Making Sense of Ozone Measurements

How much ozone is a particular machine making?

How concentrated is the ozone?


One useful way to measure ozone concentration is to state how many parts of ozone are present per million parts of gas (normally air.) We can smell ozone when it is present in the air in as low as .01 parts per million (10 parts per billion). At .1 ppm levels in ambient air, ozone becomes uncomfortable. Industrial ozone generators can produce ozone in concentrations well over 100,000 parts per million. Usually these larger concentrations are expressed in % by weight. 100,000 ppm could be written as 100,000/1,000,000 which is 10/100 or 10%. Because the weight of an ozone molecule is heavier than the other gas molecules making up air, the actual measurement is 13.7 %wt. Parts per million is useful for many applications, but sometimes it is handy to use parts per billion for very low concentrations. The general principle is to reduce the number of zeros when communicating this information. We do the same thing when measuring distance with millimeters or kilometers etc. A good starting point to get a feel for ozone concentration is to become familiar with ppm and %wt. We provide definitions for other common units and links for conversions and calculators at our calculations page.


A second dimension of ozone measurement is the actual quantity of ozone being produced or used. The production of smaller generators is measured in grams per hour. The production of the largest generators is measured in pounds per day. 1 lb/day ozone = 18.89 g/hr ozone. The smallest ozone generators we sell generate less than a half of a gram per hour. That would be about a hundredth of a pound per day which is an awkward figure to use. “Grams per hour” happens to be practical for describing the output of lower production machines. The larger ones we sell generate 1000 grams per hour or 50 pounds per day. Pounds per day happens to be practical for larger machines. A drinking water treatment plant in Texas uses up to 42,900 pounds of ozone per day (over 200 tons). One lightning storm can generate over 200 tons of ozone.


A third dimension of measurement for any gas application is flow rate. When generating ozone, flow rate will affect the ozone concentration. With a given ozone production rate (for example, 200 grams per hour), lower flow rates will result in higher ozone concentrations. Higher flow rates will result in lower concentrations. One useful calculator helps determine the amount of ozone needed to supply a particular concentration at a particular flow rate.  For example, if you need a concentration of 5% by weight and have an oxygen flow of 10 LPM, you will need a generator capable of 43 grams per hour. If the flow doubles to 20 LPM, the concentration is cut in half.

People working with municipal water treatment get used to working with larger units such as pounds per day and high ozone concentrations. People working with sanitation equipment and other mid-scale applications get used to thinking in terms of grams per hour and the whole spectrum of ozone concentration measurements. Those involved in small household applications and generators are more familiar with milligrams per hour and low concentrations. Our system integration experts need to be familiar with the whole spectrum of measurements. Familiarity and precision in application grows with years and diversity of experience. Our online calculator provides a powerful tool for an efficient and effective integration of ozone into your application.

Oxidation Technologies provides equipment, engineering expertise, and service to a wide range of applications and ozone demands. Our service requires flexibility in thinking and a familiarity with the full spectrum of ozone concentrations. We build ozone systems to integrate into your existing industrial process. Every situation has a multitude of variables that will affect the performance.

Give us a call. We’d love to help you harness the power of ozone for your application.  515-635-5854

Measuring Ozone in an Occupied Room

Measuring Ozone in an Occupied Room
ozone concentrations can vary greatly at various locations, and the concentrations are often highest in unexpected places. Key points to consider are:
  • Ozone is much heavier than air and tends to sink to lower levels.
  • Ozone has a low vapor pressure and so it doesnot try to fill the room uniformly. It tends to stay where it is.
  • Ozone tends to cling to rough surfaces such as fabrics and breaks down (converts back to oxygen) when passing through restricted and obstructed passageways.
  • Ozone reverts back to oxygen with a “half life” (time to go to half of its original concentration) typically of 10-30 minutes.
  • Ozone can be confused by instrumentation with other oxidizing gases such as chlorine compounds, acid fumes, and oxides of nitrogen (NOx). Strong “reducing” gases, such as vapors of alcohol and  solvents, can reduce the apparent concentration of ozone.
  • Ozone has a sweet smell, but the odor threshold varies widely by the person and by ambiental conditions. Therefore “smell” is not a reliable test for the presence or concentration of ozone.
The important measurement is:
What is the ozone concentration at the breathing level where room occupants will be?
For ozone introduced via HVAC systems with good room air circulation, the alternate point of measurement is near the entrance to the return air duct.
Suggested ozone Monitors:
A-21ZX Ozone Sensor
A-21ZX Ozone Sensor
C-30ZX Ozone Monitor
C-30ZX Ozone Monitor
OS-6 Ozone Controller
OS-6 Ozone Controller