Infrared windows are IR transmissive viewing-port inspection devices designed for enclosure integration. They are used for real-time visual monitoring of infrared (IR) light produced by a variety of heat-generating sources. Infrared windows consist of special panes of transparent, infrared material set in a frame. The transparent IR window material allows thermal imaging of the component inside the electrical enclosure or equipment.

Different materials for infrared windows are selected depending on the wavelength observed.  Infrared light can consist of near IR (NIR), short wavelength (SWIR), mid wavelength (MWIR), long wavelength (LWIR), and far infrared (FIR).  Common infrared transmitting materials for infrared windows include calcium fluoride, barium fluoride, zinc selenide, infrared polymer, zinc selenide, germanium, sapphire or single crystal alumina, spinel (magnesium aluminate, MgAl2O4), and yttria.

IR windows are most commonly used in thermography or infrared imaging applications for the detection of hot spots. Hot spots may occur due to electrical failures; faults; or thermal leakage in electrical distribution equipment, circuit breakers, switches, switchboards, switchgear, transformers, motor control centers, and generators; and in junction boxes, panel boards, furnaces, ovens, and process equipment.

Thermographers or thermal imaging inspectors have specialized training to perform analysis correctly and help manufacturers comply with NFPA70E, CSA Z462, and OSHA CFR 1910 standards. Thermography is an important tool in the predictive maintenance tool kit, which means that IR windows may also be used for process protection, blocking airflow, cooling of heated surfaces, and UV blocking.

Infrared windows may have the option of having protective shields, screens, or perforated sheet reinforcements. These allow IR light to pass through, while protecting the window and operators against breakage or shattering from an explosion or arc flash. Specialized infrared windows are made of non-conductive materials, and may also have a cover to close the window and block IR transmission.

IR windows can be manufactured to meet several industrial standards or approvals such as Lloyds Type Approved, Nuclear Mutual Limited (NML) testing, and UL and ULc certification; all of which are fabricated to a UL94 5VA requirements. Additional IR window standards include UL746, IEEE C37.20.2, IP2X, NFPA 70E, UL 508A and 746C for flammability and impact resistance, IP65, and NEMA 4.