Selecting the best sizes and models of air compressors to distribute can't be that hard, right? All you have to figure out is about how much air most of your client base may need.

Unfortunately, you'll find it's not quite that easy once you start looking into it. There's psi, hp and CFM. And what about SCFM, DSFM and ACFM? Simplex or duplex? Single-stage or two-stage?

Relax. You already understand your client base. Now it's a matter of connecting the dots between compressor models and customers' applications.

Let's begin with the basics. Do most end users work in shops? Or, do they move from one jobsite to another? Portability is one of the first things to consider. Will a hand-carry or wheeled-portable model be best, or would the customer benefit from a larger stationary unit? Consider the compressor's weight, as well as the presence of wheels and handles if a portable machine is needed.

The typical jobsite also will affect the type of power source best suited for end users. If your customer tends to work in a remote area without access to electrical power, either from the grid or an on-site generator, the only choice is a gasoline engine model. This allows complete mobility both to and from the jobsite, as well as around the work area.

Environmental restrictions—such as emissions in a confined space or noise abatement—may cancel any benefit of a fuel-powered compressor, however. The gas model also will cost more up front to maintain over its service life. Contrarily, electric-motor counterparts do not provide as much horsepower as gas models.

Besides portability and power, capacity will directly affect what applications end users will be able to perform. To get an idea of your customer's size needs, add up the CFM (cubic feet per minute) requirements for all of the tools that likely will be used simultaneously in their field. Add an extra 30 percent to allow for unknown or uncommon compressor usage. CFM demands are listed on the tool and/or in the owner's manual.

Capacity, or volume—in other words, CFM—can be figured three ways. First, displaced CFM (DCFM) offers a mathematical calculation of bore, stroke and rpm. It doesn't, however, take into account any other variables, such as temperature, atmospheric pressure, humidity, friction or heat dissipation. In other words, it means little in the working world.

Standard CFM (SCFM) is a more realistic measure. It references the flow of free air in a standardized environment, such as 14.5 psi atmospheric pressure (the pressure at sea level), 68 degrees Fahrenheit and 0 percent humidity. Since this is a standardized metric, it's the best figure to use in comparing air compressors across the board.

The third way to calculate CFM is actual CFM (ACFM), which figures variables for a specific situation. If the majority of end users live in Anchorage, their ACFM needs would differ considerably from someone in Miami. These figures can be hard to get, however, and just as hard to calculate. For distributorship purposes, monitoring SCFM ratings will typically be the best option.

CFM also comes into the single-stage versus two-stage decision. What are the minimum operating pressures of the tools end users are most likely to use? Single-stage compressors work well up to 150 psi. For more pressure, a two-stage compressor will need to be used.

So what's the big difference? A single-stage compressor usually has a higher CFM rating because the cylinder draws in air and compresses it with every rotation. A two-stage unit compresses the air up to an intermediate pressure in one or more cylinders and then passes it on to another cylinder to finish. This passage, which is usually to an intercooler between stages, makes a two-stage compressor more efficient at high pressures.

The end user's application also will impact the size of whatever compressor tank is needed. When quick, concentrated bursts of air are needed, such as with a nail gun, a smaller tank is best. If the compressor will be used for sustained periods—with tools such as board sanders, grinders and impact wrenches—a larger tank will work best. Think of it as blowing out a candle compared to blowing out a birthday cake covered with candles. You have to fill up your lungs for the birthday cake; the candle you can do with a puff.

Be sure to offer hose diameters and lengths suitable for most clients' applications, as well. A ¼-in. diameter hose won't work very well if a 3/8-in. hose is needed to handle more tools or longer runs of hose.

Choosing compressors with durable features will contribute to a longer lasting machine, which leads to greater cost efficiency over time, resulting in more satisfied customers. It's a positive domino effect. Investing in quality up front will pay long-term rewards for both distributors and clients.

Some long-term durability features to look for include a cast-iron cylinder, a heat-dissipating head, an efficient cooling system and structural protection for critical components and fittings. Also look for a heavy-duty steel frame and powder-coat or electrostatically-applied paint to resist chipping and wear. Anti-vibration feet will help keep the noise down, and more importantly, keep the compressor from rattling itself apart.

In addition, examine compressor manufacturers before choosing a line. Ask questions. Are air compressors the primary or sole business of the manufacturer? Does the company make its own products or source them from a third party? How long has the company been in the air compressor business? Can the supplier answer all of your questions clearly and explain the subtleties that only an expert would know? What about the availability of technical help, parts and service, and the distribution network?

Overall, the most important factor is analyzing your end users' most typical application usage. Every job application has its own requirements and therefore its own set of questions and necessities. Do you deal primarily with framing contractors? Professional painters? Machine shop owners? Consider the end users' needs, and the most appropriate equipment option will be clear.

Remember, what you're ultimately distributing is not an air compressor. It's a solution to a client's problem. Analyzing all the factors involved will ensure that the client receives a complete solution rather than a temporary fix.