ATEX Rating?

"Atmospheres Explosibles". ATEX is a safety standard given to a certain component(s) for use in a potentially explosive atmosphere. ATEX rated components may have a hazardous area certification for one of the following: explosion-proof, flame proof, intrinsically safe, or non-incendive. This rating can be found on something electrical such as a fan, fuse, motor, circuit breaker, or an encoder to something non-electrical such as an enclosure.

See also:
https://www.csagroupuk.org/?s=atex
https://www.csagroupuk.org/services/ex-product-certification-approvals/atex/
http://www.beisensors.com/hazardous-area-encoders.html#hazardous_area_certified