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Pilot studies of CEN protocols for evaluating the emission of airborne hazardous substances from machines


The main aims of this project are:
a) to evolve the necessary methodology for Part 2 of EN 1093 (Tracer Method);
b) to improve the emission rate measurements for all emitted particles especially the larger ones which dominate the inhalable fraction using the Test Bench Method as specified in Part 3 of EN 1093;
c) to evaluate the reproducibility of the improved methods by means of preliminary tests using firstly a reference pollutant source, and secondly a simple machine (a cutting machine for aerosols; a cleaning machine for gases and vapours).
Suitable test rigs were commissioned and tested in 5 partner laboratories, with particular attention being paid to the mixing of pollutant in the measurement duct. A suitable reference dust source chosen and validated. The effect of a range of experimental parameters on the measured emission rate was investigated, and it was found that the air velocity in the cabin was the major source of bias in the emission rate results. Tests on the efficiency of the test cabin for measuring the emission rates of particles from the reference dust source were carried out in 7 laboratories. The efficiency was found to be dependent upon the size of the emitted particles, falling to 45 % for particles of mass median aerodynamic diameter (mmad) 75 µm. This efficiency was increased to 75 % by including the particles deposited on the internal walls of the test bench. Overall reproducibility was found to be 10%. Measurements of emission rate from a real simple circular saw machine cutting three different materials gave variabilities between 14 and 17 % when cutting three different materials.. Biases were dependent upon the materials being cut ranging from 0 to 40%. These were reduced to <10 % when particle wall losses were included. A list of improvements for EN-1093-3 was produced based on the findings from the work, for submission to CEN/TC114/WG15.

Suitable test rooms and gas monitoring equipment were commissioned and validated in 3 partner laboratories. Two reference gas sources were produced and validated and the choice and most suitable method of injection of tracer gas were made. The location of the sampling points were chosen from work with the reference gas sources, and a draft protocol produced. The accuracy of the method was investigated from measurements of the emission rate of solvent from a parts cleaning machine. The overall variability in the results was 11 % with the mean bias in the range -10 to +5 %. A draft protocol for EN 1093-2 was produced for submission to CEN/TC114/WG15. The use of tracer gas to predict the emission rates of particles showed very limited success, with biases > 50% for particles of mmad of 6 µm. The injection of tracer gas into the test bench was shown to give equivalent results to the those obtained from dust sampling ,and this led to the option for EN 1093-3 of using the tracer gas technique and sampling at just one central point. The feasibility of using tracer particles for predicting the emission rates of particles from machines was studied. The use of size graded batches of a pure fluorescent material was found to show promise, with preliminary results giving biases < 20 % for particles as large as 105 µm mmad.
This project involves a number of pilot studies to resolve technical difficulties with two of the test methods recommended in European B-Standard EN 1093 "Safety of machinery - Evaluation of the emission of airborne hazardous substances". This standard includes separate test methods for assessing both the emission of pollutants from machines and the performance of the pollution control systems integrated into machines. In Part 2 (Tracer Method), further development of the methodology is required.In Part 3 (Test Bench Method), doubt has been expressed about the validity and accuracy of the recommended method, especially for particulate pollutants.

There are two main objectives of this project.1) To resolve the technical difficulties of the method for the measurement of the emission rate as specified Part 3, and to evolve the necessary methodology for Part 2.2) To evaluate the reproducibility of the improved methods by means of preliminary tests using firstly, a reference pollutant source, and secondly a simple machine(cutting machine for aerosols, gluing machine for gases and vapours).

Work programme: To meet these objectives the following work programme will be carried out:1) development of reference pollutant sources (both dust and gas) for use in the tests;2) investigation of the parameters which affect the results of the both the existing Test Bench method and the proposed Tracer Gas method;3) use the results from 2) to revise and improve the protocols of both methods;4) carry out preliminary tests of revised protocol using reference pollutant source to determine there reducibility of the two methods;5) carry out preliminary tests with simple cutting and gluing machines to highlight any problems with the methods associated with the operation of machines, and to provide estimates of the accuracy of the final methods.

State of progress The necessary equipment has been procured and commissioned and a statistically sound experimental protocol has been produced. For the Test Bench part of the project, existing test cabins and an existing wind tunnel have been modified for the project. The airflow characteristics of all facilities have been evaluated. Tracer gas concentrations were very non-uniform; various methods of introducing mixing into the cabin have been tried. A reference dust source has been chosen, and comparisons were made to ensure consistency between the laboratories. For the Tracer Gas part of the project, test rooms suitable for the programme of experiments were selected and their ventilation characteristics (air exchange efficiency, ventilation efficiency, local "age" of air) have been determined. Two reference gas sources (a point source and a planar source) have been developed and tested. For both parts of the project, the parameters that arethought to effect the emission rate measurements are now being investigated.

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University of Birmingham
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University West Road Edgbaston
B15 2TT Birmingham
United Kingdom

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Participants (7)