OZONE

Ozone
CAS 10028-15-6

O₃

Colorless to bluish gas
bp -112 °C, mp -193 °C
Almost insoluble in water (0.00003 g/100 mL at 20 °C)

Pungent odor, detectable at 0.01 to 0.04 ppm; sharp disagreeable odor at 1 ppm

1.65 (air = 1.0)

LC₅₀ inhal (rat) 4.8 ppm (4 h)

PEL (OSHA) 0.1 ppm (0.2 mg/m³)

TLV-TWA (ACGIH) 0.1 ppm (0.2 mg/m³)

STEL (ACGIH) 0.3 ppm (0.6 mg/m³)

Extremely irritating to the eyes and respiratory tract; high acute toxicity. Reacts violently with many oxidizable organic and inorganic substances; may form shock-sensitive and highly explosive reaction products.

Ozone is a highly toxic gas that is extremely irritating to the eyes, mucous membranes, and respiratory tract. The characteristic odor of ozone can be detected below the permissible exposure limit, and this compound is therefore regarded to have adequate warning properties. However, at higher concentrations the ability to smell ozone may decrease. Inhalation of 1 ppm ozone may cause headaches and irritation of the upper and lower respiratory tract. The first symptoms of exposure include irritation of the eyes, dryness of throat, and coughing; these symptoms disappear after exposure ceases. Exposure at higher levels may lead to lacrimation, vomiting, upset stomach, labored breathing, lowering of pulse rate and blood pressure, lung congestion, tightness in the chest, and pulmonary edema, which can be fatal. Exposure to 100 ppm of ozone for 1 hour can be lethal to humans.

Animal studies indicate that chronic exposure to ozone may result in pulmonary damage, leading to chronic lung impairment. Continual daily exposure to ozone can cause premature aging.

Ozone by itself is not flammable. Liquid ozone and concentrated solutions are extremely hazardous and can explode on warming or when shocked.

Ozone is a powerful oxidant and can react explosively with readily oxidizable substances and reducing agents. Explosions can occur when ozone is exposed to bromine, hydrogen bromide, hydrogen iodide, nitrogen oxides, lithium aluminum hydride, metal hydrides, hydrazine, alkyl metals, stilbene, ammonia, arsine, and phosphine. Ozone reacts with alkenes and other unsaturated organic compounds to form ozonides, many of which are highly unstable and explosive. Ozone combines with many aromatic compounds and ethers to form shock-sensitive and explosive products.

Because of its high degree of acute toxicity, ozone should be handled in the laboratory using the "basic prudent practices" described in Chapter 5.C, supplemented by the additional precautions for work with compounds of high toxicity (Chapter 5.D) and high reactivity (Chapter 5.G). In particular, work with ozone should be conducted in a fume hood to prevent exposure by inhalation. Ozone is usually produced in the laboratory with a ozone generator, and care should be taken to ensure adequate ventilation in the area where the ozone generation equipment is located. Because of the possibility of the generation of explosive ozonides, ozonolysis reactions should always be conducted in a fume hood behind a safety shield.

An ozone leak can be easily detected by its characteristic pungent odor. If a large amount of ozone is inhaled, move the person to fresh air and seek medical attention at once. In the event of eye contact, promptly wash eyes with copious amounts of water for 15 min (lifting upper and lower lids occasionally) and obtain medical attention.

Respiratory protection may be necessary in the event of an accidental release of ozone.

Ozone is usually produced on demand from a laboratory ozone generator, and a procedure for the treatment of excess ozone should be included in the experimental plan. Small to moderate amounts of excess ozone can be vented to the fume hood or other exhaust system. When large amounts of excess ozone are anticipated, the excess gas should be passed through a series of traps containing a 1 to 2% solution of potassium iodide or other reducing agent before venting to the fume hood.

The information in this LCSS has been compiled by a committee of the National Research Council from literature sources and Material Safety Data Sheets and is believed to be accurate as of July 1994. This summary is intended for use by trained laboratory personnel in conjunction with the NRC report Prudent Practices in the Laboratory: Handling and Disposal of Chemicals. This LCSS presents a concise summary of safety information that should be adequate for most laboratory uses of the title substance, but in some cases it may be advisable to consult more comprehensive references. This information should not be used as a guide to the nonlaboratory use of this chemical.

Copyright 1995 National Academy of Sciences. All rights reserved.