Ventilation and classification of area

[Britton]

Can I use ventilation alone (negative or positive forced or induced draft) to take a Class I Div 1 area and make it Div 2 or less hazardous? This is in regards to the area itself, not the inside of an enclosure.
Thanks.

 

[petersonra]

Re: Ventilation and classification of area

Can I use ventilation alone (negative or positive forced or induced draft) to take a Class I Div 1 area and make it Div 2 or less hazardous? This is in regards to the area itself, not the inside of an enclosure.
Thanks.

yes and no.

it is generally possible to create an enclosed area that is not classified or with reduced classification within an otherwise classified area. Control rooms are commonly done this way.

think about an area outside that is classified. how would any amount of ventilation change that?

 

[Britton]

Thanks

If the enclosed area has an open source of flammable vapor, can any design of ventilation change the classification from Class I Div 1 for a Class IB flammable liquid?

 

[steve66]

I think the answer can be yes based on the definitions in article 500. (Of course, the answer may sometimes be no, based on the exact conditions of a particular case.)

See the definitions of Class I Div 1 and Class 1 Div2. (NEC 500.5 (B)(1) and (B)(2).)

Steve

 

[rbalex]

Thanks

If the enclosed area has an open source of flammable vapor, can any design of ventilation change the classification from Class I Div 1 for a Class IB flammable liquid?

[rbalex bold added]

As you have described it so far, with "Adequate Ventilation" you can probably reduce the volume of the Division I location, but you will not be able to eliminate it entirely.

NFPA 497
Adequate Ventilation. A ventilation rate that affords either 6 air changes per hour, or 1 cfm per square foot of floor area, or other similar criteria that prevent the accumulation of significant quantities of vapor-air concentrations from exceeding 25 percent of the lower flammable limit.

I recommend a thorough review of both NFPA 496 and 497.