ected to the most obvious dust generating areas, such as con-
veyors, transfer points and crusher discharges. This method

was unsatisfactory as far as current emission standards are
conterned, but did reduce dust levels inside the plant con-
siderably and to less than 10 MPPCF average. Problems with duct
plugging, fan blade overloading, and excessive maintenance were
common, particularly in periods of cool weather. In the early
1970's studies were commenced to improve the dust control by
engineered redesign of ductwork and enclosures, and some further
improvement was achieved. With the introduction of proposed
emission objectives for the mining industry and new asbestos

air standards it became quite apparent that existing dust control
systems would not be able to comply with the future requirements,
and installation of new equipment was chosen as the desired course
of action. It was also decided that at the same time a more
effective inside dust control design would be instituted. We
should note that as well as the current MPPCF TLV, asbestos
operations also must meet a fiber per millilitre TLV, in effect

a standard defining allowable fibre levels in the total dust

concentration.

The first stage of improvement was to install building
insulation and a wall across the pan feeder bin and equip it with
a flapped opening only at the base to allow ore passage to the
jaw crusher. Prior to this a rubber flap had existed from the
top of the building to the front of the pan feeder bin, and
every time an ore truck backed up to discharge its load a con-
centrated surge of displaced air and dust was pushed into the
building interior, completely defeating exhaust hood systems.

The new wall also tended to reduce heat loss to the outside.