Adjacent Spaces to Class 1 Div 1 Location

faresos

Senior Member
I'm reading through section 500.5 (B) (2) (3): Class I, Division 2. A Class I, Division 2 location is a location:
"That is adjacent to a Class I, Division 1 location, and to which ignitable concentrations of flammable gases, flammable liquid–produced vapors, or combustible liquid– produced vapors above their flash points might occasionally be communicated unless such communication is prevented by adequate positive-pressure ventilation from a source of clean air and effective safeguards against ventilation failure are provided."

My questions are:
1. Does any unclassified space adjacent with door opening to Class 1 Div 1 makes it Class 1 Div 2?
2. If the classified spaces has an adequate positive pressure that will not classify the adjacent space, correct?
3. Not sure I understand "....effective safeguards against ventilation failure are provided", can you please explain how this could be accomplished?
4. Does conduit penetration between C1D1 and unclassified spaces makes the unclassified space C1D2? My thinking if we provided a seal around the conduit in the wall and conduit seals as required that should not classified the space, correct?

Thanks,
 

rbalex

Moderator
Staff member
Location
Mission Viejo, CA
Occupation
Professional Electrical Engineer
  1. Yes. See Figures 516,5(D)(4)&(5) as typical examples.
  2. Only where the unclassified or Division 2 location has a positive pressure with respect to the Division 1 location,
  3. See NFPA 496, Chapter 4 for requirements.
  4. If the penetration is effectively sealed around the conduit in an otherwise non-porous barrier that creates a "boundary", a seal consistent with Section 501.15(A)(4) is required. A "leak" around the penetration could create a Division 2 envelope around it.
 

faresos

Senior Member
Couple more questions,

1. Does Solvent Storage Room considered to be Class 1 Div. 1?
2. Do adjacent spaces to class 1 div 2 locations become classified or some special ventilation requirement is needed so adjacent spaces will not become classified?
 

rbalex

Moderator
Staff member
Location
Mission Viejo, CA
Occupation
Professional Electrical Engineer
  1. See Section 500.5(B)(2) IN No, 2 and its crossreferences. It depends on several factors but is unlikely to be Division 1. It could be Division 2 or unclassified.
  2. Again, there are multiple factors to consider to determine the extent of the Division 2 envelope. Basically, you have to draw the line somewhere,
 
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