UV Cleaning & Modifying

What is Ozone

What is Ozone

Ozone (O3) was discovered by Dutch scientist Martinus Van Marum in 1785.In 1840, a German chemist named it Ozon after the Greek word for "smell" because of its characteristic odor.

It is an allotrope of oxygen consisting of three oxygen atoms, and is the second most oxidizing gas after fluorine, making it highly poisonous and harmful to the human body in high concentrations. On the other hand, it has been used for a long time because it is environmentally friendly as it naturally decomposes back to oxygen. UV ozone is used not only for surface cleaning and modification, but also for sterilization, bleaching, and deodorization.

Mechanism of ozone generation by UV irradiation

When oxygen molecules (O2) are irradiated with ultraviolet light with a wavelength shorter than 240 nm, a decomposition reaction called dissociation occurs, separating them into two oxygen atoms (O).

UV ozone cleaning and modification equipment using low-pressure mercury lamps as the light source is mainly irradiated with UV light at wavelengths of 184.9 nm and 253.7 nm, because the energy of the 184.9 nm UV light is 647 kJ/mol, which is greater than the binding energy of 490 kJ/mol of oxygen molecules.

O2　+　h$ν$　→　O　＋　O

The dissociated oxygen atoms (O) then react with other oxygen molecules (O2) to produce ozone.

O　＋　O2　→　O3

Cleaning surface modification by ozone

UV irradiation in the general atmosphere increases the concentration of reactive oxygen, including ozone, directly under the UV lamps. The following phenomena occur as a cleaning leaf surface modification effect at that time.

Conditions are created that facilitate oxidation of the surface of the material to be treated.

1. Conditions are created that facilitate oxidation of the surface of the material to be treated.
2. Conditions are created that facilitate the reaction of organic contaminants on the surface of the material to be treated with reactive oxygen.

These two effects can further enhance the cleaning surface modification capability of UV light alone.

Ozone Effects on the Body

Ozone has an unstable structure and is easily converted back to oxygen through self-decomposition, but depending on its concentration, it is toxic to the human body. Therefore, although there are no laws or regulations that directly regulate the installation or operation of ozone-generating equipment, safety measures for the work environment and equipment are essential.

It is also important to be aware of the hazards involved in installing and working with equipment that generates ozone.

Work Environment Standards

The Japan Society for Occupational Health (JSOH: Japan Society for Occupational Health) has set a recommended standard of 0.1 ppm (0.2 g/m3) as the allowable concentration of ozone (in 2021).

It is considered that if exposure concentrations are below this level for those who work 8 hours a day (about 40 hours a week) in jobs with low physical load, there will be no negative effects on the health of almost all workers.

In addition, the American Conference of Governmental Industrial Hygienists (ACGIH) has established a 0.1 ppm TLV-TWA value (1993-1994) as a U.S. standard.

TLV ： Threshold Limit Value
TWA：Time Weighted Average Concentration

Indoor Environment Standards

As an index of ozone concentration, the Japan Air Cleaning Association (JACA) reports that the maximum allowable concentration of indoor gases from ozone generating devices is 0.1 ppm, and the average is 0.05 ppm.

Ozone Effects on the Body

Ozone concentration Effect
0.01～0.02ppm Slight odor can be smelled (eventually acclimated)
0.1ppm Obvious odor and irritation of the nose and throat (allowable concentration for occupational health)
0.2～0.5ppm Visual loss after 3-6 hours of exposure to this concentration of ozone
0.5ppm Obviously feel irritation in the upper airway
1～2ppm After 2 hours of exposure, headache, chest pain, thirst in the upper airway, and coughing occur, and repeated exposure results in chronic poisoning
5～10ppm Increased pulse rate, leading to pulmonary edema
15～20ppm Small animals die within 2 hours
50ppm Even humans can become life-threatening in an hour

For safe use of ozone

Ozone itself has a characteristic irritating odor, which can be detected by sensitive people at concentrations as low as 0.01 ppm, so it is recommended that measures such as ventilation be taken if an odor is detected.

Our equipment is designed with a negative pressure structure that also cools the lamps, so there is no risk of exposure to ozone during normal use. In work environments where ozone concentrations are high, we can provide ozone decomposition equipment if an ozone exhaust connection is not possible or if there is no exhaust facility.

We also provide ozone concentration measurement by our sales engineers who are certified ozone safety managers, as well as ozone decomposition equipment by itself. If you have any concerns about ozone exhaust, please feel free to contact us.

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