An air compressor is one of the most useful tools to own. Air compressors can be used for more than inflating tires. In fact, this device can power nail guns, spray guns, wrenches and many other tools.
When shopping for air compressors, you'll come across two basic types:
1. Single-stage compressors have one piston that compresses and delivers air to the storage tank. The single-stage system is normally found on light-duty compressors with a maximum rating below 150 pounds of pressure per square inch (psi). Single-stage compressors are adequate for most home users.
2. Two-stage compressors have two pistons that compress and deliver air to the storage tank. The first piston compresses the air and pushes it through a check valve to the second piston. The second piston further compresses the air and delivers it to the storage tank. The two-stage system is usually found on commercial heavy-duty compressors with maximum ratings above 150 psi. Two-stage compressors are good choices for continuous use or shop environments.
Horsepower ratings are a measure of the horsepower (HP) the compressor motor produces. Compressor motors generally range from 1.5 HP to 6.5 HP. More powerful units are available for industrial applications. Usually higher horsepower motors yield greater psi and are capable of carrying a heavier workload.
Compressor storage tanks are rated in gallons. Larger tanks store more compressed air at higher pressures. The amount of air a compressor delivers is measured in cubic feet per minute (CFM). Note that the CFM a compressor delivers changes at varying psi. Most air tools have specific requirements for volume and pressure. These requirements must be met for the tool to function properly. When choosing a compressor, consider the tools you want it to operate. Select the tool that requires the highest CFM at the highest psi, and add 50% to the required CFM for a margin of safety. For example, if a tool requires 3 CFM at 90 psi, select a compressor that delivers at least 4.5 CFM at 90 psi. Use this formula to ensure that the tool receives enough air to function properly.