Abstract: A scan head assembly for use in an imaging device for scanning media that uses fluid particles from the atmosphere for cooling an optical system, cleaning existing contamination particles in the scan head assembly and preventing contamination particles from accruing in the scan head assembly. The scan head assembly is enclosed in a chamber housing having an inlet in fluid communication with the scan head assembly and atmosphere. The scan head assembly has an optical system and a cooling mechanism located adjacent to the inlet. During use, the cooling mechanism directs fluid particles from the atmosphere through the inlet across the scan head assembly to provide cooling and cleaning to the scan head assembly, including the optical system. A negative pressure system is created within the scan head assembly to prevent contamination particles from accruing in the optical system.