What defines the limits of a classified location?

[retire09]

If you have a door separating a repair garage from the office area; what is required of the door to maintain some separation between the classified and unclassified locations?
Is just a self closing door with a tight seal adequate?

 

[rbalex]

This is a tough one. I've said before that classification can't usually be determined from the NEC itself - except for installations subject to Articles 511 to 516. Where they apply, those Articles basically preempt other classification documents .

In this case, Section 511.3(E)(1) would be relevant but it doesn't answer your question directly unless you use ventilation or positive pressure. Unfortunately, a "... self closing door with a tight seal ..." still isn't a wall or partition.

Even more general classification standards, such as NFPA 497 or API RP 500, wouldn't recognize a "... self closing door with a tight seal ..." either; however, they would typically create the envelope based on the source of release. The problem with Article 511 is the "source" is the "floor area" described in 511.3(C)(1) or 511(D)(1) and the office would simply be treated as a extension.

That said, I personally would go for ventilation. It isn't that onerous.

 

[greenspark1]

511.3(C)(1) contains good guidance for major repair garages. Like rbalex said, ventilation is a good way to reduce the classified area. If you don't ventilate, any floor area up to 18" above the floor is Class I Div 2. So have a couple steps up to the office or put in a 18"tall barrier that you have to step over. Exhibit 511.1 shows this in a nice diagram.

511.3(C)(2) deals with the ceiling and is similar. You can provide ventilation, or a barrier over 18" tall to separate the classified from non-classified areas.

 

[GoldDigger]

511.3(C)(1) contains good guidance for major repair garages. Like rbalex said, ventilation is a good way to reduce the classified area. If you don't ventilate, any floor area up to 18" above the floor is Class I Div 2. So have a couple steps up to the office or put in a 18"tall barrier that you have to step over. Exhibit 511.1 shows this in a nice diagram.

511.3(C)(2) deals with the ceiling and is similar. You can provide ventilation, or a barrier over 18" tall to separate the classified from non-classified areas.

Or a "stile" with steps up to a raised door jamb and down the far side?

 

[kwired]

Check with AHJ, they may have established some standard of their own for such instances. One example that may be fairly common is they may want a 1 hour finish between the shop and other non classified areas. Other building codes may require this anyway.