According to API 510, what must be done before any inspector enters a pressure vessel for internal inspection?
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A
The vessel must be isolated, depressurized, purged, and ventilated to ensure a safe atmosphere
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B
The vessel only needs to be cooled to ambient temperature before entry
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C
Reducing internal pressure to 15 psig is sufficient for safe entry
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D
The inspector may enter with supplied-air respirator without additional preparation