When shopping for this kind of item, it is important to understand how it works and what the typical uses are for the machine. An air compressor simply takes a volume of gas (from the atmosphere) and packs it into a smaller space, thereby building up pressure in a self contained tank. This means that the contents will freely flow out once a valve is opened, since the pressure inside the canister is greater than the air outside. This is what makes it perfect for a great variety of applications.
This includes putting air into car tires, blowing off a work bench or painting a wall. All of these items can be easily accomplished through the use of an air compressor and some simple attachments.
The units for this machine are measured in psi (or pounds per square inch), with the higher the number, the greater volume of gas is contained in the cylinder. It can be adjusted to shut off when reaching a preset value and many models can be connected to a valve to dial down the pressure as well.