Safety bulletins are used to alert industry to specific issues. They can be prompted by an accident, near miss or a discovery during survey/testing etc. They may refer to current guidance (e.g. SOLAS, MGNs. MSNs etc), or an alert to a new hazard that has just arisen for which there are no regulations or rules yet. They tend to be time sensitive and an action in response to usually required.
Current safety bulletin 20 is available to download via the link below, with previous bulletins also being available.