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Ozone - a Boon and a Plague

Published: 10th Oct 2002


Ozone protects and threatens us at the same time: 15 kilometres above us in the atmosphere ozone protects us against dangerous UV beams - on the surface the aggressive gas threatens our health.

High ozone concentrations, as they are registered during the summer months, can have an enormous effect on health. Ozone (O3) in the lower troposphere has a toxic effect on humans, animals and plants. Ozone that builds up under insulation in connection with exhaust fumes or sulphur dioxide leads to damage of the lungs, and not only temporarily. It causes inflammation of the respiratory tracts, leads to allergic reactions or worsens them and provokes asthma.

Ozone is not only useful in the atmosphere, but also in industries. It is used for processing purposes, disinfecting or sterilisation. Ozone is regarded as the safest way to process and keep water sterile. It is the most used oxidation means in Germany. The safe use of ozone makes high demands to systems, for example water process systems or air outlet systems. By installing fixed gas monitoring systems leakages due to worn system parts can be monitored around the clock.

Professional trade associations recommend the use of fixed gas monitoring systems for ozone systems with ozone production capacities of more than 2 g/h to ensure safety in operation areas.

Effect of ozone on humans
> 0,01503 ppm Humans smell the ozone, but the nose gets used to the odour very fast
> 0,03507 ppm First irritation of the eye conjunctiva
> 0,05010 ppm Headaches possible
> 0,08016 up to 0,1002 ppm Change of lung functions, especially during physical strains
> 0,10020 ppm Increasing number of white blood cells, immune system becomes inactive
> 0,12024 ppm Reduction of fitness
> 0,12024 up to 0,1503 ppm Increase in number of asthma attacks
> 0,20040 ppm Cough, chest pain and after 4 hours, alteration of hormones and enzymes
> 0,40080 ppm Inflammatory reaction of tissue
> 0,50100 ppm After 6 to 10 hours first damage to human chromosomes

Origin of ozone

For producing large ozone quantities the principle of a “stepped electrical discharge” is used, i.e. the oxygen molecules are divided into two oxygen atoms by means of a high voltage. These atoms react with oxygen molecules to form ozone (O3).

Most of the near ground ozone builds up during intensive sunlight out of nitric oxides; hydrocarbons intensify this process. These contaminants mainly come from vehicle emissions. In several chemical reactions the nitrogen dioxide (NO2) builds up from which the UV-beams from sunlight release one oxygen atom; this oxygen atom is combined with an oxygen molecule (O2) and ozone builds up:

NO2 + UV light -> NO + O; O + O2 ->O3

During good weather conditions the build up of ozone starts with rush-hour traffic. The highest concentrations can be measured in the afternoon. With airstreams these emissions or the ozone itself can be transported over huge distances to places which normally have clean air. Even indoors ozone can be built up by photocopiers, laser printers or heaters.

In Central Europe the ozone concentration near the ground increases by an average of 2% per year.

The TLV-value

The TLV (threshold limit value) is used for judging the ozone concentration at workplaces. The TLV indicates the maximum gas, vapour or suspended matter concentration a person can be exposed to during an 8 hour day or 40 hour working week that will not cause any damage to health. The threshold limit value (TLV) for ozone is set through government regulations; for Germany this value is set to 200 _g/m3 or 0.1 ppm.

Portable ozone warning instruments

With the help of a portable ozone detector dangers can reliably be detected. GfG offers one of the smallest ozone detectors available.

The MICRO III weighs only 75 g and is only a few centimetres tall. With its electrochemical sensor it can monitor ozone in a detection range between 0 and 1 ppm and reliably monitors the TLV. State-of-the-art processor technology allows the MICRO III to be operated for up to 9 months on a single Mignon AA-battery. The user can change the battery without needing any tools. A loud alarm and a 360º visible alarm light ensure safety.

For further info email

Published: 10th Oct 2002 in Health and Safety International

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