An air germicidal treatment device and system for removing or eliminating unwanted pathogens or bacteria in an airstream is shown. The device or system has a removable irradiation chamber that divides an interior area of the device into an air pre-chamber area, an air post-chamber area and an irradiation area therebetween. The removable irradiation chamber is generally trapezoidal in shape and has end walls that are inclined with respect to an interior divider wall.