Dust accumulation is an important management and conservation problem in historic houses. Laboratory and field observations show that high relative humidity enhances the cementation of particles to underlying surfaces. The hygroscopic nature of particles or the fibres to which they adhere influences this cementation process. The cements, which can form in a matter of hours at high humidity, appear to be microcrystalline calcites. Reducing the impact of this process on heritage objects requires preventing dust deposits, especially in periods of high humidity.