Conversation Notes between William Creed, Engineered Systems, Woburn, MA, and John Eyraud and Karen Capwell, ERG regarding the most common characteristics of industrial ventilation systems for reducing silica exposures. 

		MEMORANDUM

To:	Robert Burt, Robert Stone, Bob Blicksilver OSHA	 
From:	John Eyraud and Chet Fenton, ERG
Date:	May 28, 2014
--------------------------------------------------------------------------------
Subject:	Conversation Notes Regarding Average Ventilation Operating Costs

Discussion with Bill Creed, Engineered Systems, Inc., Woburn, MA and John Eyraud and Karen Capwell, May 23, 2014.

The determination of whether air would be recirculated is based on the interplay of the International Mechanical Code (IMC) and the International Energy Conservation Code. The IMC, however, would generally not be recommending recirculation of air in dusty or other hazardous environments. The International Energy Conservation Code would tend to encourage more recycling of air but that would probably not dominate the design considerations. The IMC generally requires the exhaust of dust. 

Axial fans should be used in the design, not centrifugal fans. An average fan efficiency estimate should be built into the number. 

For cost estimation purposes, he has not seen facilities with 30 inches of static pressure. For most installations he is familiar with, 4 to 10 inches of static pressure is sufficient. In the supply calculations, it is appropriate to use 1 inch to 3 or 4 inches of static pressure. 

In his industrial work, he does not normally design cooling systems. Unless the product characteristics require cooling air inputs, cooling is not normally being provided. He has not worked outside New England, however. He could not suggest an average range for ventilation operating costs. 


