## 1 Introduction
The antifungal activity was determined by the dilution method and the vapor phase assay. The results confirmed that the EO vapor phase exhibited long-lasting suppressive activity on fungal growth and that thyme EO possesses a wide range spectrum of fungicidal activity, as was also reported by [PERSON] et al. [20]. [PERSON] et al. [21] tested the antifungal activity of 20 EOs against _Alternaria alternata_, _Stachybotrys chartarum_, _Cladosporium cladosporoides_ and _Aspergillus niger_. The results obtained evidenced that _Origanum vulgare_, _Pimenta racemosa_, and _Thymus vulgaris_, EOs with a high content of thymol, carvacrol, or eugenol, had the highest antifungal effects and the lowest MIC values. Regarding the toxicity of _O. vulgare_ and _T. vulgaris_ EOs, [PERSON] et al. [22], by means of the in vitro haemolytic assay, demonstrated that thymol and carvacrol are significantly less cytotoxic than conventional antifungals. Moreover, they are quickly metabolized and excreted in human and animals, thus providing a very promising \"safe\" alternative in the field of antifungal applications. Over the past 20 years, different EOs and their main constituents were investigated as antimicrobial agents for control of biodeterogenic microorganismsin archives and libraries; in particular, the research focused on the antifungal activity in vapor phase, evaluated at laboratory scale by means of micro-atmosphere method (MAM). [PERSON] et al. [23] studied the antifungal activity of nine EOs and five of their main constituents against a mixture of fungal strains isolated from historical archives. The MAM, in Petri dishes, was applied as a preliminary screening to obtain the Minimum Fungicidal Concentration (MFC) value; after that, the experiment was carried out in a test chamber with a larger volume. Paper sheets, inoculated with the fungi, were inserted in a book and the EOs were arranged at the bottom of the chamber for 21 days, in controlled conditions of temperature and humidity. In the last case, the linalool oil had only a fungistatic effect rather than a fungicidal one as observed in Petri dishes. Among the different tested EOs, tea tree and lavender ones and their main components, eugenol and linalool, were particularly active in inhibiting fungal strain growth. In the work of [PERSON] et al. [24], MAM was used to evaluate the biocidal activity of _O. vulgar_ and _T. vulgaris_ EOs against _Scopularis_ sp. and _Fusarium_ sp., isolated from documentary heritage. The EOs tested showed a high level of activity against both fungal isolates and a low environmental impact. [PERSON] et al. [20] also underlined that EO treatments of archival materials must ensure safety of treated goods and personnel along with treatment efficacy. The use of oregano EOs' volatile compounds against oil painting biodeteriogens [25] was proposed as innovative and eco-friendly cleaning method. The aim of the present work was to gather information about the possibility to apply red thyme EO in a library, mainly contaminated by filamentous fungi. To this end, the fungus _Alternaria alternata_, used as a model of paper biodeteriogens, was treated with _Thymus vulgaris_ oil in vapor phase. The MAM in Petri dishes was used as preliminary screening, the treatment was then scaled up in an airtight container to test the influence of different evaporation rate on MID value.