Presently thymol is used as fungal repellent in several museums worldwide. Thymol is a reported decolorizing (foxing) agent and also harmful for human health (toxicity category-III). In the present study it has been observed that thymol is being used to conserve about three thousand rare documents belonging to Nobel Laureate poet Ranindranath Tagore and his ancestrals in Jorasanko Museum, India. The objective of our study was to promote a suitable nontoxic alternative for long term conservation of museum materials. Eucalyptus oil was selected for this purpose. Percentage Mycelial Inhibition (PMI) had been studied using 24 ppm, 48 ppm, 72 ppm and 96 ppm of eucalyptus oil on ten fungi isolated from the strong room of the museum. Both thymol and eucalyptus oil had been fumigated and fungal counts were observed after two days. Principal component analysis (PCA) revealed that 48 ppm eucalyptus oil and 4 days fumigation frequency yield optimum fungal control. It was sensitive for individual strains like Aspergillus tamari (32% removal) and Trichoderma sp (64% removal) which was not controlled by thymol fumigation. This study revealed that eucalyptus oil has better potentiality and can be used for long-term conservation of museum objects in future.