Electrical devices that are safe in your house could prove disastrous in a more flammable environment, such as might occur onboard a marine vessel. Devices that are compliant with the International Organization for Standardization (ISO) 8846 marine standards have been tested to ensure their safe operation onboard small marine craft.
ISO 8846 marine standards were designed to set guidelines for devices used on small marine craft, where the atmosphere can contain high concentrations of flammable gases. Standard testing for electrical devices considers normal operating conditions and gas concentrations such as might be found in a house, such testing was not adequate for marine environments.
ISO 8846 was published in 1990. As with other, small craft safety standards, responsibility for ISO 8846 marine standards lies with the small craft technical secretariat, the German Institute for Standardization (DIN).
You can access the ISO 8846 marine standard from either ISO or your national member organization (in the U.S., it is the American National Standards Institute, ANSI). Copies are available for download, but they must be purchased; members of national representative organizations might qualify for discounted standards.