The Definition of Ozone Exposure

Definition of Ozone Exposure

Ozone exposure is breathing ozone (O₃), a reactive, pale blue gas with a sharp odor that forms when ultraviolet light or electrical discharges split oxygen molecules. In the workplace, ozone is produced by arc welding, especially gas metal arc and gas tungsten arc welding on aluminum and stainless steel, UV curing and disinfection lamps, ozone generators used for water treatment and odor control, and some high-voltage equipment. Ozone irritates the eyes, nose, throat and lungs, and it can reduce lung function even at low concentrations.

Key Facts About Ozone Exposure

• OSHA PEL: 0.1 ppm as an 8-hour TWA.
• NIOSH REL: 0.1 ppm ceiling; the IDLH value is 5 ppm.
• People can smell ozone at very low levels, but the sense of smell fatigues with continued exposure.
• Symptoms include coughing, chest tightness, shortness of breath, headache and worsening of asthma.
• Ozone is used as a disinfectant, but ozone generators shouldn't be used in occupied spaces.

Example of Ozone Exposure

Welders on an aluminum fabrication line complain of chest tightness and throat irritation. Air monitoring near the arc shows elevated ozone, so the shop adds fume extraction close to the weld, improves general ventilation and reviews welding parameters.

How to Control Ozone Exposure

1. Use local exhaust ventilation at welding stations and UV sources.
2. Enclose or shield UV lamps and ozone-generating equipment.
3. Lock out ozone generators before people enter treated areas, and ventilate before re-entry.
4. Monitor ozone levels where generators or UV processes are used.
5. Provide respiratory protection when engineering controls aren't enough.

Related Terms

• Ultraviolet (UV) Radiation Exposure
• Metal Fume Fever
• Local Exhaust Ventilation (LEV)
• Hot Work

Frequently Asked Questions: Ozone Exposure

Why does welding produce ozone?

The ultraviolet light from a welding arc splits oxygen molecules in the surrounding air, which recombine as ozone. Processes and metals that produce more UV, such as MIG and TIG welding on aluminum, generate more ozone.

Is ozone good for cleaning workplace air?

Ozone concentrations high enough to disinfect air or remove odors are also high enough to harm people, so ozone generators should only be used in unoccupied spaces with proper controls.

Does a dust mask protect against ozone?

No. Ozone is a gas, so particulate filters like N95s don't remove it. Engineering controls are preferred, and suitable cartridges or supplied air are needed if respirators are used.