A method for detecting fungal contamination of indoor surroundings defined by a confined space inside a building which is not continuously aerated which comprises the following stages: a. withdrawing a sample of volatile organic compounds (VOCs) in indoor surroundings, b. detecting the presence or the absence of certain predetermined VOCs resulting from fungal metabolism, these predetermined VOCs comprising at least one VOC of each of the three following categories of VOCs: the VOCs which are given off independently of the fungal species and of its substrate and which are given off only by fungal species; the VOCs which are given off independently of the fungal species and of the substrate but which can also have other biological origins; the VOCs which are given off according to the fungal species and/or substrate; c. calculating a chemical index for fungal contamination according respectively to the presence and absence of the predefined VOCs resulting from fungal metabolism, taking into account that: the presence of VOCs of category directly indicates the presence of fungal contamination, while the absence of such VOCs indicates the absence of fungal contamination; the presence of VOCs of category does not allow it to be concluded that fungal contamination is present while the absence of such VOCs indicates the absence of fungal contamination; and the presence of VOCs of category indicates the presence of fungal contamination while their absence does not allow it to be concluded that fungal contamination is absent. a. withdrawing a sample of volatile organic compounds (VOCs) in indoor surroundings, b. detecting the presence or the absence of certain predetermined VOCs resulting from fungal metabolism, these predetermined VOCs comprising at least one VOC of each of the three following categories of VOCs: the VOCs which are given off independently of the fungal species and of its substrate and which are given off only by fungal species; the VOCs which are given off independently of the fungal species and of the substrate but which can also have other biological origins; the VOCs which are given off according to the fungal species and/or substrate; the VOCs which are given off independently of the fungal species and of its substrate and which are given off only by fungal species; the VOCs which are given off independently of the fungal species and of the substrate but which can also have other biological origins; the VOCs which are given off according to the fungal species and/or substrate; c. calculating a chemical index for fungal contamination according respectively to the presence and absence of the predefined VOCs resulting from fungal metabolism, taking into account that: the presence of VOCs of category directly indicates the presence of fungal contamination, while the absence of such VOCs indicates the absence of fungal contamination; the presence of VOCs of category does not allow it to be concluded that fungal contamination is present while the absence of such VOCs indicates the absence of fungal contamination; and the presence of VOCs of category indicates the presence of fungal contamination while their absence does not allow it to be concluded that fungal contamination is absent. the presence of VOCs of category directly indicates the presence of fungal contamination, while the absence of such VOCs indicates the absence of fungal contamination; the presence of VOCs of category does not allow it to be concluded that fungal contamination is present while the absence of such VOCs indicates the absence of fungal contamination; and the presence of VOCs of category indicates the presence of fungal contamination while their absence does not allow it to be concluded that fungal contamination is absent.