Issues regarding the classification of explosion-proof zones around flanges and valves in hydrogen pipelines

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Hello everyone, I have a question. First, let me explain the situation on site. There are hydrogen pipelines in the plant, one 2-inch and one 1-inch, with relatively long routes. There are some branch circuits that branch off from the main line; flanges and valves are available at these branching points to switch the branch circuits on and off. At this flange and valve, a hydrogen sensor is installed to detect any hydrogen leaks. The sensor is then enclosed in a square box made of transparent acrylic, and an exhaust pipe from the ventilation system is used to draw air into the box, ensuring that any leaks are removed. The question now is: with it wrapped up in this way, and with the flanges and valves in that area being under vacuum, does it still count as an explosion-proof zone? In accordance with the requirements for hydrogen explosion prevention, do electrical devices such as lighting fixtures in the surrounding area also need to be explosion-proof? Are there any relevant standards? If so, what is the radius around the hydrogen pipeline considered the explosion-proof area? Thank you.