I’m curious as to what the consensus view is on what is meant by the term “free-air” in the reference below:

(11) 

Where used for communications, wiring from switches or sensors that is supervised or protected as required by 517.30(C)(3) of NFPA 70, National Electrical Code, for life safety and critical branches circuits in which protection is any of the following types: 

(a) Conduit

(b) Free air

(c) Wire

(d) Cable tray

(e) Raceways

I have seen this defined as wireless communications, as well as cable run not in a cable tray or raceway.  Thoughts?

Free Air in the electrical sense is dealing with the protection of the wire within it's assembly. Free Air is typically looked at as the separation of each conductor within an assembly by a free air space of at least 100% the size of the conductor. The space allows for heat dissipation and protection of the conductor.
 

I found this in the 2011 report on comments (for the 2012 revision of NFPA 99), this was where the term free air made it's way into this section of the code so far as I can tell.  There is a mention of free air and the committee statement mentions allowing for new technologies that are not wire based.  However, it seems like subparagraph 12 speaks to this primarily. 

Is it possible that the term "free air" wasn't meant to refer to how it is used throughout the rest of NEC?  If so it was a confusing choice to put that term within the same paragraph as a reference from NEC.

Submitter: Jim Lucas, Tri-Tech Medical Inc.

Comment on Proposal No: 99-260

Recommendation: Revise text to read as follows:

Wiring from switches or sensors that is supervised or protected as required

by Alarm electrical components with power requirements above 24 volts shall

comply with Section 517.30(C)(3) of NFPA 70, National Electric Code, for

emergency system circuits.

Substantiation: The goal is to provide continuous surveillance that is

supervised or protected. Current verbage restricts new technologies such as

optical data transfer, (ie. fiber optics or laser), Ethernet, and electromagnetic

(ie. wireless).

Committee Meeting Action: Accept in Principle

Revise text to read as follows:

(9) Power for master, and area alarms, sensors, and switches, from the life

safety branch of the emergency electrical system as described in Chapter 6.

(11) Where used for communications, wiring from switches or sensors that is

supervised or protected as required by Section 517.30(C)(3) of NFPA 70,

National Electrical Code, for life safety and critical branches circuits in which

protection is any of the following types: conduit, free air, wire, cable tray, or

raceways.

(12) Communication devices that do not use electrical wiring for signal

transmission will be supervised such that failure of communication shall

initiate an alarm.

Renumber existing paragraphs:

(12) to (13)

(13) to (14)

(14) to (15)

Committee Statement: This change will permit new technologies that are not

wire based.

Number Eligible to Vote: 22

Ballot Results: Affirmative: 20

Ballot Not Returned: 2 McManus, J., Shoemaker, E.