If you've ever blown up a balloon, you have a rough idea of how air compressors work – hold a bunch of air, then force it out into whatever you need to inflate. The difference, of course, is in the compression: by squeezing a large amount of air into a small storage space, an air compressor can then release a very powerful wind. Beyond just inflating things, this can also be used to power pneumatic equipment.
When you're thinking of buying a compressor for home use, there are a number of qualities to consider, depending on the type of work you're going to be using it for.
Single-Stage or Two-Stage
The number of stages refers to how many cylinders the compressor has – a two-stage compressor forces the air through one cylinder and then further compresses it through a second. This allows it to deliver air at a higher PSI (pounds per square inch), making them a good choice for heavy-duty use or powering more than one tool at once.
Stationary or Portable
If you have a garage or workshop where you will be doing all the work that requires a compressor, then you should consider having a stationary compressor installed; they are generally larger and more powerful than portable units.
However, most people want a home compressor to be more versatile – if you want to be able to use your compressor to power a nail gun in the garage as well as inflate a tire in the driveway or a sander in the backyard, choose a portable model. They come in a variety of sizes and air flows – check the requirements for the tools you plan to use to make sure you purchase a sufficiently powerful model.
A good rule of thumb is to find the tool that will require the highest CFM (cubic feet per minute) of air at the highest PSI from the tools you're planning on using. Make sure that your compressor delivers at least 150% of that CFM at at least 100% of that PSI to give yourself a safety margin.
Gasoline or Electric
The type of power you should choose depends largely on where you're going to be using your compressor. Gasoline compressors shouldn't be used in unventilated areas, so while they are a fine choice for outdoors, they aren't the best choice for a garage. You will need one if you're going to be doing work where electricity isn't available, however, like if you need to take your compressor to various job sites. For home use, electric compressors are usually sufficient; with extension cords, they can be used in most areas relatively easily.
There are also some extra compressor features that can make your life a little easier. A compressor with multiple couplers will allow you to use multiple tools without needing to constantly disconnect and reconnect them. An oil-free pump is lighter and requires less maintenance than an oil-lubricated one. A thermal overload switch can automatically turn off the compressor if it detects an overheated motor, while an air-cooling system can help the motor run cooler for longer. And be sure to check what accessories come with your compressor and which you will have to purchase separately. Talk with a retailer, like http://www.benscleaner.com, to find the air compressor that's right for your projects.