To investigate the potential spreading of leaded dust over Paris and its inhabitants, following the fire of Notre-Dame de Paris cathedral in April 2019, we developed a dedicated protocol to identify the geochemical fingerprint of the emitted particles. This method could be transposed to a contemporary monument to Notre-Dame de Paris which had not burnt and which had to undergo a major restoration phase: Sainte-Chapelle de Paris. Thus, a new study was performed on the indoor dust collected in this monument, to which the protocol developed for the dusts of Notre-Dame was applied. The comparison of the geochemical fingerprint of both monuments highlights the complexity of establishing the chemical signatures of such buildings. The homogeneity of the isotopic and elemental results obtained on the samples from Notre-Dame de Paris compared to those from Sainte-Chapelle de Paris reveals the homogenizing role of the fire, which simplifies the geochemical signature determination. Moreover, this study does not show any significant impact of anthropogenic pollution (road traffic, industry, incinerators) on the indoor environment of monuments, which are nevertheless rich in construction lead. The notion of “polluter-polluted monument" could be problematic in the event of an accident during restoration phase. These new results obtained on dust samples from a building that has not experienced any recent major deterioration underlines the multiple sources of lead present in these monuments and the importance of identifying univocally their signature. However, the concentrations of metal and metalloid in the indoor dust do not show any major pollution inside Sainte-Chapelle de Paris that could be a threat to human health.