Within an evaporative emission control system, a charcoal canister vent control valve prevents gasoline vapor emissions from escaping into the atmosphere. The Environmental Protection Agency requires that all new cars be equipped with these EVAP systems.
Gasoline fumes contain a high level of hydrocarbon gases, which are harmful to the atmosphere. Hydrocarbon gas molecules are highly reactive; they damage the ozone layer by bonding with its molecules. The ozone layer protects the Earth from harmful ultraviolet rays from the sun. Its depletion results in increased surface temperature on the planet and a higher risk of UV-related illnesses among its inhabitants.