When I opened a neutral splice in a fluorescent fixture once, that was still energized it felt like I was kicked in the head by a horse!
410.130(G) Disconnecting Means.
(1) General. In indoor locations other than dwellings and associated accessory structures, fluorescent luminaires that utilize double-ended lamps and contain ballast(s) that can be serviced in place shall have a disconnecting means either internal or external to each luminaire. For existing installed luminaires without disconnecting means, at the time a ballast is replaced, a disconnecting means shall be installed. The line side terminals of the disconnecting means shall be guarded.
Exceptions are open for discussion. Also what is different about "dwellings and associated accessory structures"?
Reno; Don't forget that wonderful rule that ALL motors had to be the much more expensive energy efficient type. Even that monster 100 Hp motor on the fire pump that runs 15 minutes a year for testing...and hopefully never needs to run to control a fire! That's money that could have been better spent buying a better quality switchboard, etc.
Ahh ... an interesting detail, that fixtures used in homes need not have the disconnects.
Perhaps this is related to a)the ban on 277 lighting in homes and b)the documented deaths of electricians replacing 277 ballasts 'hot?'
As I've observed here before ... even lacking a NEMA standard on the disconnects, the entire issue would be decided if only ONE ballast maker - Advance - were to include the gizmos with their ballasts. Advance has a large enough market share that their choice would become the 'de facto' standard.
This "other than dwellings and associated accessory structures" wording goes back first to the Proposals for the 2005 NEC®. Back then, this 410.130(G) was numbered to fall into 410.79 and was ultimately designated as 410.79(G).
From the May 2004 ROP, Proposals 18-92 (Log #1780) from Craig Wellman and 18-93 (Log #3421) from Danny Liggett proposed this requirement, each with slightly different wordings.
The original wording in those Proposals was "other than dwellings and related/associated outbuildings".
For your question, a portion of the Substantiation to P18-92 (Log #1780) goes to the heart of your question: "In commercial, industrial, institutional and government facilities, it is often unsafe or impractical to turn off power to luminaires at the panelboard. Turning off the power may leave a room in the dark or may reduce illumination, which in some cases can/could create work related hazards for facility occupants. ..."
So, reading between the lines, the distinction seems to be that dwellings and associated accessory structures are exempted from this luminaire disconnect requirement because: • dwellings are not as large as those other occupancies to have as great a distance between panelboard and the luminaire being serviced • rooms in dwellings generally have windows (for fire egress) that allow natural illumination whereas those other occupancies more typically include rooms without windows