Methyl bromide, an ozone-depleting chemical, has long been used internationally to fumigate buildings and museum artefacts.
Use of the fumigant is being phased out in many overseas countries, and the museum is trying a different technique, called anoxia, to kill any borer or other insect pests in its artefacts by depriving them of oxygen.
Museum senior conservator Francois Leurquin said about 15,000 artefacts were recently treated in this way before being transferred to the museum's new climate-controlled storage building.
The method had been used successfully in several overseas countries but this was its largest scale use in a New Zealand museum, he said.
The artefacts were treated in 15cu m lots, with double-thickness PVC sheeting used to form a tightly sealed "bubble" around artefacts and nitrogen gas released inside.
About 800 other artefacts, including larger items, had been "treated" by using an off-site freezing system, part of which involved keeping artefacts at -30degC for some time.
The anoxia technique was an effective way of killing bugs without leaving toxic residues inside the museum or otherwise damaging the environment, Mr Leurquin said.
