IR windows are gaining acceptance as an alternative to opening high voltage electrical cabinets. There are two basic types of windows. Clear windows and grills (with or without integrated windows) are offered and each is designed for specific applications. When using an infrared window, be sure to add a wide angle lens to your infrared camera, typically 50°. This will enable you to focus on objects close-up while viewing a larger area within the cabinet reducing the number of windows that may be needed. When working with grill type windows be sure to attempt to maintain a perpendicular view through the window because as you increase the viewing angle the percentage of the grill that is clear gets smaller as the effective area of the actual grill material increases leading to lower and lower effective transmission and increased measurement error and thermal sensitivity.