The "in-use" provision applies to all research labs, not just academic labs.  It is not an "exception" just for "academic" labs.  However, the interpretation of "in-use" is that the cylinder of oxidizing or fuel gas is physically connected to an analytical device (e.g., a gas chromatograph or flame photometer), a manifold, or the like.  When not "in-use" (e.g., the single standby cylinder of flammable gas kept available to allow a quick change out) the protective cap must be on the standby cylinder (thus necessitating removal of the pressure/flow regulator); and the cylinder properly secured to prevent tip over. 

This "standby" provision is NOT consistent with use of a research laboratory as a "storage" area for many capped cylinders.  The 20-ft rule and or non-combustible barrier would apply if a reasonable person perceives that the lab is used for "storage," - a function that should generally be limited to one or a few specially designed/equipped rooms in a building.  I will attempt to find more specific information other than simply firm recollections based on numerous Q&A over many years.

NFPA 45 (approx title: fire safety for laboratories) is probably a good source. However, I do not have direct access to the document. 

David Haugen (retired)
Argonne National Laboratory

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From: "Don Abramowitz" <dabramow**At_Symbol_Here**BRYNMAWR.EDU>
To: DCHAS-L**At_Symbol_Here**MED.CORNELL.EDU
Sent: Tuesday, January 17, 2012 12:42:30 PM
Subject: Re: [DCHAS-L] Cylinder question