ozone color

The Color of Ozone

Does ozone gas have a color? Yes, the color is blue. The problem is, ozone is normally found in gas, or in water at such low concentrations that the color is not visible.

Recently we performed some lab testing that required ozone levels in water greater than 100 ppm. The picture below provide some great examples of the color of ozone.


ozone color
0 ppm ozone on left vs >100 ppm ozone on right


Ozone in water
The Color of Ozone is visible in this image


ozone in water
An ATI Q45 Dissolved Ozone Monitor was used to measure dissolved ozone in water. The blue color of the water is even slightly visible in the flow cell used to measure ozone.


Dissolved Ozone in water
AS the dissolved ozone level increases the color of the water gets darker. The blue color in the water starts to become visually evident above 50 ppm.


Ozone levels in water turn water blue
The blue color of ozone is more visual in larger containers like this 1-gallon water jug.


Ozone Properties

The table below provides additional information on the properties of ozone. This shows the color of ozone is light blue, which is true. It is only visibly blue when ozone gas or ozone in water is at a very high concentration.

Property Ozone Oxygen
Molecular Formula O3 O2
Molecular Weight 48 g/mol 32 g/mol
Color Light blue Colorless
Smell Odor threshold of 0.001 ppm, pungent at high levels Odorless
Melting Point -192.5 deg C -218.79 deg C
Boiling point -111.9 deg C -1892.95 deg C
Critical Temperature -121 deg C -118.56 deg C
Critical Pressure 54.5 atm 5.043 atm
Density 2.144 g/l @ 0 deg C 1.429 g/l @ 0 deg C
Solubility @ 0 deg C 0.64 g/100 ml 0.049 g/100 ml
Electrochemical Potential 2.07 V 1.23 V


Ozone Solubility

Ozone is only partially soluble into water. The graph below shows the solubility of ozone into water based on water temperature and ozone gas concentration. As the water temperature decreases and ozone concentration increases ozone becomes more soluble into water.

Water pressure is the third and final factor in determining ozone solubility into water. However, as these images were taken of water at ambient pressure, this was not a factor used, and is not a required factor in achieving high ozone levels into water.

Do you have a need to achieve higher ozone levels into water? Or lab testing that requires dissolved ozone levels higher than off-the-shelf equipment can provide? Give us a call, we would be glad to help.


13 thoughts on “The Color of Ozone”

  1. Pingback: Cool Colors in Oxidation - Oxidation Technologies News

  2. Jennifer Coleman

    I was wondering if you could help me figure a problem out. Please I am running a small water bottling facility and when I run my water straight from the well into the surge tank it is crystal clear, but as soon as I run it through the Ozonation system the water is turning a brownish color. Could you please help me figure out what the issue is. Anything will help! Thankyou,
    Jennifer Coleman

    1. This is likely caused by manganese oxidation. Manganese (Mn) can oxidize to Permanganate (Mn04) this will turn the water a brown, or even purple color. If there is also some iron in the water it would turn more of a brown color.

      If you have a water quality test we can review, we could likely help further by identifying what is in the water that could oxidize.

  3. We also have the same issue here.
    Running a water plant but at times the water becomes brown.
    When we try cleaning the OZONE CAN the brownish reduces but not to ZERO.

  4. I live in Julian CA 92036. We get our water from a private well on our property. We have used an Ozone generator for many years to precipitate out microbial iron in the water. Without the Ozone, the water turns a terracotta brown color. With the Ozone, it is clear. About a week ago, the water in our house started turning a light purple. And, when I look into the tank with the Ozone generator, it is a darker purple. As an aside, the well water first goes into another storage tank without an Ozone generator and that water is a typical, cloudy brown. So, can you speculate as to why the water turned purple after so many years? And, is the light-purple water that comes out of the tap in our home dangerous to drink, cook with and/or bathe in? Any insight or references you can provide would be greatly appreciated! I have photos if you are interested.

    1. The purple color indicates there is manganese in the water. Ozone oxidizes Manganese (Mn) to MnO2 which is insoluble and can be effectively filtered from the water. However, excess ozone, and most commonly, excess contact time will further oxidize to Permanganate, Mn (VII). This is a soluble form of manganese that has a purple color to it.

  5. Hello,
    I have a ozone generator and a 10000 liter water tank, i want to reach 0.5ppm disolved ozone in water, but if i turn off the ozone generator and immediately test the water, the indicator show a very low dissolved ozone, I used venturi to inject ozone to water, how can I increase amount of dissolved ozone?

    1. Morteza,

      You did not state the ozone production capacity of your ozone generator. This will be critical information.
      10,000 liters of water @ 0.5 mg/l ozone = 5,000 milligrams of ozone, or 5 grams of ozone necessary in the water to mathematically achieve 0.5 mg/l. If the water in this tank has a half-life of 20-minute, every 20-minutes 50% of the 5 grams of ozone will decay naturally back to oxygen this is a decay rate of 2.5 grams of ozone every 20-minutes, or 7.5 g/hr. (half-life will be a factor of water temperature and quality). If 7.5 g/hr ozone is required to overcome half-life we need more ozone production to build up to the 5 grams of ozone in the tank. Then, as you suggest there are solubility issues and general inefficiencies. Therefore, figure at least 15 g/hr of ozone will need to be produced to achieve 0.5 mg/l in 10,000 liters of water. Are you producing at least 15 g/hr of ozone? If so, use numbers above to determine where your inefficiencies may be and determine if you need more ozone, or better solubility.

  6. We just had an ozone machine added to our well water system. I have highlights (blonde) in my hair and now my hair is turning green! Could this be the ozone equipment?!

    1. Ozone would not turn har green. However, chlorine would.
      What else is in place for water treatment? Ozone only? There is certainly more to this story. Glad to help, but would need more details to determine the root cause.

  7. Good afternoon,

    We are an indoor agriculture farm
    We do have an ozone skid we use to clean our pipes in between fertigation our target is about 600mv. However we are having an issue where our MV rises quickly as soon as the ozone generator kicks on, it will shoot to over 1.000mv in minutes
    However when I test for dissolved oxygen I am not seeing anything
    I did test to make sure there was no stray voltage
    I have isolated the MV issue to the ozone skid itself.

    Thank you for any help

    1. If the ORP is high it may be mostly reactive oxygen species that are reacting with organics in water.
      You state you are testing for dissolved oxygen and find nothing, that is not likely. I assume it is simply a lower reading, or unchanged reading?
      If so, I would need more info, there are solutions, but would need to get to root of the “whyy”.
      Feel free to call or e-mail our office:

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