An environmental chamber that can be used to test a device under test such as a hard disk drive. The environmental chamber may include an electronically controlled shutter that controls the flow of controlled particles from a second chamber to a first chamber. The controlled particles flow to a device under the test located within the first chamber. The shutter can be closed when a predetermined threshold of contaminants is detected by the environmental chamber. This two-chamber method provides a stable and uniform density of particle environment around the drive.