Canister purge valves are located between the fuel tank and the engine and are often placed in or on the throttle bay in models of car from the 1990s, 2000s and 2010s. In models from the 1970s and 1980s, the valve is in the engine bay.
Underneath the hood of a car, parts are organized into bays. These are compartments that separate parts into units. For example, the engine bay contains all the components of the engine, plus the radiator, thermostat, driveshaft and parts relating to the transmission. The throttle bay is a separate compartment that contains an air filter box, pressure regulators and the fuel injection apparatus.
Canister purge valves prevent fuel tank fumes from entering the atmosphere, so by necessity they are always located between the engine and tank. They have been standard in cars since the mid-1970s. Past the 1980s, they are most commonly found in the throttle bay, but in the earliest models, they were attached to the canister assembly in a corner of the engine bay. Exact location varies by make and model of car.