Most designs incorporate a pressure-balance duct linking the top of the float bowl with either the intake to the carburetor or the outside air.
If it is done by venting to the outside, the result is direct hydrocarbon pollution and an effective loss of fuel efficiency and possibly a fuel-odor problem.
A vapor lock can also develop when the engine is stopped while hot and the vehicle is parked for a short period.
The fuel in the line near the engine does not move and can thus heat up sufficiently to form a vapor lock.
[citation needed] In addition, aircraft are far more susceptible because of their ability to change altitude and associated ambient pressure rapidly.
With the introduction of the fuel injection requirement for NASCAR-sanctioned events in 2012, vapor lock has been largely eliminated.
However, it is not entirely unlikely to happen, as the double Red Bull Racing retirements at the 2022 Bahrain Grand Prix were caused by vapor lock, presumably due to the unusually high temperatures in the fuel system.
Air locks are eliminated by turning the engine over for a time using the starter motor, or by bleeding the fuel system.
Modern diesel injection systems have self-bleeding electric pumps which eliminate the air lock problem.