Combining Lab Extract or General Ventilation Duct with Local Exhaust Ventilation Duct

[SiteJanny]

Can anyone advise me if it is acceptable practice to combine Lab Extract or General Ventilation duct, with an LEV exhaust duct?

I'm conducting a review of proposed LEV installations in a new Hospital under construction, and most of the exhaust ducts for the various LEV's appear to take additional connections from lab extract ducts and in some cases from general ventilation extract.

I've checked all the regs I can find including information in HTM 03-01, HSG 258, NFPA 45 & 91, SMACNA, ANSI/AIHA Z9.5, OSHA and ASHRAE and as detailed as these regs all appear to be, none of them addresses this question.

LEV's I've dealt with in the past had dedicated exhaust ductwork and fan installations with no additional connections to either lab extract or general ventilation. Common sense tells me this is wrong because of the potential for cross contamination, but as the old adage goes - 'never assume, check!'

In the absence of hard evidence that the installations are non compliant, I'll be unable to flag the concern.

 

[urgross]

I think this is answered at NFPA 45, 7.5.10.3. If all exhausts are from the same laboratory unit, they can be manifolded. Of course, usage compatibility, such as general hoods vs. perchlorate or isotope, would have to be considered. The routing of the laboratory exhaust might be an additional issue, based on the IMC field interpretation of subducting requirements.

 

[trashcanman]

Regardless of what any codes say, I would NOT sign off on it. You don't know what may be in the lab exhaust. Corrosive fumes, explosive, ebola....? Better safe than sorry.

 

[urgross]

Just like deaaling with NFPA 30, it's the Laboratory Director that is responsible for providing the MSDS and storage quantity to be used with LEV, hoods and dilution ventilation. My experience is that it is typcially the CIH that determines compatibility and the ME that determines that the system will perform. If the Laboratory Director changes usage afterwards, it is on their dime to consult with the CIH.

 

[SiteJanny]

Thanks for your input guys

@urgross - I'd noted the NFPA 45 comment about manifolding from the same Lab. But my concern lingers largely because of the difference between the term 'exhaust' and the term 'extract'. Further, I also have a mental block over the term 'Laboratory Unit'. I may be looking way too deep at the question but in essence, I can't get past the idea that this should really mean manifolding the extracts from one space.

To clarify my concern a little - one example here, I'm looking an LEV duct that combines three fume cabinet exhausts. All perfectly good to me. But then downstream, that duct accepts connections from a variety extract ducts from the likes of a Waste Room, a Cold Storage Room and a Growth Production Room. Now to my mind they simply cannot be considered as being the same Lab Unit. Or am I overdoing things here?

 

[Drazen]

lab extract demands are completely dependent on type/composition of exhaust fumes, which imposes requirement for duct materials and leakage control.

other than that, cross-contamination exists if it can be proven, which is likely not the case with local exhaust.

 

[urgross]

Definitely not overlooking it. From my experience, a Laboratory Director must be appointed in writing and have absolute control of a laboratory unit. Each laboratory unit may consist of multiple laboratories. The NFPA 45 definition is very loose. If more than one Laboratory Director is appointed, more than one isolated exhaust system is needed.