ANOXIA - TREATMENT BY OXYGEN DEPRIVATION :
OPTIMIZING TREATMENT TIME OF MUSEUM OBJECTS
Michèle Gunn1*, Houri Ziaeepour2, Fabrice Merizzi3, Christiane Naffah4
1 Musee Quai Branly, 55 quai Branly, 75007 Paris, France.
2 Mullard Space Science Laboratory, University College London, Holmbury, St.
Mary, Dorking, RH5 6NT, Surrey, UK.
3Department of Islamic art, Louvre Museum, 34 quai Louvre 75001 Paris,
4 Centre de Recherche et de Restauration des Musées de France
14 Quai François Mitterrand 75001 Paris, France.
ANOXIA, treatment by oxygen deprivation is largely used for decontamination and
disinfestation of cellulose and protein-based organic materials. More specifically this method
is applied to more than one hundred thousand of objects destinated for a new museum in
Paris, "Musee du Quai Branly". We describe the anoxia installation in this museum and
report the result of a study regarding the efficiency of this method and the optimum treatment
time, crucial for treating a large collection. We show that the standard 21 days of exposure is
not always the optimal choice. Temperature plays a crucial role for hastening the death of
insects found within objects. At a temperature of 25°C, it is entirely possible to reduce
exposure times to 10 or 15 days for the insect species commonly found in museums. The
oxygen drop times is between 1 and 2 days for most objects, depending on type and porosity
of materials. This corresponds to a treatment time between 15 and 16 days. The effect of
humidity is less clear. It can increase the necessary treatment time both for larvae and for
Correspondence should be addressed to M.G. (email@example.com)
A large part of the collection of the future Musée du quai Branly - currently under
construction near the Eiffel Tower in Paris - is composed of cellulose and protein-based
organic materials. Such materials are favourable media for the development of micro-
organisms and insects, leading to their degradation.
This collection is presently being treated in a series of steps which include cleaning,
the taking of photographs, packaging and biological decontamination in the Le Berlier
building which has been especially equipped for this purpose.
The collection of the Musée du quai Branly, numbering about 275000 objects1,
comprises on the one hand collections from the Musée National des Arts d’Afrique et
d’Océanie (MNAAO) and the Musée de l’Homme (MH), and on the other hand has been
enriched by new acquisitions.
Studies of the general state of conservation of these collections in their original
institutions by experts, demonstrated the existence of infestation by Anobiidae, Dermestidae
and Tineidae, to name just a few. Infestation was found to be more or less serious depending
on the institution and departments in question. Given that it is difficult to reconstruct an
accurate case history of the infestation and the steps that have been taken to counter it, it was
decided to proceed with treatment of all objects containing organic materials, without
This prudent choice was made in view of the fact that the treated objects were not
destined to return to the site from which they came, but were going to be housed in a new
museum: a « complete overhaul » of the objets in order to reduce the level infestation to zero
is advisable under such circumstances. Furthermore, the objects are treated by oxygen
deprivation (anoxia), which minimises the risk of chemical degradation, althought some
discolorations of some pigments have been reported (TOSHICO, K., 1980); this cannot be said of
classical fumigation treatments even though the treatment times are much shorter in the latter
Heritage institutions currently employ oxygen deprivation treatment times (Tt) of 21 days.
This duration appears to have been adopted in the light of the results of experiments carried
out on a particularly resistant species, the rice weevil, an important pest in the food
industry : 500 hours (21 days) at 26°C, 12% relative humidity, in a nitrogen atmosphere
containing 1% oxygen. The exposure time is extended to 1000 hours (6 weeks) if the
temperature is lowered to 20°C (SELWITZ, C. et al, 1998).
Of more relevance in the museum field, the old house borer, Hylotrupes bajulus, is also a
species resistant to treatment by oxygen deprivation. Its favourite medium is resinous wood.
Eradication of this insect necessitated 20 days in somewhat different conditions: 20°C and
40% relative humidity. The duration can be reduced to 10 days if the temperature is raised to
30°C (VALENTIN, N., 1993).
It has gradually become standard practice to use a treatment time of 21 days. The
recommended conditions are in general as follows: less than 0.1% oxygen, a temperature
above 20°C and relative humidity of 50%.
The exact number will be established at the end of the collection treatment programme
There are a very large number of objects to be treated (more than 80% of the collection).
The deadline for completion of the collection treatment programme leads to constraints, in
view of which time is of the essence. It is therefore appropriate to analyse the time given to
each stage of the object treatment process in order that none be wasted.
If a reduction in the duration of oxygen deprivation treatment turns out to be possible, this
would enable a good speed to be maintained during the progress of the collection treatment
Consequently the key conclusion awaited from this study is the answer to the following
question: is the anoxia treatment efficient for an exposure time less than 21 days ?
Each anoxic treatment installation has its own characteristics. Thus, since the installation
we have used, named EPMQB (named according the name of the musée, Etablissement
Public Musée du quai Branly2), was specially designed for the Musée du quai Branly
treatment site, and was of a new and as yet untried form in the field of heritage and
conservation, it was necessary to carry out a study in order to optimize the conditions of
treatment for objects, in particular as regards oxygen drop times and exposure times.
The feasibility of treating infested museum objects by oxygen deprivation, either through
the use of oxygen scavengers, or in a controlled atmosphere of an inert gas such as nitrogen
(N2) or argon (Ar)) or carbon dioxide (CO2) is now well established. Resistant species such as
H. bajulus or A. punctatum (cellulose) can be totally eradicated, and this is also possible in
the case where insects are at the egg or larval stage which renders them more resistant to
treatment (Rust, M. et al, 1996 ; Selwitz, C. ; Maekawa, S., 1998). Many studies have already
been carried out by teams in the USA (Getty Conservation Institute) and Australia
(Australian Museum) for exemple. These studies have enabled the evaluation of influence of
different parameters, such as the level of oxygen (O2), temperature and relative humidity, on
the exposure times needed to achieve 100% mortality whatever the life cycle stage of the
Therefore, the goal of the study is to determine the efficiency of the EPMQB equipment
and the effectiveness of the traitement in the case of insects buried deep within an object.
This phase of the study should enable the degree to which oxygen is removed from the inside
of treated objects to be evaluated.
We report and discuss results obtained in the following areas :
1) the exposure time, Te, in the new EPMQB installation, leading to 100% mortality
irrespective of life cycle stage of the insects present in infested objects. The treatment
conditions are based on previous literature reports. They must be optimized from a mortality
viewpoint whilst avoiding endangering at the same time the physical structure of the treated
objects: an atmosphere with highly reduced oxygen content is used, between 1000vpm and
30vpm, a temperature of 25°C± 1°C and hygrometry of 50%± 5%.
2) the oxygen drop time, Ti33, defined as being the time taken to lower the oxygen
content in the treatment unit to the required level (0.1 %), and to study the effect of the
degree of loading with museum objects.
3) the oxygen desorption time of the objects Td. The Td value depends intrinsically on
the nature of the materials and the volume of the objects to be treated and the volume of the
Public Institution Musée du quai Branly
Ti, i for inert
anoxia chamber. The Td varies as a function of the permeability of the materials to gases, i.e.
nitrogen and oxygen in this case.
A - PROGRESS IN OXYGEN DEPRIVATION TREATMENT: MAIN RESULTS
OBTAINED BY OTHER INSTITUTIONS
I-TESTS ON INSECTS: EXPOSURE TIMES AND CLIMATIC CONDITIONS OF
The experiments carried out cover a very wide range of insects at all life cycle stages, i.e.
eggs, larvae, nymphs and adult insects. Atmospheres were modified through the use of the
three most frequently used gases: carbon dioxide (CO2), nitrogen (N2) and argon (Ar). The
anoxia treatment was performed in bubble chambers (VALENTIN, N.,1994; RUST, K. et al., 1996).
In some cases in order to simulate their being buried, insects were prepared in glass tubes
closed by a system allowing gaseous exchange. The tubes were subsequently left fixed within
blocks of wood. Other experiments were with sections of pine wood and with books of
dimensions which were artificially infested with the insects to be studied. The main results
show that :
- the most resistant life cycle stages of insects are eggs and larvae;
- not all the insects react in the same way, the old house borer is the most resistant;
- the treatment is more effective with argon than with nitrogen;
- temperature is an important factor whatever the other conditions.
The exposure time is reduced when the temperature increases; for example in the case of
H. bajulus (old house borer), when the temperature increases from 20°C to 40°C, the
exposure time is reduced from 21 days to 2 days. The studies carried out in the museum
environment show exposure times much lower than the standard of 21 days when the
climatic conditions are chosen appropriately, including for the most resistant species; for
- for the Anobiidae
or 5 days with 50% relative humidity, 30°C et 0.03% oxygen. One exception to this
range has been reported; this is Lasioderma serricorne (cigarette beetle), which
required 8 days at 25°C with 50 % relative humidity, or 9 days at 20°C and 40 %
relative humidity. (VALENTIN, N., 1993);
(e.g. : furniture beetle), complete elimination was achieved after 3
- for Hylotrupes bajulus (old house borer) of the Cerambycidae family, which has
shown itself to be rather more resistant, the exposure time was 10 days at 30°C with
40 % relative humidity or 20 days at 20 °C. (VALENTIN, N., 1993);
-for the Tineidae (e.g. clothes moths), 4 days at 25.5°C, 55% relative humidity and an
oxygen level below 0.1 % have been reported (RUST et al, 1996).
More recently in 2000, a Japanese team proposed a practical protocol for anoxia treatment
according to the type of insect. They advise 25°C or 30°C for one to three weeks. When the
temperature is 20°C exposure time should be extended to 10 weeks with an oxygen level of
A study of the resistance of Tribolium castaneum (Red flour beetle) to a reduced oxygen
atmosphere was carried out using the following conditions: 0.5% oxygen in nitrogen, or 20%
oxygen and 15% nitrogen in carbon dioxide with 95% relative humidity, these conditions
being maintained until only 30 to 50% of the insects were still alive. The surviving insects
were bred for 40 generations in the same conditions. This study showed that these insects
were only resistant towards the specific atmosphere to which they had been subjected. Insects
returned to normal air after 13 generations displayed continuing resistance for 8 generations.
The authors of this study considered that adaptation to atmospheres modified with carbon
dioxide is more likely to occur than in the case of modification with other gases. More
recently, in 2001, HOBACK and STANLEY studied several microhabitats where insects are
under hypoxia or anoxia such as stored grain or decaying wood. In such conditions insects
reduce their respiration rates when the oxygen level reached 10 %. Certain insects as C.
vomitoria larvae can survive at 1 % only 5-6 days. However, in general, insects cannot
withstand an oxygen level of 0.5 % for a long period of time.
It would not be realistic to consider that the simple fact of subjecting aerobic insects to
an anoxic environment is sufficient to make them become anaerobic species.
The rice weevil, whose resistance seems to have given rise to the standardized
treatment time of three weeks, is an important pest in the agricultural industry. This insect is
not among those frequently encountered in museums. In museums, the insect population
is essentially composed of Anobiidae, Dermestidae, Tineidae, and other families such as the
Lyctidae and Lepismatidae (MAEKAWA, S., 1998, PINNINGER, D.). These insects are much less
resistant to oxygen deprivation treatment as is indicated by the results of studies involving
The conclusions we draw after the study carried out with the EPMQB installation are
based both on the results of teams abroad working in this field and on our observations at the
Musée du quai Branly.
Temperature plays a crucial role for hastening the death of insects found within
objects. Thus, at a temperature of 25°C, it is entirely possible to reduce exposure times to 10
or 15 days for the insect species commonly found in museums.
The role played by humidity is less clear-cut in spite of the fact that the principal
mechanism leading to insect mortality is desiccation, both for larvae and for adult insects.
In view of the results obtained with the EPMQB installation and also in view of those
recorded in the relevant literature for tests on reference samples and on real objects (such as
the results of the Getty Conservation Institute), and taking account of the experimental
conditions (temperature, relative humidity, oxygen levels) we can move as of now to an
exposure time (Te) of 14 days (2 weeks).
The oxygen drop times (Ti) being situated between 1 and 2 days for most objects, this
corresponds to a treatment time Tt between 15 and 16 days.
Tt = Ti + Te
In parallel with the treatment of objects, the rigorous hygiene monitoring programme
put in place on the collection treatment site will enable any new infestation to be detected.
For this monitoring programme, the Musée du Quai Branly has called in specialists in
tackling infestation. The hygiene monitoring programme involves the setting up of
pheromone and baited traps and these traps are renewed every three months.
A programme of harvesting and identification of insects has also been initiated. A list of all
the insects found dead or alive, in the treatment sites or on objects is kept by the
Cleaning/Dusting Department and transmitted to the Anoxia Department, who are
responsible for identification, performed in collaboration with the company Hygiène-Office
and the Laboratoire d'Entomologie du Muséum d'Histoire Naturelle6.
BANCK, H., J, ANNIS, P., C., "Suggested procedures for controlled atmosphere storage of dry
grain”. Commonwealth Scientific and industrial Research Organization ( CSIRO)
Division of Entomology Technical Paper, 13.
BEAR, J., “Hydrodynamic Dispersion”, 1963
KIGAWA, R., et al “Practical methods of low oxygen atmosphere and carbon dioxide
treatments for eradication of insect pests in Japan” in proceedings of 2001: Integrated Pest
Management for Collections . A Pest Odyssey. 1-3 October 2001, chapter thirteen.
HOBACK, W.W; STANLEY, D.W. “Insects in hypoxia”, J. of Insects Physiology, 2001, 47, 533-
PINNINGER, D., “New Pests for old : The changing status of museum insect pests in the UK” in
proceedings of 2001: Integrated Pest Management for Collections . A Pest Odyssey. 1-3
October 2001, chapter three.
RUST, M., VINOD, D., DRUZIK, J., PRESSEUR, F.,“ The feasability of using modified atmosphere to
control insect pests in museum”, Restaurator, 1996, 17, 43-60.
SELWITZ, C. , MAEKAWA, S., “Inert gases in control of museum insects pests”, Ed. The J. Paul
Getty Trust, 1998.
VALENTIN, N., 1993,“Comparative analysis of insect control by nitrogen, argon, and carbon
dioxide in museum, archive and herbarium collection”, International Biodeterioration et
Biodegradation, 1993, 32, 263-278.
VALENTIN, N., PREUSSER, F., “Insect control by inert gases in museums archives and archives”
Restaurator, 1990, 11, 22-33.
We thank Mr. Stéphane Martin, Director of the Musée du quai Branly, for entrusting us with
We also thank the company Hygiène Office for the wooden boxes used in the gas diffusion
experiments and the company Mallet for agreeing to modify the installation in line with our
needs for this research programme.
Entomology department of the Natural History Museum, Paris)
We thank Mr. David Pinninger for his assessment of this study, which enabled the Musée du
quai Branly to decide if and how it should be implemented.
We thank Mr. Jean-Pierre Mohen, Director of C2RMF7 for his advice on this project.
We also thank Mr. Jason Hart-Davis for help with the English of this report, and thanks also
go to the photographic team of the Musée du quai Branly, and in particular to Ms. Stéphanie
Centre de Recherche et de Restauration des Musées de France (French Museums Research and Restauration