[NHCOLL-L:3626] RE: effects of nitrogen gas?

[Andrew Campbell]

Hi Leishawn,



   The occasional science demonstration with liquid Nitrogen poses no  
danger to the collection through the effects of Nitrogen, N2, gas.   
N2 is inert, and will not react chemically with exhibits or  
specimens.  Earth's atmosphere is 78.084% Nitrogen gas, and the  
effect of the diffusion of a small amount from a Dewar is negligible.

   The danger of liquid Nitrogen to the collection is the freezing  
and temperature shock potential, this along with the dehumidification  
of the chilled air (the fog from dry ice) and precipitation of this  
water onto surfaces.  However, if you are not conducting chemical  
demonstrations in close proximity to your specimens' microclimates,  
the liquid Nitrogen is not a problem.

   Be sure that you are using liquid Nitrogen rather than liquid  
air.  As the Nitrogen boils off from the liquid air, you are left  
with liquid Oxygen, which has a higher boiling point.  Liquid Oxygen  
is a very pretty blue color, but is highly flammable and explosive.

    N2 can be used as part of a fire suppression system by displacing  
O2 in a room and asphyxiating the fire.  The N2 fire suppression  
systems I checked on line reduce the concentration of O2 in the local  
atmosphere from 20.946% to about 12% and extinguish the fire.   
Unhappily, as an atmosphere with less than 19.5% O2 is considered  
IDLH (Immediately Dangerous to Life and Health) this system would  
also 'suppress' any curator, collection manager, volunteer, or  
visitor caught in that environment.

   Again, N2 is inert and will not react with anything in a museum  
environment.



Cheers,

Andrew Campbell

SNOMNH


On Oct 31, 2007, at 6:34 PM, Colin Macgregor wrote:

> Hi Leishawn,
>
> At the Australian Museum in Sydney we use pure nitrogen gas as a  
> method of killing insect infesting our collections. Natural Science  
> and organic cultural objects are routinely put into a chamber of  
> pure nitrogen for two weeks. We have never observed any harmful  
> effects on the objects, but it asphyxiates the bugs very  
> effectively due to the lack of oxygen.
>
>
>
> We also have a fire suppression system  in a number of our stores  
> which consists of nitrogen and carbon dioxide. There should be no  
> problem with this as the nitrogen gas is fairly unreactive. There  
> is such a large amount of nitrogen in the air around us that  
> reactions would probably have already happened if they are going to  
> happen.
>
>
>
> It’s the nitrogen dioxide and sulphur dioxide which you will find  
> in the polluted urban air outside that will attack the collection  
> under certain conditions. And then we have to look at filters on  
> the air-conditioning system etc, but that’s another story.
>
>
>
> Regards,
>
> Colin Macgregor
>
> Manager
>
> Conservation
>
> Australian Museum
>
>
>
>
>
> From: owner-nhcoll-l at lists.yale.edu [mailto:owner-nhcoll- 
> l at lists.yale.edu] On Behalf Of Leishawn Spotted Bear
> Sent: Thursday, 1 November 2007 12:32 AM
> To: NHCOLL-L at LISTS.YALE.EDU
> Subject: [NHCOLL-L:3621] effects of nitrogen gas?
>
>
>
> Howdy,
>
>
>
> A fellow colleague has been approached of having the occasional  
> chemical demonstration of liquid nitrogen to be held in their  
> museum.  She is curious to know of any effects that the nitrogen  
> gas may have upon artifacts and specimens.  Has anyone had a  
> similar situation?
>
>
>
> Thanks,
>
> ~ Leishawn
>
>
>
>
>
> Leishawn Spotted Bear
>
> Assistant Curator of Science
>
> Fort Worth Museum of Science and History
>
> 1501 Montgomery Street
>
> Fort Worth, Texas 76107
>
> 817-255-9323
>
> The Australian Museum.
>
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