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Subject: Anoxia


From: Stephan Schaefer <schae<-a>
Date: Sunday, October 12, 2008
Tamara Jaeger <tamarajaeger [at] hotmail__com> writes

>We are considering purchasing a large enclosure similar to the
>Rentokil "Bubble" for anoxic pest eradication treatments of objects
>and archival materials that cannot be frozen. I am interested in
>hearing what systems other institutions are using as well as their
>associated benefits and drawbacks.

I think there are several considerations that may be decisive for
the choice of an anoxia system. First of all, the desired maximum
volume of the chamber or bubble is probably what matters the most
and next the question of mobility and certainly whether the
institution is willing to work with gas cylinders or tanks that need
to be purchased and exchanged for every treatment or whether to
consider the acquisition of a nitrogen generator. There are
certainly several interesting options of mobile and permanently
installed chambers that have their advantages and disadvantages.
Mobile bubbles can be as big as 20-30 m3 and fixed chambers have
almost no limit to the size and come with gas tight doors. Both
types can be walk-in and are commercially available.

The next question is whether the nitrogen supply is purchased for
each treatment or if the use is considered frequent, so that a
nitrogen generator could be employed. Nitrogen generators have the
great advantage of the institution being independent of an external
supplier and there is no more need to exchange of tanks. The bigger
the chamber and the more frequent the use, the faster a generator
will pay off. Also, an institution with a rather large chamber
attached to a nitrogen generator, can profitably offer its services
to the public or other institutions. Again, there are various
technologies and N2 generators are rated by their nitrogen output
(volume: m3/hour or l/minute) at a given purity level. Nitrogen
generators for anoxia treatments should of course supply nitrogen as
pure as 99.9% which means at the most 0,1% of residual oxygen or

The new central library of the New University of Lisbon's campus of
Sciences and Technology has recently acquired a mobile anoxia
chamber of 12m3 and a nitrogen generator as part of their preventive
conservation and integrated pest management strategy. After going
through the main advantages and disadvantages of several different
systems, a decision was made to purchase a mid size mobile chamber
and a nitrogen generator and the library is already offering anoxia
desinfestation as a service to the public and other institutions.
This on the other hand can soon turn the acquisition into a cost
covering or even profitable activity while being able to cope with
any possible infestation of the library's own material and incoming
donations which are treated independently of any sign of
infestation. For further information, you can also contact me

Stephan Schafer
Prof. Dipl. Rest. Stephan Schafer
Universidade Nova de Lisboa (UNL)
Faculdade de Ciencias e Tecnologia (FCT)
Departamento de Conservacao and Restauro
2829-516 Caparica

                  Conservation DistList Instance 22:22
                 Distributed: Monday, October 13, 2008
                       Message Id: cdl-22-22-006
Received on Sunday, 12 October, 2008

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