Ozone Safety Concerns


Gaseous Ozone

 -Ozone in the air can be harmful at high levels

 -Short term health effects will be noticeable:

     *Shortness of breath


     *Harsh breathing

     *Severe pain in lungs (at levels above 1.0 ppm)


Aqueous Ozone

 -No major health concerns, aqueous ozone is very stable

 -Drinking aqueous ozone may create upset stomach

 -Gaseous ozone can off-gas into the air from aqueous ozone


*Ozone in air will react differently than ozone in water, therefore no major health risks exists with aqueous ozone. However, it is possible for ozone to off-gas from the water into the air, creating gaseous ozone from aqueous ozone. Keep this in mind when working with aqueous ozone.*


Ozone Regulations


OSHA (Occupational Safety and Health Administration)

  *OSHA Permissible Exposure Limit (PEL) guidelines for O3 in the workplace are based on time-weighted averages (TWA). 0.1 ppm for 8 hour work shift for a 40 hour work week.*

 -OSHA requires that if you are generating ozone that you measure this ozone level for safety purposes

 -The OSHA website cites the following exposure limits for ozone in the workplace:

     *0.1 ppm PEL for 8 hours per day (TWA) exposure for General Industry

     *0.1 ppm PEL for 8 hours per day (TWA) exposure for Construction Industry

     *0.1 ppm PEL for 8 hours per day (TWA) exposure for Shipyard Employment

     *0.3 ppm Short Term Exposure Limit (STEL) for a 15 minute time weighted average (TWA) exposure which is not to be exceeded at any time during a workday even if the time-weighted average is below the PEL.


Below is the calculation that can be used for the cumulative exposure for the 8 hour work shift:

          (Ca Ta+Cb Tb+. . .Cn Tn)÷8 = E
     *E is the equivalent exposure for the working shift. (Ozone = 0.1 ppm)
     *C is the concentration during any period of time (T) where the concentration remains constant.
     *T is the duration in hours of the exposure at the concentration C.

  For example:
          ([0.5ppm x 1 hour] + [0.02 x 2 hours] + [0.052ppm x 5 hours]) ÷ 8 = 0.1 ppm

Ozone levels can be higher than the 0.1ppm standard for a short period of time as long as low levels at other times of the day still equal out to 0.1ppm of ozone over the 8 hour shift.

  For example (0.1 all day):
          (0.1ppm x 8 hour) ÷ 8 = 0.1

When using this calculation the value of E should never exceed 0.1 ppm of ozone in an 8 hour work shift.

For more information see the OSHA web page regarding ozone:



NIOSH (National Institute for Occupational Safety and Health)

*NIOSH safety and health standards are not enforceable under US law. NIOSH does “develop recommendations for health and safety standards” that may influence future law and OSHA regulations.*

-Max recommended exposure limit is 0.1 PPM

-Ozone levels of 5 PPM or higher are considered immediately dangerous to life or health

-Respirator Recommendations:

     *Up to 1 ppm

     *Any ozone rated cartridge respirator

     *Any supplied air respirator

           Up to 2.5 ppm

      *Any supplied air respirator operated in a continuous flow mode

      *Any powered air purifying respirator

           Up to 5 ppm

      *Add face mask to respirator

          Entrance into unknown concentrations

      *Self contained breathing apparatus with full face mask



EPA (Environmental Protection Agency)

*The EPA measures, tracks, reports, and regulates ground level ambient ozone levels in large cities throughout the United States.*

Good Up High, Bad Nearby

Ground level ozone:

     -Ozone near the ground is considered pollution by the EPA and is regulated

Ozone generators that are sold as air cleaners:

      -EPA does not recommend, or regulate ozone generators, it does offer safety information

Ozone Air Quality Standards:

     -Primary and secondary ozone standard levels are 0.070 ppm -

     -Primary standards set limits to protect public health, including the health of "sensitive" populations such as asthmatics, children, and the elderly.

     -Secondary Standards set limits to protect public welfare, including protection against visibility impairment, damage to animals, crops, vegetation, and buildings.

     -Link for Ozone safety standards from the EPA


National Ambient Air Quality Standard for Ground-Level Ozone

Ozone 0.07 ppm 8-hour


Ozone Measurement Basics

 -Ozone is heavier than air and can sink

 -Ozone has a low vapor pressure and so it does not try to fill the room uniformly.

     *This makes ozone difficult to find and potentially unsafe ozone levels in one area while others are safe

     *Ozone leaks are difficult to find due to this tendancy

 -Ozone tends to cling to rough surfaces such as fabrics

     *While you may smell ozone residual with your nose, your detector finds no ozone. This may be confusing at times

 -Ozone reverts back to oxygen with a "half life" typically of 10-30 minutes.

 -Ozone has a sweet smell, but the odor threshold varies widely by the person and by ambient conditions. Therefore "smell" is not a reliable test for the presence or concentration of ozone.

 -Senses can be desensitized to ozone very quickly, always use high quality ozone gas detectors for safety, your nose is not acceptable.

 -Most Important  - What is the ozone concenctration at the breathing level where the room occuptants will be?

 -Link to - Tech tip from EcoSensors on measuring ozone in air

 -Link to - Tech tip on measuring ozone in room with ozone generator


Oxidation Tech offers a full range of ozone monitors.

C16 Sensor in Hand

Handheld Ozone Monitors

Aeroqual SM70 ozone sensor

Fixed Ozone Detectors

OZ-2 Dissolved Ozone Test Kit

Measure ozone in water

A23-14 Ozone Calibration Kit

Ozone Monitor Accessories

Plug-in Smart sensor

Replacement Ozone Sensors



Important Concepts Regarding Ozone Safety

 -Odor threshold of ozone is ~ 0.02 – you can smell ozone before it will harm you

 -Effects of ozone exposure are a function of time and concentration

 -First aid:

     Low level exposure – get fresh air

     High level exposure – seek medical attention

 -Fix leaks