Infrared (IR) Viewports are a fixed aperture@ consisting of one or more openings or a solid infrared transmitting media@ surrounded by a mounting bezel or frame@ that provide a means for the passage of infrared radiation. Infrared viewports are intended for factory installation in doors or walls of electrical enclosures for installation in ordinary (non-hazardous) locations to allow the use of IR scanners for monitoring temperatures of the enclosed equipment on which the viewport is installed@ without compromising the integrity of the enclosure with respect to access to live parts. Viewports may be investigated for installation in Type 1 enclosures or enclosures with other environmental ratings. Compliance with these requirements does not assure that the infrared viewport is suitable for use as a component of an end product. For example@ accessibility of live parts is investigated with respect to industrial products rated 600 V and below@ and additional investigation may be required for products rated over 600 V. The acceptability of an infrared viewport in any particular application depends upon its suitability for continued use under the conditions that prevail in actual service. Accordingly@ for a particular application an infrared viewport may be affected by the requirements for the equipment in which it is used@ and it may be necessary to additionally evaluate that infrared viewport for features or performance characteristics that are not specified in this Outline of Investigation. 1.4 These requirements do not cover the field installation of infrared viewports on enclosures of electrical equipment already in service. These requirements do not cover viewports made from glass or translucent polymeric materials intended for passage of visible light for observation of internal electrical equipment by operators or service personnel.