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Ozone exhaust

A corona treater typically has corona discharge take place in the atmospheric pressure, which results in the generation of ozone and nitrogen oxide (NOx) in the treating station. These substances are harmful to the human body and also have a harmful effect, such as corrosion, on machines around the corona treater. Measures therefore need to be taken to prevent leakage of ozone and NOx from the treating station. A common treating station has an exhaust duct entrance, through which air inside the station is exhausted. Installation of pipes for exhausting ozone, and an exhaust blower, allows the station to discharge the ozone and NOx outside the building. The inside of the exhaust blower also becomes highly acidic during operation, so acid-proof coating of its inner surface or use of a stainless blower is recommended.

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Ozone hazard

Ozone has toxicity. Ozone fumes can be smelled when the level is 0.01-0.02 ppm. About 0.1 ppm of ozone causes irritation of the nose and throat, and 0.2-0.5 ppm weakens eyesight, weakens the reduction of responsiveness of the pupils, and/or triggers eye irritation. Ozone at 0.4-0.5 ppm causes irritation of the upper air passage, and 0.6-0.8 ppm results in chest pain, coughing and/or decreased lung function and lung diffusing capacity. Fatigue, headache, heaviness of the head and/or change in respiratory functioning results at 1-2 ppm. An ozone level at 5-10 ppm triggers breathing difficulty, malaise and/or increased breathing rate. At 15-20 ppm, a small animal will die within two hours and a human will acquire pulmonary edema, and a 50-ppm or higher level of ozone threatens human life. Symptoms of acute ozone poisoning include nasal inflammation, irritating cough, dry respiratory passage, chest tightness, heaviness of the head, headache, dizziness, nausea, fatigue and falls in blood pressure. Severe cases result in pulmonary edema and lung bleeding, and even decline of cardiac function, falling body temperature and spasms, which can result in death.

Permissible ozone concentration

Concentration in work environment

The Permissible Concentration Committee of the Japan Society for Occupational Health stipulated in 1985 that permissible concentration of ozone in the work environment is 0.1 ppm. The committee deems that there will be no impact on the health of almost any worker if the arithmetic mean value of exposure concentration is 0.1 ppm or below for not especially strenuous work at eight hours/day, 40 hours/week. Exposure concentration means concentration of a substance in the air inhaled by a worker not wearing a protective mask. It is deemed desirable that the concentration does not exceed a level 1.5 times higher than its 15-minute average.

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