“What is the difference between a single-stage and dual-stage air compressor?” That’s a question many people ask when shopping for a compressor.
Air compressors come in two types: single-stage and dual-stage. The primary difference between the two is the number of times air gets compressed on the trip between being uncompressed outside air and being compressed air in the storage tank. In a single-stage compressor the air is compressed once and sent to the storage tank. In a dual-stage compressor the air is compressed twice and then sent to the storage tank.
Single-stage compressors work similar to the engine in your car. When the piston moves down the air is sucked into the cylinder. When the piston moves up it compresses the air to somewhere around 120 PSI. The compressed air is then sent to the storage tank. The compressed air is stored in the tank for later use powering your air tools.
A dual-stage compressor works the same way except that after the air is compressed in the first cylinder, then, instead of being sent to the storage tank, it is sent to a second, smaller cylinder that compresses the already-compressed air even further to somewhere around 175 PSI. Air heats up when it is compressed so there is usually some cooling before the air is sent to the storage tank. Again, the compressed air is stored in the tank for later use powering your air tools.
Most air compressors have two cylinders—that is not to be confused with being a dual-stage compressor. Compressors usually have two cylinders for the simple reason that it’s easier to balance the air. In a single-stage compressor, both cylinders are the same size. In a dual-stage compressor, the second cylinder is smaller than the first and the two cylinders are connected by a cooling tube to cool the air before the second compression.
So which one to choose? Dual-stage compressors provide higher pressure making them better for large-scale and/or continuous air tool operation. The down side is that dual-stage compressors often cost more which makes them less attractive for occasional use at home. If you are running a factory or shop with a lot of air-powered tools and machinery, you usually want a dual-stage compressor. For home use where you usually only use one tool at a time, a single-stage compressor might be a better choice because it’s not as expensive, but it will still meet your air pressure and air flow needs.
Air tools—actually, the documentation that comes with air tools that you probably threw in the trash shortly after purchase—indicate the air pressure (PSI) the tool should be operated at and the cubic feet per minute (CFM) air consumption required to maintain that pressure during usage. Compare the air requirements of your most air-intensive tool, or the most air-intensive tool you plan on buying in the future, to the output of the air compressor you want to buy. If you can’t find the requirements for your specific tool, search online for a comparable tool—the requirements should be similar.
Some popular hobby air compressors are the Badger TC908 Aspire (0.81 CFM @ 40 PSI), the Paasche D3000R (0.5 CFM @ 30 PSI), the Iwata IS-850 Smart Jet (0.64 CFM @ 35 PSI), and the Iwata IS-30 Ninja Jet (0.30 CFM@ 18 PSI). All of them put out less than 1.0 CFM and they all have fairly low maximum pressures. Just about any air compressor you want to use will be adequate for airbrushing and other modeling uses, whether single-stage or dual-stage.