What does osi stand for?

As in, "a 16 osi blower delivers 400 cfm of air through a piping system..."

I know that cfm is a way of writing cubic feet per minute. PSI is pounds per square inch.

Building systems to move gases and liquids around safely has really had me stumped till now, especially when dealing with HVAC. I'm not familiar with some of these units.

I think OSI is ounce-force per square inch, and it is related to PSI by a factor of 16. That is 1 PS1 = 1 (pound)*(inch)-2 = 16 (ounce)*(inch)-2= 16 OSI

I suspect it is a unit that got invented just for rating blower pressure because quoting the numbers in PSI made them seem small.  E.g. 6 OSI = 0.375 PSI, but it looks/sounds more impressive to quote 6 OSI, rather than 0.375 PSI.
Vorenus (author)  Jack A Lopez5 years ago
Thank you.