Is it allowable to decrease the level of a hazardous area classification, of a trench (below grade) from a Class 1, Div. 1 to Class 1, Div. 2 by using a gas detection or any other means? Note, that the trench is located in an analyzer room inside of a laboratory building.
Area Classification of a Trench (below grade) Inside of an Analyzer Room within a Laboratory Building
- Thread starter soriajxs
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petersonra
Senior Member
- Location
- Northern illinois
- Occupation
- engineer
It might be possible depending on what chemicals you are worried about. I would not bet on it though.
I guess the important question is why do you think you want to do this.
Thanks for your reply, Bob. There are flammables being sampled inside of various analyzers located directly (2-3') above the trench. If the HAC of the trench can be reduced from on C1,D1 to a C1,D2 within the trench, then the area above the trench can be considered non-classified and non-classified analyzers can be used instead of using classified analyzers. If HAC can be reduced to a C1D2 inside of the trench, what mitigation and/or requirements must be in place?
petersonra
Senior Member
- Location
- Northern illinois
- Occupation
- engineer
I think I would start by trying to determine why the inside of the trench was classified as c1d1. It is possible it was over classified to begin with.
You might be able to claim credit for better ventilation but if it is inside that probably is an issue.
Is there some reason you cannot put a solid cover over the trench where these analyzers are located. A hard break like that gives you good cause to say the classified area of the trench regardless of what that classification is ends at the hard surface.
You might be able to claim credit for better ventilation but if it is inside that probably is an issue.
Is there some reason you cannot put a solid cover over the trench where these analyzers are located. A hard break like that gives you good cause to say the classified area of the trench regardless of what that classification is ends at the hard surface.
Good recommendations, I appreciate you. I do not know the exact reason for why the trench is considered a C1D1 other than this may have been a conservative judgement call based on the fact that there are hydrocarbons within the tubing that run through the trench. I am pretty comfortable saying that the tubing in the trench do not normally leak. But can one claim anything less than a C1,D1 for this type of installation? Again the trench is inside of an analyzer room within a laboratory building.
As for a hard break like a cover over the trench, I will have to ask if this is possible. If it is, can the HAC level be reduced? If so, under what code basis?
Again, thank you very much for your follow-up and I look forward to hearing what you think about the above.
As for a hard break like a cover over the trench, I will have to ask if this is possible. If it is, can the HAC level be reduced? If so, under what code basis?
Again, thank you very much for your follow-up and I look forward to hearing what you think about the above.
petersonra
Senior Member
- Location
- Northern illinois
- Occupation
- engineer
If the trench is covered, how would any hazardous gas that might be in the trench migrate past the cover?
- Location
- Mission Viejo, CA
- Occupation
- Professional Electrical Engineer
To answer the original question, gas detection as a protective technique is limited to only three applications. [See NEC Section 500.7(K)(e)]
Applying other techniques depends on several factors; mainly, why is the trench classified in the first place? I.e., what is the source? A "cover" won't do the job to lower Division 1. Common raceways like RMC or explosion-proof enclosures can't keep flammables either in or out. They will "leak".
That said, study NFPA 45, Standard on Fire Protection for Laboratories Using Chemicals. It has been ANSI recognized since 2023, making it OSHA enforceable under the General Duty Clause.
Applying other techniques depends on several factors; mainly, why is the trench classified in the first place? I.e., what is the source? A "cover" won't do the job to lower Division 1. Common raceways like RMC or explosion-proof enclosures can't keep flammables either in or out. They will "leak".
That said, study NFPA 45, Standard on Fire Protection for Laboratories Using Chemicals. It has been ANSI recognized since 2023, making it OSHA enforceable under the General Duty Clause.