Hepa filter vacuum systems/cryostats debate

From:Gayle Callis <uvsgc@msu.oscs.montana.edu>

This was discussed at great length a few weeks ago, and with doubts about
using a vacuum, preference was to clean (with extreme care) after daily
use, with major cleaning/decontamination at specified times. The use of
formalin fumes, heated or whatever in a cryostat chamber really is a turn
off and a total bust with PRION diseases.    

Three companies in the US supplied these with HEPA filters.   I presume
removal of used contaminated filters could be done with safety (biohazard
hoods?) but I would like to see how this is done. Is the HEPA filter inside
a sealed unit so that when removed, it doesn't recontaminate surroundings
without the need of a biohazard hood?? I would resent a false sense of

How do people who have these vacuums remove used filters? Describe this to
us please. If you don't want to rehash this subject, a private commentary
is welcome.  

In all due respect, the vacuum may be useful for cleaning up cryostat
debris, but user risk is still there no matter if cryostat is clean or not,
proximity to an open cryostat when cutting biohazardous tissue is totally
unavoidable although can be minimized with user precautions, no matter the
cleaning method. 

I would not hesitate to try vacuums IF they show safety in contaminated
filter removal, since containment is probably adequate with HEPA filter.
What kind of testing of these devices has been done to prove they are tried
and true 100% barrier during use and removal??   

I remain openminded about these systems (although I was a doubter a few
weeks ago!) and definitely see their usefulness. 


Gayle Callis
Veterinary Molecular Biology
Montana State University
Bozeman MT 59717-3610
406 994-4705
406 994-4303

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