Air Filters - Recommend Porosity (Above 200 HP)
	Wastewater Treatment - Selection of air filters depends on the downstream fine bubble diffusers. These manufacturers recommend the following two stage filter be used.          Coarse outer first stage - 93% removal efficiecy on 10 micron          Fine secondary filter - 99.5% removal effieciency on 10 micron Size filters for a face velocity not exceeding 575 feet/minute at peak air flow. Industrial air process requirements vary widely from pharmaceutical/food grade applications requiring very clean air, to other process applications that have no requirement. In the latter case, only the compressor, per se, needs protection, and for this, a single-stage filter of 93% removal efficiency on 10 micron is adequate.