When do we need a Haz Classification in a Lab?

[haze10]

So NFPA says that the mere presence of a flammable does not necessitate a hazardous area classification. So no one would question the lab chemist pouring acetone from a one liter beaker into a test tube on a lab bench, insisting that necessitates a hazardous area classification. At least I wouldn't. But what if he is filling a 10 liter reactor and pouring out of a five gallon can? What if he wheels in a 50 gal drums and hand pumps out of it into the reactor?

There is a point where the quantity of the flammable is going to necessitate a hazardous area. But NFPA 497 doesn't really define that quantity. In NFPA 45 they look at fire hazards, NFPA 45’s objectives are to:

limit injury to the occupants at the point of fire origin
limit injury to emergency response personnel
limit property loss to a maximum of one laboratory unit..

This is specific to sprinkler protection for lab space and building.

I would think we could guess at some basic concepts.
The broken test tube of acetone could form and ignitable concentration, but it would be a very limit flash with relatively low pressure.
The broken liter of acetone could form a a larger deflagration, may raise loose ceiling tiles but maybe not blow out the windows.
The gallon jug of acetone makes even a bigger deflagration and possibly blows out the windoes.
At the five gallon mark a spill could form a large deflagration and possibly move stud walls.

But where are the standards to advise us. You can't just go by air exchanges cause at the time of the spill some volume in ignitable. Plus NFPA doesn't really permit dilution as a solution. Purged enclosures are different as their function is to keep the flammables OUT of the enclosure.

What are your thoughts about where you drawn the line in the sane and tell the chemist, this much, and no more.

 

[PersonalProfile]

The following historical LinkedIn discussion may be of interest as a start, despite that you may be aware etc:

https://www.linkedin.com/feed/updat...41?utm_source=share&utm_medium=member_desktop

 

[eeprom]

The presence of exposed, highly volatile flammable liquids does constitute a hazardous area, and for that area there will be boundaries, within which all electrical must be suitable for that hazard. The hazard you have is class I, which is for the most part hydrocarbons. My guess is that since you have a lab, you probably have ventilation, which will mitigate the hazardous vapors of acetone.

In any case, yes, it is definitely a hazardous location. Determining the extent of it is not simple. There is a standard NFPA 45 - Standard For Fire Protection for Laboratories Using Chemicals. I would start there.

 

[haze10]

thanks for the response, there hasn't been many.
THe NFPA states that the mere presence of a flammable does not necessitate a hazardous rating. I am well acquinted with the NFPA articles, but they don't answer my question.
As stated, 1ml of acetone in a test tube would not necessitate a haz rating, but 5 gallons probably would.
You can't use air dilution as regardless of the air transfers, you have to have an ignitable concentration somewhere off the spilled fluid.
So where do you set the quantity limit. I did come across one white paper that recommended 2.5 liters.

 

[FacEngrPE]

Consider the possible upset condition from a HAZOP perspective.
[ul]
[li]Upend largest single container of flammable liquid.[/li]
[li]Will the ignitable vapors reach a potential ignition source before an effective cleanup can be completed?[/li]
[/ul]
Now make some conservative choices regarding the hazard zone boundaries. I agree starting with NFPA 45 is a good idea. I would consider these standards
[ul]
[li]NFPA 30 Flammable and Combustible Liquids Code[/li]
[li]NFPA 329 Recommended Practice for Handling Releases of Flammable and Combustible Liquids and Gases[/li]
[li]NFPA 497 Recommended Practice for the Classification of Flammable Liquids, Gases, Vapors and of Hazardous (Classified) Locations for Electrical Installations in Chemical Process Areas[/li]
[li]FM Global Property Loss Prevention Data Sheets[/li]
[/ul]