Respiratory protection against ozone

Status:

completed 09/1995

Aims:

Increased environmental ozone concentrations in summer represent a medically proven health strain especially for outdoor workers, for instance in the construction sector and in forestry. The eyes and the respiratory tract are particularly affected by exposure to high ozone concentrations. Unless technical and organisational measures do not offer reliable protection against ozone, it is necessary to make use of suitable respiratory protection. The investigation was aimed to check the efficiency of various filtering respiratory protective devices against ozone. On account of the results, requirements were to be defined in a co-operative approach by the BIA, manufacturers and the BG expert committee for personal protective equipment. Besides, the development of instruments and test bases were aimed at to help the user select suitable and positively tested respiratory equipment.

Activities/Methods:

Orientation tests were carried out to determine the filtering performance of different types of filters with respect to ozone: treated and untreated activated charcoal, Hopcalite, catalytic filters and particle filters made of fibre glass and electrostatic non-vovens. The tests were conducted at a medium ozone concentration of 0.7 PPM using both individual filters (volume flow 30 l/min) and powered respirators with helmets (volume flow 160 l/min). The inhaled ozone concentration as a function of time was considered the evaluation criteria.

Results:

The comparison showed that only activated charcoal and Hopcalite filters with a filtering performance of >99% offer reliable protection against ozone. This high performance is supposed to be due to the disintegration of ozone at the surface of the adsorbing material. The filtering efficiency of the tested catalytic filters comes to 88%. Fibre glass filters with an immediate breakthrough turned out to be inefficient. Electrostatic filter materials made proof of a good filtering performance in the beginning, which decreases quickly, however. Because of their favourable microclimate, low weight and reduced breathing resistance, powered respirators with helmets and hoods proved to be a particularly good solution, not least because they protect eyes and respiratory tract at the same time. In any case, the use of respiratory protective equipment is governed by special provisions.

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