Elaboration of generally valid respiratory characteristic curves for a process to determine the serviceable life of protective breathing filters at the work place with the help of a newly developed mobile testing device

Status:

completed 06/1998

Aims:

Protective breathing filters have a limited serviceable life which, where exceeded, results in exposure. Filter breathing equipment is therefore not permitted with non-detectable dangerous substances (smell/taste). The theoretical determination of the serviceable life or permitted period of use requires very large safety margins which lead to lower filter utilisation. A mobile testing device developed by the research institute enables the actual serviceable life of the filter to be determined at the work place. The control of the testing device requires realistic characteristic breathing curves. Goal: determining statistically safeguarded breathing curves with sufficiently general characteristic for control of the filter testing device

Activities/Methods:

Determining respiration data and characteristic curves from approximately 40 suitable persons (fire fighters) with defined ergometric stress; statistical processing; validation of the results in the field test (fire brigade training ground)

Results:

The statistical evaluation (clustering) of the data acquired under standardised conditions resulted in a large variance in breathing curve types. With nominally equal stress the pulmocardinal parameters and/or the respiratory sequence differ considerably between the ergometer and the training ground (with heavy protective clothing), so that the intended validation of the characteristic breathing curves acquired through the ergometer was abandoned as a result of the field test; a hypothetical explanation will be provided. Conclusions: a new approach for obtaining control curves for the filter testing device must be based on appropriate field measurement values and an improved clustering method, the determining of different respiratory patterns with the ergometer and in practice should be taken into account in the standardisation of the filter test and in preventative occupational medicine.

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