Separation of E-Cylinders

Is there a standard that notes that full e-cylinders need to be separated from empty cylinders?  

I searched the 2005 NFPA 99 Health Care Facilities Handbook, specifically Section 9.4 Cylinder and Container Storage Requirements, and could find nothing requiring full e-cylinders to be separated from empty cylinders. However, I believe it is common and accepted practice to separate and/or identify empty cylinders from full cylinders of any size.  I believe the main reason for separating the full and empty cylinders and designating with signage, is so that someone doesn’t accidently grab an empty cylinder in lieu of a full one, especially during an emergency situation.  In previous surveys, TJC has noted that there should be one cylinder rack for Full tanks and one for Empty tanks, with signage indicating which rack is for Full tanks and which one is for Empty tanks, so that full and empty tanks are not mixed.