FAQs on Anoxic Disinfestation

What is Anoxic Disinfestation?

Anoxic disinfestation is a process whereby the combat against infestation by insects (one of the main causes of destruction of documents and works of art) is undertaken by asphyxia, through the use of completely innocuous gases such as nitrogen, argon or carbon dioxide.

The process is simple and is not toxic. It is based on the removal of atmospheric air and its replacement with nitrogen, argon or carbon dioxide. This method can be employed in a disinfestation chamber (an air-tight steel chamber in which the objects are placed) or in a bubble of plastic film wrapping the object (the process is extremely flexible and can be used with every kind of object, big or small).

This technique requires isolation of the documents and objects to be treated: the atmosphere inside is modified and several parameters are controlled, such as: oxygen/ carbon dioxide content, temperature, gas pressure and moisture).

Anoxic disinfestation chamber and anoxic bubble: owing to the nature of the biological cycles of the insects that attack the material of books and other substances found in the collections of libraries and in archives, the disinfestation operations have to be co-ordinated with the customer to determine the type of infestation of the documents.

Safety: the collections of museums, libraries and archives may be threatened by several pests, constituting a serious threat to their preservation. The method of pest control least prejudicial to the collections and to the personnel is carried out by means of modifying the atmosphere, an alternative to chemical control.

Anoxic disinfestation is a method that has no noxious effect on the items that are treated or on the operator. It is safe, ecological, non-toxic, non-flammable and non-chemical. It consists of wrapping the item to be treated in a special film and removing the oxygen inside. The oxygen is replaced by an inert gas, thus eradicating all insects no matter what their stage of development (egg, lava, pupa, adult, etc.).

This process is monitored by state-of-the-art equipment of extreme sensitivity and precision.

It does not modify the physical or chemical properties of the item treated, and its original form is retained, though freeing it from the action of the pests.

What is meant by preservation?

definition adapted from 'A Preventive Conservation Programme'; a paper by Dr Luisa Cabral, National Library, presented in Lagoa, Algarve on 3/10/2003

Preservation comprises a number of management measures designed to neutralise potential deterioration of documents” (IFLA).

It consists of a policy and strategic measures employed in the management of archives and libraries, the principal aim of which is to avoid the deterioration of the collection as a whole.
This field complements the general maintenance of the buildings, involving co-ordination with other departments.

In conservation strategy control of the environmental conditions is of particular importance. The main factors to consider are: Temperature and Relative Humidity, Lighting and Air.

Temperature and Relative Humidity

a) Effects: heat accelerates the deterioration of documents, high relative humidity causes oxidation and, when combined with high temperature, leads to the appearance of mould and insects. Low relative humidity makes paper fragile;

b) Ideal values: temperature should lie between 18 and 20º C and relative humidity between 45% and 55%;

c) Control Mechanisms: adequate control equipment: air-conditioning, humidifiers, dehumidifiers, air purifiers; constant monitoring: thermographs and computerised system; building maintenance.


a) Effects: light accelerates the deterioration of paper, and weakens and yellows or darkens paper. UV rays are particularly harmful owing to photochemical deterioration (high level of energy absorbed by the molecules of the object). Damage is cumulative and irreversible;

b) Ideal values: the maximum light level should not exceed 50 lux/hour;

c) Control Mechanisms: use of UV filters or optic fibre and of low UV ray emission tungsten lamps is recommended.

Air quality

Effects: acidification and discolouration of paper and leather by action of gases and particles such as nitrogen dioxide, sulphuric anhydride, peroxides and ozone. Particles, of silica in particular, are abrasive.

What is understood by conservation?

definition adapted from "Pest Control and Collection Hygiene"; a paper by Dr Katia Bettencourt, National Library, presented in Lagoa, Algarve on 3/10/2003

“Conservation is the set of measures directed at systematic, direct intervention in respect of the documents to prevent their deterioration, without altering the physical characteristics of the support ” (in IFLA).

It consists of specialised technical measures designed to correct the physical deterioration of the materials, involving no internal intervention in the work. It includes tasks and procedures that include environmental control, pest control and collection hygiene, cleaning, storage, packing, maintenance, measures to prevent, monitor and identify pests and their activity, how to act in the event of infestation, book binding and support transfer, among others. It requires assignment of specialised human resources, specialised outsourcing, basic equipment and adequate raw materials.


Cleaning is an elementary, priority and time-consuming task since, to be effective, it has to be systematic and permanent.


Proper cleaning prolongs the life of a document, avoiding contact with dust, which, in addition to being abrasive, causes the appearance of mold and attracts insects.


Observance of cleaning rules is intended to safeguard the integrity of fragile paper or bindings. In cleaning, the following should be taken into account:
– the physical condition of the documents;
– the type of dirt; the extent of the job;
– and the value of the works.

The area of the archives should be vacuumed regularly and water should not be used. When being cleaned the documents should be closed and cleaning should begin with the dirtiest part, removing items such as clips, elastic bands, bookmarks, photos, pieces of paper, etc.

Necessary equipment: cleaning must be carried out using dusters, soft brushes, bio-alcohol based detergents (with no ammonia or chlorine); the use of gloves and masks, regulated-suction vacuum cleaners and cleaning tables with suction is recommended.