With the continuous shrinkage of critical sizes in semiconductor manufacturing, nano-particles smaller than 100-nm are becoming a potential threat to devices in chips. Storage of wafers contaminated during process steps often results in a decrease of particle removal efficiency in subsequent clean, a phenomenon referred to as aging. In this work, the influence of aging on the removal of silica and silicon nitride nano-particles from hydrophilic Si wafers was studied for different storage conditions. Trends observed for aging as a function of particle size and for different tools indicated that aging will become an issue for critical cleans where substrate etching must be kept very low and the physical component of the clean must be decreased to prevent damage to fine structures. Controlling the relative humidity during storage helped in lowering the effect of aging.