PDFWAC 296-99-060
How must filter collectors be installed?
(1) You must ensure that, on a pneumatic dust collection system, each fabric dust filter collector has a monitoring device that will show a pressure drop across the surface of its filter.
(2) You must ensure that each filter collector installed after March 30, 1988, is:
(a) Located outside the facility; or
(b) When located inside the facility, protected by an explosion suppression system; or
(c) Isolated by a structure with at least a one hour fire-resistance rating:
(i) Next to an exterior wall;
(ii) Vented to the outside; and
(iii) The vent and ductwork must resist rupture from intense heat.