Ozone

Classification

Classifications differ between sources. Japan's government GHS classification lists: Oxidizing gas, Category 1; Acute toxicity (inhalation), Category 1; Serious eye irritation, Category 2; Germ cell mutagenicity, Category 2; Reproductive toxicity, Category 2; STOT single exposure, Category 1 (respiratory system); STOT repeated exposure, Category 1 (lungs); Hazardous to the aquatic environment (acute), Category 1. Some EU registrants also classify ozone as corrosive to skin and eyes, so check your supplier's safety data sheet.

Hazard statements

• H270 May cause or intensify fire; oxidizer.
• H330 Fatal if inhaled.
• H319 Causes serious eye irritation.
• H341 Suspected of causing genetic defects.
• H361 Suspected of damaging fertility or the unborn child.
• H370 Causes damage to organs (respiratory system).
• H372 Causes damage to organs (lungs) through prolonged or repeated exposure.
• H400 Very toxic to aquatic life.

Key precautionary statements

• P220 Keep away from clothing and other combustible materials.
• P244 Keep valves and fittings free from oil and grease.
• P260 Do not breathe gas.
• P271 Use only outdoors or in a well-ventilated area.
• P284 Wear respiratory protection.
• P304+P340 IF INHALED: Remove person to fresh air and keep comfortable for breathing.
• P310 Immediately call a POISON CENTER or doctor.
• P403 Store in a well-ventilated place.

The OSHA PEL is 0.1 ppm as an 8-hour TWA (29 CFR 1910.1000 Table Z-1). NIOSH sets 0.1 ppm as a ceiling that should not be exceeded at any time. ACGIH scales its TLV to how hard people are working: 0.05 ppm for heavy work, 0.08 ppm for moderate work and 0.10 ppm for light work, with 0.20 ppm for any workload lasting 2 hours or less. Cal/OSHA adds a 0.3 ppm STEL to its 0.1 ppm TWA. The NIOSH IDLH is 5 ppm. No skin notation is assigned. State OSHA plans may set different limits.

• Appearance: Colorless to bluish gas
• Odor: Sharp, acrid odor
• Molecular weight: 48.0
• Boiling point: -169°F (-112°C)
• Freezing point: -315°F (-193°C)
• Flash point: Not flammable, but a powerful oxidizer
• Explosive limits: Not applicable
• Vapor pressure: Greater than 1 atm
• Relative gas density: 1.66 (heavier than air)
• Water solubility: 0.001% at 32°F (very slight)

Inhalation

Irritates the nose, throat and lungs, causing cough, chest tightness, shortness of breath and headache. Higher exposures can cause fluid in the lungs (pulmonary edema), which may appear hours after exposure.

Skin

The gas is not a major skin hazard at workplace levels. Liquefied ozone can cause severe irritation and burns.

Eyes

Irritates the eyes. Liquefied ozone can burn the eyes.

Ingestion

Not a likely route for a gas.

Target organs

Eyes, respiratory system

Long-term effects

Repeated exposure can damage the lungs and may contribute to chronic respiratory disease. NJDOH notes ozone is a possible mutagen and reproductive hazard, and there is limited animal evidence of lung cancer.

Where exposure happens

Ozone is generated on site for water and air treatment, bleaching and chemical manufacturing. It is also produced by electric arc processes, so it can be part of the exposure from welding fume, especially with gas-shielded arc welding.

Gloves

Ozone gas does not call for special gloves at normal workplace levels. Where liquefied ozone could be contacted, use insulated, non-absorbent gloves chosen with the supplier's help.

Eyes and face

Non-vented goggles where gas could irritate the eyes; a face shield with goggles for liquefied ozone.

Respiratory

Control ozone at the source with local exhaust ventilation and by enclosing generators. Up to 1 ppm, NIOSH lists chemical cartridge respirators with cartridges suitable for ozone or supplied-air respirators; up to 5 ppm, full-facepiece cartridge respirators, gas masks, supplied-air respirators or SCBA. Above 5 ppm or at unknown levels, use a pressure-demand full-facepiece SCBA. See respiratory protection.

Clothing

Ordinary work clothing for gas exposure. Keep oil, grease and combustible materials away from ozone equipment.

Ozone is unstable and is normally made where it is used rather than stored. Run generators in well-ventilated areas, check piping and destruct units for leaks, and use fixed gas detection in rooms with generators. Liquefied ozone is a severe explosion hazard when heated or disturbed.

Keep ozone systems clean and free of oil and grease. Train workers before they operate or service ozone equipment.

Keep away from

• Organic and combustible materials (wood, paper, oil)
• Alkenes, ethers and aromatic compounds such as benzene and aniline
• Strong acids and strong bases
• Other oxidizers such as peroxides, nitrates and chlorine

• Shut off the ozone generator and stop the flow if it is safe to do so.
• Evacuate the area and keep people out until levels are confirmed safe.
• Ventilate to disperse the gas.
• Remove ignition sources and combustible materials from the leak area.
• Responders need SCBA if levels may reach 5 ppm or are unknown.
• No ERG guide applies because ozone has no DOT shipping entry.

Suitable extinguishing media

• Ozone does not burn. Use media suited to the surrounding fire
• Water spray to cool exposed equipment and containers
• Dry chemical, carbon dioxide (CO₂) or alcohol-resistant foam

Special hazards

Ozone is a strong oxidizer that can start or intensify fires and may react explosively with combustible materials. Shut off ozone generation as a first step. Containers and equipment may burst in a fire. Firefighters should wear SCBA.

• OSHA Hazard Communication (29 CFR 1910.1200): Hazardous chemical; labels, safety data sheets and training required. See HazCom.
• OSHA Air Contaminants (29 CFR 1910.1000 Table Z-1): 0.1 ppm (0.2 mg/m³) TWA.
• OSHA Process Safety Management (29 CFR 1910.119 Appendix A): Threshold quantity 100 lb.
• CERCLA (40 CFR 302.4): Not listed as a hazardous substance.
• EPCRA Section 302 (40 CFR 355 Appendix A): Extremely hazardous substance, threshold planning quantity 100 lb, reportable quantity 100 lb.
• Clean Air Act: Not listed under the 112(r) Risk Management Program (40 CFR 68.130) and not a listed hazardous air pollutant. Ground-level ozone is regulated separately as an outdoor air quality pollutant.
• DOT (49 CFR 172.101): No UN number assigned.

• NIOSH Pocket Guide: Ozone
• OSHA Occupational Chemical Database: Ozone
• NITE (Japan) GHS classification: Ozone
• NJ Department of Health Hazardous Substance Fact Sheet: Ozone (Spanish edition)
• 40 CFR 355 Appendix A, EPCRA extremely hazardous substances
• OSHA 29 CFR 1910.119 Appendix A, highly hazardous chemicals