An apparatus and associated method for enclosing an environment-sensitive component. An enclosure separates an interior environment inside the enclosure from an external environment outside the enclosure. The enclosure has an environmental control system that captures a contaminant from the internal environment to a filter via a first diffusion path, and captures the contaminant from the external environment to the same filter via a different second diffusion path, the diffusion paths providing substantially different flow resistances to fluids carrying the contaminants to the filter via the respective diffusion paths.