My free air compressor plugs into my cars 12 volt power outlet. When switched on, it will discharge compressed air at up to 125 PSI.
Of course the flow rate of air from this air compressor is very low. So low that it might take what seems like forever to fill up a tire or air mattress. But...it is a portable air compressor, for sure!
So, when looking for portable-compressors, you have to first decide what are the applications you need compressed air for?
An air driven jack-hammer will require the output from a towed 175 CFM portable compressor. A small blow off gun will only need a very small air compressor. How do you choose?
If you are not sure about your air tool consumption here is a guide to air tool compressed air demand.
The little compressor shown below is just that, a little air compressor.
Yet, if we had a low tire and were stuck somewhere in the wilderness, and we could plug this air compressor into the vehicle power supply, we could sit in the relative comfort of the vehicle while it slowly...oh yes, oh so slowly, brought the tire up to pressure.
That is, assuming it works when you need it! I tried to use one similar to this the other day, and the darn thing would not cycle, and burnt the fuse. A good lesson. You sure want to test your air compressor periodically. Do not assume that just because you have it with you for years in the trunk of the car, that it will work when you need it.
You do need to be a bit careful when using these little air compressors, too. Some of these low flow, compact air compressors can put out 250 PSI, and with enough time might blow the tire, or an air mattress or a beach ball to smithereens!
While the air compressor shown in the first photo will need a special power receptacle to plug it into the car, the next one is a portable air compressor that can be carried from place to place on the job site, and plugged into a standard 120 volt outlet wherever compressed air is needed.
What portable compressor will you choose if you are working on a job site nowhere near electrical power? Gas powered? Diesel powered? Before selecting a portable compressor, give some thought to how you will get power to run it.
If the portable air compressor you choose does not come equipped with an in-line compressed air filter you will want to add one if your air use is fairly constant.
The majority of portable air compressors are factory equipped with a compressed air regulator. Air regulators offer benefits such as reduced air/energy use and reduced air equipment wear. You do not drive your car with the foot to the floor on the gas pedal all the time, why operate your air tools with the air pressure equivalent? Run your tools at the lowest working air pressure for longer tool life.
An air regulator, set 10-15 PSI below the compressors low pressure set point (also known as cut in pressure point) will help ensure that your air-using application will see a steady stream of compressed air at a non-varying pressure. As the pressure in the receiver peaks and wanes due to compressed air use, with the regulator set below the compressors lowest pressure setting, your application should never experience a change in that constant, lower pressure flow.
That is, unless the various air tool demand for compressed air outstrips the ability of the compressor to keep up. In this case, the pressure coming from the receiver will continue to decay down past the regulator setting, and it will keep dropping as long as more compressed air is being used by your air tool than your compressor can generate.
Some air tool oilers are installed in the air line just before the air tool. A high-use, high-air-demand air tool may benefit from one.
On the other hand, if your application is, for example, air brushing, then you do not want oil spraying out with the paint, and no lubricator would be installed in an air line to a paint spray gun.More information about portable air compressors continues here.