How can a crystal or polymer optic withstand an arc flash?

No infrared window on the market can protect a worker if an arc flash occurs during inspection.  Actually, there is no standard for arc resistant infrared windows.

Then what is an “arc resistant IR window”?

While some manufacturers claim that they make an “arc resistant IR window” after taking part in a test outlined in the ANSI/IEEE C37.20.7, EIC 298, and IEC 62271-200 standards for performing arc fault testing on switchgear.  However, the standards clearly state the intention to apply arc resistance to the entire system that is tested, not individual components such as the IR window.

Why use an IR Window?

Infrared windows provide a safer, more efficient environment in which thermographers can image energised electrical conductors while keeping the enclosure closed. They eliminate the high risk practices that may cause an arc flash, as well as enabling companies to comply with regulatory requirements and insurance mandates.

Crystal vs Polymer?

In the IR window market, there are two “types” of optic: crystal and polymer.

Crystal optics were designed in the early days of thermography, when thermal cameras were large, expensive and fragile.  The market has since evolved, and thermal cameras can now fit on a mobile phone, they are rugged and a fraction of the price that they were in those early days.  Optics are similar.  The new polymer optics are considerably more impact resistant than their crystal counterparts, they can be cut to any shape to allow maximum view ability of the target, and provide superior transmission rates and stability. Additionally, a polymer optic is more cost effective than a crystal one.