Ships subject to the Chapter IV of the Safety of Life at Sea (SOLAS) Convention have to fit GMDSS equipment. These include all ships engaged on international voyages except:
- Cargo ships less than 300 gross tonnage,
- Ships of war and troopships,
- Ships not propelled by mechanical means,
- Wooden ships of primitive build,
- Pleasure yachts not engaged in trade,
- Fishing vessels, and
- Ships being navigated within the Great Lakes of North America.
U.S. Communications Act Ships
Ships subject to Title II Part II and Part III of the Communications Act of 1934, as amended have to fit GMDSS equipment under FCC Regulation 47 CFR 80 Subpart W. These include all ships, including fishing vessels, to be navigated in the open sea outside of a harbor or port, except:
- Ships other than passenger vessels less than 300 gross tonnage,
- Passenger ships having six passengers or less,
- U.S. government ships,
- Yachts of less than 600 gross tons,
- Vessels in tow,
- Ships navigating solely on any bays, sounds, rivers or protected waters within the U.S.,
- Ships being navigated within the Great Lakes of North America, and
- Small passenger ships meeting the requirements of 47 CFR 80 Subpart S.
Note that on 20 November 1998, the FCC has waived certain GMDSS rules applicable to fishing vessels and small passenger vessels.
Mobile Offshore Drilling Units (MODUs)
Mobile Offshore Drilling Units have to fit GMDSS equipment if they are self propelled, or if they are required to meet the International Maritime Organization's MODU Code.