Laboratory bench local extract arm

[remp]

Hi, I am trying to design the local extract ventilation system in a lab. Over the lab benches the user want ventilaiton arms with a hood to stretch down over the bench to where chemical etc are been mixed & tested.
What velociaty should I be looking for at the extract point? is there any code or standard out there to guide me on this? Also if I get a reccomended velocity, is this the face velocity at the widest point of the hood (200mm dia) or at the arm (100mmdia)?

 

[urgross]

The ACGIH would be a good start, chapter 10. Also, ANSI Z9.5 and probably NFPA 45.

One recommendation from experience is that you need to have either face velocity, or capture velocity and capture distance, spelled out explicitly. Face velocity would be the average velocity as described by the ACGIH, at the face of the containment device.