A “safety can” is an approved container of not more than 5-gallon (19 L) capacity having a spring-closing lid and spout cover so designed that it will relieve internal pressure when
subjected to fire exposure. Safety cans are commonly used where limited quantities of flammable and combustible liquids are required for manufacturing or research. The basic
purpose of a safety can is to provide a safe and convenient means of transporting, dispensing and storing up to 5 gallons (19 L) of flammable and combustible liquids. All listed safety cans, regardless of the material of construction, are required to be constructed as leak tight containers. They must automatically vent any vapor if subjected to fire exposure at a pressure of 3 to 5 psig (20 685 to 34 475 kPa gauge) to prevent the container from being subjected to a deflagration resulting from the increased vapor pressure of the liquid.
Openings on safety cans must close automatically after being filled or dispensing a liquid. Finally, all listed safety cans must be designed so that a two-dimensional fire that could occur during dispensing cannot reach the pour opening and potentially extend into the safety can. This is commonly prevented by installing a flame arrestor in the container’s inlet and outlet openings.
UL (Underwriters Laboratories) lists safety cans using UL 30 for metallic cans and UL 1313 for nonmetallic cans. Factory Mutual (FM) Global also issues listings and approvals for metallic and nonmetallic safety cans. UL and FM both limit the volume of metallic safety cans to 5 gallons (19 L) or less—nonmetallic safety cans are permitted to have a volume
of 6.6 gallons (25 L). UL assigns a designation to safety cans based on the number of openings at the top of the container and container appurtenances.
A Type I safety can is commonly a single-spout can design for filling containers or tanks with large receiving openings.
A Type II safety can have an integral flexible dispensing hose to control the transfer of the liquid. These safety cans have a second opening that serves as a pressure-
vacuum vent which is also used to fill the safety can with liquid.