Oil Storage Room (Flammable Storage, Class I, Divisioin II, Group D

[bpatt66]

I have run across a number of facilities that have a flammable storage room for storage of oil containers. The facilities that I have seen are usually constructed between 1950 and 1980, having the flammable storage use an entrance from the exterior. Most rooms are simple, having explosion proof lighting controlled from a switch on the wall outside. Sometimes I will see a pull station for the fire alarm in the storage room. Recently I have run across a facility with an explosion proof smoke detector and (4) hydrocarbon sampling devices on the walls mounted (2) at the ceiling and (2) at the floor.

I also have two new projects where I have been asked to replace or install a new fire alarm/mass notification system, one larger facility has existing hydrocarbon sampling equipment in the flammable storage room, the other has no existing fire alarm system or hydrocarbon sampling.

I have two questions:

1. It is not clear to me whether hydrocarbon sampling is required in both facilities. What code reference requires the use of hydrocarbon detectors?

2. I generally prefer to avoid installing electrical equipment in hazardous locations. Does NFPA 72 have exceptions for strobes, speakers, or devices that my gut instinct tells me I might like to avoid?

 

[rbalex]

1. See Section 500.7(L) and its Informational notes; i.e. read it all. Note that combustible gas detection is only a protection technique and is not required if other proper protection techniques are used.

2. NO. In the absence of a specific provision in the NEC itself (there isn't one), NFPA 72 cannot circumvent NEC requirements. The equipment you mentioned would generally fall under Section NEC 501.105.

NOTE: Depending on the actual activities carried out in the storage rooms and other factors of the surrounding location, classification may not be necessary in the first place. There are too many unknown factors in your post to be definitive.

 

[bpatt66]

Thanks, I should have included the following information; Both rooms discussed above are noted on drawings as Class I, Division 2, Group D. Figuring out why one room has gas detection equipment and the other does not has been challenging as this is a new subject for me.

I still have some confusion as I can't explain the differences between the room that has the gas detection system, and the room that does not have gas detection.

If I understand correctly, NFPA 70 does not seem to require "gas detection equipment" in a Class I, Division 2, Group D area. My conclusion would be based on the use of the words "shall be acceptable protection techniques" in 500.7., and 500.7(K)(1) allowing "inadequate ventilation" for a Class 1, Division 1 location (which is a more severe condition than Class 1, Division 2). I am assuming that inadequate ventilation in Class 1, Division 2 areas is already permitted to be "inadequate ventilation" as it is not specifically called out here, a leap that seems logical, but not fully substantiated by 500.7(K)(1) as it is worded.

I'm not finding conclusive information to explain why the rooms are different, but my reading of NFPA 70 would lead me to conclude that "gas detection equipment" was included in one of the rooms as either "optional" equipment for extra protection, because code has changed (unlikely, but I can't prove), or because another code that I am not familiar with requires the gas detection equipment.

Of most concern to me would be whether as a designer I am required to install the "gas detection" equipment in the room that does not already have detection when installing a new fire alarm system. I have the impression that I have grounds to say that gas detection is not required. Would there be anything that you are aware of that I may have misread/misinterpreted, other codes I should be looking at, or other conditions that I should be considering? I have no issue "recommending" equipment to be installed, but would like to be on firm footing when I say that it is "required".

 

[kwired]

500.1

Articles 500 through 504 cover the requirements for electrical and electronic equipment and wiring for all voltages in Class I, Divisions 1 and 2; Class II, Divisions 1 and 2; and Class III, Divisions 1 and 2 locations where fire or explosion hazards may exist due to flammable gases, flammable liquid–produced vapors, combustible liquid–produced vapors, combustible dusts, or ignitible fibers/flyings.

I don't see that a liquid causes a classification covered in this section(s) unless it produces combustible vapors, at least at the ambient temperatures expected. Most "oils" and even diesel and similar fuels do not easily give off combustible vapors at typical environmental temperatures and do not create a classification here.

 

[rbalex]

Thanks, I should have included the following information; Both rooms discussed above are noted on drawings as Class I, Division 2, Group D. Figuring out why one room has gas detection equipment and the other does not has been challenging as this is a new subject for me.

I still have some confusion as I can't explain the differences between the room that has the gas detection system, and the room that does not have gas detection.

If I understand correctly, NFPA 70 does not seem to require "gas detection equipment" in a Class I, Division 2, Group D area. My conclusion would be based on the use of the words "shall be acceptable protection techniques" in 500.7., and 500.7(K)(1) allowing "inadequate ventilation" for a Class 1, Division 1 location (which is a more severe condition than Class 1, Division 2). I am assuming that inadequate ventilation in Class 1, Division 2 areas is already permitted to be "inadequate ventilation" as it is not specifically called out here, a leap that seems logical, but not fully substantiated by 500.7(K)(1) as it is worded.

I'm not finding conclusive information to explain why the rooms are different, but my reading of NFPA 70 would lead me to conclude that "gas detection equipment" was included in one of the rooms as either "optional" equipment for extra protection, because code has changed (unlikely, but I can't prove), or because another code that I am not familiar with requires the gas detection equipment.

Of most concern to me would be whether as a designer I am required to install the "gas detection" equipment in the room that does not already have detection when installing a new fire alarm system. I have the impression that I have grounds to say that gas detection is not required. Would there be anything that you are aware of that I may have misread/misinterpreted, other codes I should be looking at, or other conditions that I should be considering? I have no issue "recommending" equipment to be installed, but would like to be on firm footing when I say that it is "required".

From my experience, gas detection is used by folks that want a "warm-fuzzy" feeling because they don't know what else to do. Trying to determine a significant difference between the rooms in your OP with and without such detection is likely to prove fruitless.

Gas detection has never been a requirement in any relevant ANSI standard that I am familiar with. (And I know most of them fairly well) Combustible Gas Detection was not an NEC recognized Protection Technique until 2002. In my opinion, at the time it should have been the subject of an NFPA Standard like NFPA 496 for purging/pressurizing before it was accepted or at least had a simultaneous adoption.