Spacing between C1D1/C1D2 areas and non-classified electrical fixtures.

[Schoon]

Hey all,

I work in a medical cannabis extraction facility, and we have run into a debate as to what the spacing needs to be from the doors to our C1D1 extraction booth and electrical/data outlets on the wall directly across. We have seen 3ft thrown out in a few places, 5ft in others. Can anyone point me towards regulations that will give us a hard distance to work off of.

Thanks,
JS

 

[rbalex]

Since I have no experience with your type of facility, I can only hazard a guess. It would appear someone may have decided to apply their understanding of Article 516 or a similar concept. I would note that the "spacing" outside the doors would still be Division 2 locations.

 

[Schoon]

Thanks for the response! Would the entirety of the room outside of the booth be zoned C1D2 then? The designer stated that the area 3ft around the booth would be C1D2 so long as we kept electrical outlets out of the picture. I can add that the booth is well ventilated, drawing air from the room through the booth and out through a roof stack. We use hydrocarbons for extraction in a closed loop system. These hydrocarbons are seldom vented from the system.

 

[rbalex]

As I mentioned, I have no experience; however, there are a few things I would consider if I were to take on such a project.

• If I were to use Article 516 initially as my basis, ventilation would not generally enter into my evaluation unless I also intended it to reduce the area classification inside the enclosure to Division 2. If I did use ventilation I might also consider a combustible gas detection system under Section 500.8(K)(1). To be honest, I probably wouldn't use ventilation to reduce the classification.
• The 3' hazard radius envelope(s) would be typically be limited to openings in the enclosure. It may be increased a bit by considering the distance of the actual source of the ignitable gases/vapors to the openings. "Openings" could be permanent or include what may normally be closed during operation but could also be opened, such as access doors or louvered vents. See Figure 516.5(D)(4) sort of as an example.

 

[Schoon]

Thanks for the pointers towards NFPA 70 516. We are using the ventilation simply to prevent buildup of the gasses, but intend for the space to remain C1D1. We also have a gas detection system in place. The booth is enclosed, with one open face with sliding glass doors. That 3' hazard radius fits into what we have previously seen in other regulations. The booth is 8'x16' with the extractor situated towards the wall furthest from the sliding doors. I believe that gives us about a 12'-14' span from the extractor to the nearest non-classified electrical outlet.

 

[rbalex]

Just curious; why have a gas detection system? Not that you can't of course, but it isn't any of the recognized protection technique applications listed in Section 500.8(K). It would seem to me that a genuine Division 1 location would be alarming often, if not constantly.