[3dem] cryo-TEM rooms - air changes per hour?

[Bill & Sue Tivol]

> On Aug 28, 2017, at 12:27 PM, Stanislav Vitha <stanvitha at tamu.edu> wrote:
> 
> Hallo, 
> We are going to be remodeling our cryo-TEM room to get the humidity under control. Temperature will be maintained mostly by radiant cooling panels and humidity reduced by a dessicant air dryer unit.
> We would like to recycle at least some of the dry air.  However, since the microscope room is considered a lab, we are facing the requirement for 6 TO 8 Air Changes per Hour (ACH).
> I am concerned that maintaining low humidity (under 30%) will be quite difficult or require a big dryer unit.
> 
> All of the cryo-TEM lab design articles mention dry air requirements, some mention dry air recycling but  none of them go into specifics regarding  Air Changes per Hour.
> If you know how this is handled in your imaging facility/cryo-TEM room, I would love to hear from you.
> 
> 
> Thanks for your input.
> 
> Stan Vitha  
> 
> Dr. Stanislav Vitha      
> Research Scientist, Interim Director
> Microscopy and Imaging Center  
> Texas A&M University 
> College Station, TX 77843-2257
> http://microscopy.tamu.edu
> 
Dear Stan,
	Both the facilities I’ve managed have had about 3 air changes per hour, and requiring 6 to 8 seems excessive, but sometimes legal requirements are not too well thought out.  Recycling dry air sounds OK and should be OK for a cryoEM lab, but the law may have something to say about that, since it was probably designed to cover labs having airborne hazards, where recycling air could be harmful.  If recycling is allowed, I’m sure it could be incorporated in the design of the air handling system pretty easily.  Depending on the air volume in the lab, you might, indeed, need a large dryer.  It could be possible to dry the air only in the smaller volume of the scope room(s), while relaxing humidity requirements for prep areas, etc.
						Yours,
						Bill



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