I don’t know the SMS of individual Norwegian shipping companies as I haven’t sailed on Norwegian flag ships since 1970.
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As for the Chemical tanker companies you mention I would assume they follow IMO Recommendations for this (and other subject):
Since they have ships under many different flags the SMS for individual vessels MAY have to differ to comply with flag state rules though.
PS> I couldn’t find any specific rules, regulations or guidelines from NMA re: confined space entry on NOR or NIS registered ships. (IMO recommendation apply)