46 CFR §140.430

1. (a)Personnel dispatched from the vessel or that are working in an area on the exterior of the vessel without rails and guards must wear a lifejacket meeting requirements in 46 CFR 141.340, an immersion suit meeting requirements in 46 CFR 141.350, or a work vest approved by the Commandant under 46 CFR subpart 160.053. When worn at night, the work vest must be equipped with a light that meets the requirements of 46 CFR 141.340(g)(1). Work vests may not be substituted for the lifejackets required by 46 CFR part 141.
2. (b)Each storage container containing a work vest must be marked “WORK VEST”.