[Limits in the use of cobalt filters for protection against infrared radiation].

Cobaltic filters are widely used to protect eyes against infrared radiation. They absorb a greater part of the incident on the filter radiation. The radiation absorbed by the filter enhances its temperature and thus increases infrared radiation regenerated by the filter. This paper describes the study of the effect of Tk cobaltic filter exposed to infrared radiation in the range from 500 W/m2 to 3000 W/m2 on the quantity of infrared radiation regenerated by the filter. The results of the study show the increase in the filter temperature depending on the filter irradiance and the exposure duration. In the case of the filter exposure to irradiance of 3000 W/m2 lasting longer than 10 min the filter temperature may go over 120 degrees C. Radiation regenerated by such a filter reaches about 1250 which exceeds the safe value for ocular exposure. On the basis of the results obtained the conditions for protecting eyes against infrared radiation by cobaltic filters are described.