Some jobs simultaneously generate more than one type of dust hazard, and a mixture of coarse and fine dust may be produced. In such circumstances achieving a satisfactory solution may require the use of multi-stage filtration - progressively filtering to finer levels.

Certain applications may even require the use of negative pressure filtration equipment in conjunction with polythene enclosures, to minimize the outbreak of airborne dust (see picture).

Envirogard has a wide range of filtration units for this type of application, capable of removing as much as 99.995% of the airborne dust, down to a particle size of 0.3 micron [to put this in perspective - 1 millimetre is 1,000 microns].