % by weight)

From g/m3:

Ozone Output (g/hr) = ((lpm x 60) x 0.001) x g/m3

Another resource we offer is a handy online calculator. Just enter your flow and concentration values and we do the work!

Note: When using % by weight to measure ozone concentration, the calculation to determine Ozone Output is different because the density of the gas is different. Due to the difference in the density of the gas, there are separate conversion formulas used to determine the output of an ozone generator (as shown above).

Ozone Measurement Device

A related question is which ozone measurement device should be used to facilitate these measurements. The short answer is, only a high concentration ozone analyzer. Note that the units of measure used are: % by weight and g/m3. This is due to the high concentrations of ozone produced by most ozone generators. We are also asked why parts per million (ppm) is not used as a unit of measure. Let me provide a quick example using a very small ozone generator.

An ozone generator producing 2 g/hr ozone from 10 lpm of air would produce 0.26% ozone concentration.

2 g/hr = ((10 lpm x 0.001) x 60) x (12.8 x 0.26% by weight)

0.26% ozone = 1573 ppm conversion info here

At only 2 g/hr of ozone output the ppm value is already 1573 ppm. The parts per million (ppm) unit of measure is just not conducive to these calculations. Therefore, it is rarely, if ever; used when calculating generator output.

The high concentrations that are created limit the number of ozone measurement devices that can be used, which is why the process is restricted to high concentration UV ozone analyzers.

Components Needed

  • Mass Flow Meter will measure overall gas flow accurately for a flow measurement
  • 0 - 2 ppm Flow Meter will regulate and measure gas flow through the ozone analyzer
  • Ozone Analyzer will measure the ozone concentration in % by weight or g/m3
  • Ozone Destruct Unit will convert ozone back to oxygen to safely be vented into the air

Other Important Considerations

When choosing an ozone analyzer, ensure that the analyzer you are purchasing operates within the range that you will be operating within. Some ozone analyzers are limited to low ranges only, so ensure that you choose a device capable of reading a higher concentration of ozone than you will ever need to measure.

Also ensure that the analyzer you are purchasing will measure ozone concentration using the units of measure that you desire. If choosing an analyzer that measures ozone in percent (%) by weight, be sure to specify whether you are using oxygen or dry air gas. Some analyzers may be only factory configurable and cannot be configured by the user.

Gas flow is a very critical component of the calculations used to measure ozone output. A small deviation in actual flow measurement will result in a large error in the resulting ozone output figure. Since this is such an important value, we recommend using a high quality Mass Flow Meter to measure the total gas flow entering the ozone generator. A mass flow meter will measure total gas flow. This measurement is also pressure compensated to eliminate that potential variable. Using the mass flow meter prior to the ozone generator will remove the possibility of ozone corroding the delicate components inside the mass flow meter.

Most high concentration ozone analyzers will only require a very small gas flow rate. This will require a small flow meter to regulate and measure that gas flow. An advantage of this small flow rate is that the ozone analyzer could be used as an on-line measurement device. If the ozone generator uses a gas flow rate of 20 lpm and the analyzer will only consume 1 lpm for accurate measurement, this set-up only requires a 5% slipstream of the ozone gas.