Air compressors can be found at virtually every jobsite and workshop. They play a versatile role, powering pneumatic tools like nail guns, impact wrenches and angle grinders, and they are indispensable for inflating vehicle tires. To pick the right air compressor, think first about how you will use it.
If you plan to use an air compressor for interior jobs, like nailing trim carpentry, you might choose a lightweight electric compressor that can move with you throughout the building. If you’re going to be painting vehicles with a pneumatic paint sprayer, you’ll want a high-output compressor that stays in the shop. And if you’re working on outdoor job sites that lack electrical power, you’ll need a gasoline-powered compressor.
Here are some other considerations for selecting the right air compressor for the job.
If you just need a tool to air up your car’s tires, an inflator is ideal. An inflator is an air pump that has no reservoir—instead of storing compressed air in a tank, it delivers high-pressure air directly to vehicle tires or sporting equipment. Inflators are portable and cheap, perfect for filling tires but inadequate for running pneumatic tools.
An air compressor fills an attached storage tank with high-pressure air, which passes through a regulator as it flows from the tank and into a hose. This allows air compressors to deliver a steady stream of air to power pneumatic tools.
A stand-alone tank can give your compressor greater versatility. For example, if you need a large stationary air compressor to run pneumatic paint tools in your shop, a 20-gallon wheeled tank can enable you to transport compressed air to a small job outside the shop without the expense of buying a second, portable air compressor.
Pneumatic tools have a wide range of air supply demands. A trim nailer or a pneumatic staple gun might require less than a single cubic foot per minute (cfm), while an air excavation gun can use over 300 cfm. Common shop tools like pneumatic impact wrenches and angle grinders will draw between five and 10 cfm.
Air compressors are rated in cfm, and you want to choose one that can match your tool’s needs. Since the compressor’s tank stores a reservoir of compressed air, you can briefly run a tool that draws more airflow than your compressor can supply. For a tool that is only in use sporadically, like an impact wrench, relying on the reservoir may not be a problem. But if you’re constantly using more volume than your compressor can supply, you will have to take regular breaks to allow your compressor to make up the deficit.
Air compressors can be powered by either an electric motor or a small gasoline engine. Electric compressors are cheaper, since their motors are simpler, but they have two major disadvantages: first, you need a power supply, which isn’t available at every jobsite. Second, a standard 120-volt electrical outlet cannot provide more than 2.5 horsepower, which limits the volume of air the compressor can supply. Electric compressors that run on 240 or 460 volts are much more powerful, but you’ll need the right wiring setup to use them.
Gasoline engine compressors are more powerful and can run anywhere outdoors. Aside from cost, the primary drawback of a gasoline engine is that it is noisy, and its exhaust fumes make it unsuitable for indoor work spaces.
The smallest, lightest air compressors can be hand-carried. They have less powerful motors and smaller tanks, but you can bring them to almost any workspace. Compressors with more powerful motors and larger tanks are too heavy to carry, so they have wheelbarrow-style handles and can be rolled into position. Wheeled compressors are still portable, but they can be difficult to bring up stairs.
The largest, most powerful air compressors are not mobile at all. Large gas-powered compressors are intended to be mounted permanently to a truck bed, which means the job must always be a hose-length from a parking space. And the largest electric compressors are designed for permanent installation in a shop.
The right compressor will be able to supply as much air as you need, where you need it. If you’re stapling insulation to your home’s rafters, you may want a compressor you can pick up and carry up a ladder. If you’re using air wrenches and paint guns in your garage, a high-cfm, stationary compressor would be best.
Air compressors have an attached tank that acts as a reservoir of compressed air, allowing them to deliver steady airflow to your tools. While the volume of air entering the tank must eventually match the volume of air flowing out, a large reservoir will allow you to intermittently use tools with high airflow requirements. The volume a compressor can store in reserve depends on two factors:
Tank Size: The tanks on portable compressors run from two to 30 gallons, and many stationary compressors feature tanks over 100 gallons. A gallon is 7.48 cubic feet, so a five-gallon tank holds enough air to run a typical framing nail gun for 10 to 15 minutes.
Storage Pressure: Most pneumatic tools are designed to run on air compressed to 70-90 psi (pounds per square inch). But an air compressor fills a tank, rather than directly powering tools. It can run at higher pressure, from 100 to 175 psi. And the higher pressure it can deliver to the tank, the more spare capacity you’ll have in reserve. The tank’s regulator will step down the air pressure to an appropriate level for the tool you’re using.
The amount of reserve air you need will depend on the tools you’re using and the type of work you’ll be doing. A larger reservoir isn’t necessarily better: high-pressure compressors cost more, and large tanks are heavy to haul around. If you’re a commercial contractor and time is money, it may be worth investing in a large tank and a high-pressure compressor so work never has to stop. But a home handyman working in the attic may decide that a two-gallon tank that’s easy to carry up a ladder is ideal, even if it means taking an occasional break while the reservoir refills.
Tank Shape: Compressor tanks come in a variety of styles. Portable air compressors that you can carry often have a compact “pancake” shaped tank, while many wheeled compressors have long, narrow “hot dog”-shaped tanks. Stationary compressors typically have cylindrical tanks, either mounted horizontally for stability, or vertically for a compact footprint. The best tank shape will depend on your requirements for portability and the storage space you have available.
Sound Level: Air compressors are inherently loud. The quietest electric compressors produce about 60 decibels, making them as loud as a busy restaurant. The loudest electric compressors reach 86 decibels, and they can be difficult to talk over. Several gas-powered compressors exceed 90 decibels, about as loud as a lawnmower. A quieter compressor may create a more comfortable—and communicative—working environment.
Lubrication: Many electric compressors use oil to lubricate the piston that compresses air. Oil-free compressors use permanent friction-reducing materials instead of oil. If you choose an oil-lubricated compressor, be aware that you will need to periodically refill the oil reservoir.
Generator Combos: Since gas-powered air compressors are often used at job sites that lack electrical power, several models include a built-in electrical generator to provide power for lighting and other tools. Combination compressor-generators make dual use of the gasoline engine, saving space and money.
For more information about air compressors and pneumatic tools, visit Grainger.com.
The information contained in this article is intended for general information purposes only and is based on information available as of the initial date of publication. No representation is made that the information or references are complete or remain current. This article is not a substitute for review of current applicable government regulations, industry standards, or other standards specific to your business and/or activities and should not be construed as legal advice or opinion. Readers with specific questions should refer to the applicable standards or consult with an attorney.
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