Installing Fumehoods In a Lab

[KC79]

Hi,

I need to install 2 new fumehoods in a Lab that already contains 20 Fumehoods.
I've been told the AHU is maxed out & can't support any more fumehoods.

I have scope to replace some of the larger old fumehoods with smaller Fumehoods.

I want to know if the maximum amount of fumehoods is a function of the Design Volume of each fumehood or the amount of space open to the Lab at each fumehood sash.

Basically, can i replace a large fumehood of volume X with 2 smaller fumehoods of Volume X/2.

Thanks
KC

 

[bimr]

You have to approximately the same air volume entering the building as exiting the building.

If you do not enough makeup air, it will hard to exhaust. You also will a have time opening doors to the building.

Replacing a large fumehood of volume X with 2 smaller fumehoods of Volume X/2 is acceptable.

 

[77JQX]

When I've done fume hoods, the face velocity of air across the sash was the critical value for air handling, not the contained volume of the hoods.

 

[bimr]

What I meant to say above is that the exhaust flow in CFM is the important parameter if you want to change the size of the hoods. The building HVAC system has to allow enough air into the building when the fume is operating. The building should be slightly pressurized. If the building had negative pressure from too much exhaust flow, the exterior doors would be hard to open and the fan would have a hard time pushing out the exhaust.

77JQX is correct in stating that the face velocity is important, but that issue has to do with the capture of the fumes.

 

[KC79]

Thanks for the replies above

KC79