non-hazardous locations adjacent to Div 2

[lile001]

We are working on a repair garage, where they service small gas engines. There is a large warehouse adjacent to the repair garage, separated by a 2 HR rated wall with a door in it. I'm classifying the repair garage as Div 2 to 18" AFF.

The problem comes with that door. Does the fact that the door could be open mean that the div 2 area could extend into the warehouse? How far? NFPA 30A says that if we ventilate adjacent areas to 4 AC/HR, then they are unclassified. This is a 10,000 sft. warehouse with 20 ft ceilings. That could be a LOT of ventilation. If we don't ventilate the adjacent warehouse, is the whole thing classified because there is a 400 sft. lawnmower shop in one corner of it?

Also, if the ventilation fan can be turned off, or is on a thermostat, does it count toward the NFPA 30A required ventilation? I've been arguing it does not.

 

[rbalex]

The first option is to ventilate the repair room instead. If that isn't possible then the Div 2, would extend 3' into the unventilated warehouse at the door.

"Ventilation" is based on continuous air-flow.

 

[weressl]

The first option is to ventilate the repair room instead. If that isn't possible then the Div 2, would extend 3' into the unventilated warehouse at the door.

"Ventilation" is based on continuous air-flow.

Only 3'? Which diagram would you reference here Robert?

I think that negative pressure on the hazardous side would be a good option also. I would put spring closers on the doors and a warning not block them open.

 

[hazloc2002]

I think that the main concerns here are:
1- How much gas can be released in the repair garage?
2- Which gas is it? Is it lighter or heavier than air?
3- What is its LEL?
4- Comparing with the volume of the repair garage, could it produce a considerable amount of explosive atmosphere (is to say, above its LEL)?
5- Imagine that the door were opened. Could such explosive atmosphere, originated at the repair garage, go through it and keep itself concentrated enough to develop an explosive atmosphere beyond the door? (Consider the distance from the source of release until the door and ventilation at repair garage).
If your answer is yes, we can say that a Div 2 is expected in the warehouse, but not so far away from the door.