RE: [ccp4bb] harvesting in cold roomDensity of LN2=807g/L, that's roughly 807/28*22.4=645.6L gas at RT, 1 atm. At 4C the volume will be less: 645.6/298*277=600L. An empty 2x2x2m cold room=8000L, containing 8000x21%=1680L oxygen. We normally won't let the whole liter of LN2 to evaporate when freezing crystals. But if someone leaves a liter of LN2 in a small cold room and forgets to take it out before it all evaporates, then it can become a potential hazard to next user. We have to consider that some labs also use cold room as storage place, that might also greatly reduce the volume of air inside. I guess the case could be even worth with CO2, as CO2 gas is denser. If someone has a large bag of dry ice subliming in a closed space, then it can fill the space from bottom. So, lighting a candle when work in cold room? I am not sure if the fire department will like it.
From: Green, Todd Sent: Friday, July 13, 2012 5:51 PM To: CCP4BB@JISCMAIL.AC.UK Subject: Re: [ccp4bb] harvesting in cold room I've noticed that pretty much every time there is an autofill of the dewars in the hutches of SSRL or APS, the oxygen sensors go off. but that is a small space and many liters of liquid nitrogen. I've frozen routinely in a small cold room with a liter or 2 of liquid nitrogen with no issue. -----Original Message----- From: CCP4 bulletin board on behalf of Jacob Keller Sent: Fri 7/13/2012 4:42 PM To: CCP4BB@JISCMAIL.AC.UK Subject: Re: [ccp4bb] harvesting in cold room How frequently do the sensors go off? JPK On Fri, Jul 13, 2012 at 4:37 PM, David Schuller <dj...@cornell.edu> wrote: > On 07/13/12 17:29, Jacob Keller wrote: > > You probably already know this, but nitrogen is not at all > poisonous--about 78% of the air is nitrogen. I guess you were probably > worried about asphyxiation....? > > > We have oxygen sensors in our X-ray hutches for precisely that reason. > > -- > ======================================================================= > All Things Serve the Beam > ======================================================================= > David J. Schuller > modern man in a post-modern world > MacCHESS, Cornell University > schul...@cornell.edu > > -- ******************************************* Jacob Pearson Keller Northwestern University Medical Scientist Training Program email: j-kell...@northwestern.edu ******************************************* This email was scanned with Mcafee's Anti-Virus appliance, but this is no guarantee that no virus exists. You are asked to make sure you have virus protection and that it is up to date.
