Emissions of optical radiation during the treatment of glass workpieces by means of gas torches

Status:

completed 12/2010

Aims:

Gas torches are frequently used in glassworking for the heating of glass workpieces. The gas flame of these torches emits radiation in the optical (ultraviolet, visible and infrared) wavelength range. The workers may be exposed to optical radiation as a result. As already established in previous studies by the German Social Accident Insurance Institution for the energy, textile, electrical and media products sectors (BG ETEM) and by the Institute for Occupational Safety and Health of the German Social Accident Insurance (IFA), this radiation may exceed the permissible exposure limits.

The objective of this project was to use the results in order to identify suitable protective measures for glass treatment work involving gas torches by means of which the exposure limit values can be observed and hazards avoided. The results were also to support determining of the occupational UV radiation exposure in cases of occupational disease involving "skin cancer caused by UV radiation".

Activities/Methods:

The radiation emissions in the ultraviolet, visible and infrared ranges were measured systematically in the IFA's laboratory with regard to the torch type employed, the torch power, the gas type, the distance from the source of the radiation, the emission angle and the workpiece being treated. The radiation exposure of employees was also measured in a glass-blowing workshop under actual work and exposure conditions.

Results:

The following relationships were observed: the level of the optical radiation emissions depends upon the torch type and gas employed. Surprisingly, no relationship is observed between the radiation emission and the torch power. The reason for this has yet to be established. Nor is the emission level determined primarily by the emission angle. It is however dependent upon the distance from the radiation source, approximately in accordance with the inverse square law. When a workpiece is treated, the level of emissions and the radiation spectrum are influenced by shadow effects and by the temperature rise of the workpiece.

The occupational exposure limits on the hands, arms and face may be exceeded during the treatment of glass workpieces in a glass-blowing workshop. Some protective measures, such as the wearing of gloves, are not suitable, since the glass-blower would lose the sensitivity required during work.

The results of the project can be used during prevention activity and investigations into cases of formally recognized occupational disease, in order to support assessment of optical exposure during work involving gas torches. The need for extensive in-plant measurements can then be avoided. Recommendations can also be made for suitable protective measures. Some issues (see preceding paragraph) have however yet to be resolved.

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