To make it possible to significantly reduce dust pollution in mechanised, advanced workings in steep-dipping seams, while maintaining conditions for personnel transport and material transportation.

The idea was to design a reliable and safe secondary ventilation exhausting system consisting of:

- an exhausting ventilation column located in the site and made of light materials so as to facilitate handling, being smooth to avoid build-ups of dust and approved for use underground.

- a fan with dust-extractor device in the primary ventilation system, the dust-extracting function being necessary to prevent the dust from being reintroduced into the main ventilation circuit.
The tests carried out on the complete dust-extraction system provide the following results:

- The complete dust-extraction system achieves the anticipated aeraulic performance (ie. 13.1 m{3}/s and 403 mm CE) and makes it possible to maintain an underground airflow of 10 m{3}/s with a maximum line extension of 700 m.

- The dust treatment is effective. In fact, in all cases the overall effective values exceeded 99%, and those for dusts liable to be inhaled are broadly better than 93% for a concentration of 2000 mg/m{3}, thus complying with the specification.

- In addition, filter clogging is reduced and self-cleaning seems to take place in a satisfactory manner.

- The average level of acoustic pressure at the intake louvre, with the soundproofing cover removed, is 101 dBA. The figure for points at a distance of 1 m from the outer edges is 93 dBA. These values may be reduced by approximately 3 dBA with the soundproofing covers in place.

As the complete dust-extraction system maintained the required aeraulic performance right through to the completion of cutting in the gateroad, the dust treatment system proved its effectiveness, even with regard to time-related developments, and with the build-up of dust in the conduits at the end of the advanced workings being relatively insignificant, we are in a position to report that the research has satisfied all of the requirements originally stipulated.
Research Programme

- to define and design an exhausting ventilation system with rigid, light and smooth conduits, with the fan and dust-extraction device located within the main ventilation system

- to design and implement measures or control and monitoring procedures ensuring the proper functioning of the installation as part of the firedamp prevention regime for the site

- to decide on the measures required to avoid or neutralise any build-ups of dust in the ventilation column.