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Ozone Safety

General information about ozone safety

Download Safety Datasheet as pdf

Product/material Ozone
Molecular formula O3
Principal characteristics Oxidising gas – CAS no. 10028-15-6 / EG no. 233-069-2
Molecular weight 48.0
Production Corona discharge
Concentration Up to 18 % by weight in oxygen/oxygen-enriched air
Boiling point -111.0°C
Melting point -192.7°C
Solubility in water by weight (at 20°C) 570 mg/l
Vapour densitiy 1.6 (1 = air)
Flammability Non-flammable/vigorously supports combustion
Flash point Not applicable
Auto ignition temperature Not applicable

Appearance and odour

Ozone is colourless at all concentrations experienced in the industry. It has a pungent characteristics odour usually associated with electrical sparks. The odour is generally detectable by the human nose at concentrations of 0.02 and 0.05 ppm.

Fire/explosion and hazard data

Ozone is a powerful oxidising agent. Oxidation with ozone evolves more heat and usually ignites at a lower temperature than oxidising with oxygen. Ozone reacts with non-saturated organic compounds to produce ozonides, which are unstable and may decompose with explosive voilence. Ozone is an unstable gas that, at normal temperatures, decomposes to biatomic oxygen. At elevated temperatures and in presence of certain catalysts such as hydrogen, iron, copper and chromium, this decomposition may be explosive.

Reaction data

Conditions contributing to instability

Ozone spontanenously decomposes under all ordinary conditions, so that is not normally encountered except in the immidiate vicinity of its production. Decomposition is accelerated by contact with solid surfaces, by contact with chemical substances and by the effect of heat.


Ozone is a power oxidising agent and reacts with all oxidising materials, both organic and inorganic. Some reaction products are highly explosive.

Hazardous decomposition products


Health hazard data

Permissible exposure limits

The following limits are widely accepted (USA, Sweden, UK and other parts of Europe):

  • 8 hour per day/5 days per week (occupational exposure limit) – 0.1 ppm
  • 15 minutes (short term exposure limit) – 0.3 ppm

Toxicology of ozone

The acute and chronic effects of excessive exposure to ozone have been well investigated. Exposure to concentrations of ozone in excess of several tenths of a ppm sometime cause reports of discomfort in a small susceptible portion of the population. This can be in the form of headaches of dryness of the throat and mucous membranes of the eyes and nose following exposures of short duration. Repeated exposure to ozone at such concentrations at 24-hour intervals, however, caused no further increase in airway irritability. In fact after the first exposures, additional exposures to ozone had progressively lesser effects suggesting that tolerance may develop over time.

Ozone has been shown to be more injurious at concentrations exceeding 2.0ppm over several hours, such as experienced by gas shielded arv welders. The primary site of acute effects is the lung which is characterized by pulmonary congestion. This acute impact subsided in welders when exposures where reduced to less than 0.2ppm. Based on animal studies, exposure over 10 to 20ppm or an hour or less believed to be lethal in humans although there has never been a single recorded fatality attributed to ozone exposure in more than 100 years of commercial use. (Compare with this experience with Chlorine as which has claimed many victims in peacetime as well as during war).

With respect to long term or chronic toxicity, ozone is a radiomimetic agent, i.e. the effects of long term exposure to excessive ozone exhibits the same affects as excessive exposure to sunlight. These effects are drying of the dermal surfaces and general ageing of exposed tissues. Ozone is not generally regarded or suspected of being a human carcinogen, neither does in exhibit tertogenic or mutagenic properties.

In the event of an ozone leak:

  • Ventilate the area
  • Immediately switch the ozone generator off
  • Stop the flow of ozonated water
  • Where high levels of ozone are experienced (in excess of 0.1ppm) all personnel should vacate the affected area until it has been thoroughly ventilated
  • When ozone levels in excess of 0.3ppm are present, or when personnel are required to work in restricted spaces or tanks, where ozone my be present, only persons wearing suitable breathing apparatus should be allowed in the area and the appropriate safe working practices for confined areas should be applied

Destruction of waste ozone gas

It is accepted practice, and required by statute in some jurisdictions, that Ozone gas should not be released into the atmosphere but should be destroyed using an approved ozone destruction method. (Catalytic, thermal, or absorption).

Safe handling of waste ozone gas

All potential outlets of ozone gas into the occupied areas or external atmosphere should be identified.

  1. All routine operational releases of ozone to the occupied areas or external atmosphere should be contained and passed through an ozone destruction system (as above)
  2. All occupied areas where ozone is generated or applied should be provide with an effective ventilation system commensurate with the rate of ozone production and other risk factors
  3. Where ozone is applied to liquids It is important to consider that ozone will escape from solutions under most conditions. Precautions include: ensuring that all vessels containing ozonated liquids are air-tight or under negative pressure to prevent escape of ozone. Any vents where ozone might escape should be connected to an ozone destruction system. Where ozonated liquids, such as used rinse water, are discharged this should be via close pipe work to close drains

Safety measures

  • Eye exposure – If ozone gets into the eyes, wash immediately with large amount of water, lifting the upper and lower eye lids occasionally. Seek medical attention as soon as possible
  • Breathing – If a person breathes in large amounts of ozone, move the person into warm uncontaminated air at once. If the person has stopped breathing, perform artificial respiration. If breathing is difficult, properly trained personnel may assist by administering breathing oxygen. Keep the affected person warm and at rest. Seek medical attention as soon as possible.
  • Rescue – Move the affected person to safety. If the person is unconscious, notify somebody else and put into effect the established emergency procedures. Do not enter the affected area without assistance or against the advice of the recommended safety procedures as they may apply at each facility

Mellifiq, or any of its subsidiaries shall not be liable for any loss or damage of any nature whatsoever, however arising, relating to the use or handling of ozone or statements contained in or omitted from this document.