Films containing nitrocellulose, which is susceptible to spontaneous combustion, famously pose a considerable risk of fire. Part of the responsibility of the photo archive of the library of the Eidgenössische Technische Hochschule (ETH) in Zurich is therefore minimizing the risk posed by nitrocellulose films in its stacks. The precondition of such measures is identifying the amount of nitrocellulose film in each item. Using the SurveNIR system by the firm Lichtblau e. K. in Dresden, the material of 35,109 samples was identified in a fifteen-month period and the state of their aging studied. That amounts to 1.36 % of the estimated total holdings. Along with visually recording typical damage in photographs, it provided an objective, extensive database for conservation and preservation methods for the next ten years.