<https://astragroupuk.com/how-to-select-a-cleanroom-luminaire/ip-rating/#webpage>
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"Cleanroom luminaires are generally recessed in to the ceiling and as such form part of the cleanroom shell, hence the IP rating of the luminaire is critical to maintaining the integrity of the room. Cleanroom luminaires are given a dual IP rating, one rating with the front frame diffuser in position and another for when..."
<https://astragroupuk.com/how-to-select-a-cleanroom-luminaire/ip-rating/>