Our common CRAC Units (Cooling, Refrigeration and A/C) for data centers only cool the air directly from the data center and back into the data center.

Do these need to be shutdown with the use of a total-flooding clean agent system? 

If the CRAC unit is only exchanging air within the same space then I'm not sure what harm it would do if it's running during or after clean agent discharge. I'm curious if I'm off the mark here, thanks!

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NFPA 2001 requires a safety factor under sections 5.4.2.3 through 5.4.2.5 for clean agent extinguishing concentrations.

What is the difference between the "design concentration" listed in Table A.5.4.2.2(b) (2015 edition) and this minimum extinguishing concentration (the minimum extinguishing concentration MEC x applied safety factor)?

In some cases the design concentrations are higher than the MEC x safety factor - is there a proper one to be using under NFPA 2001? Sorry if the question is basic - I've always just used the design concentrations.

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