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

    • Headache

    • 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