With dozens of highly rated air compressors to choose from, it was a challenge to select the top performers for our hands-on tests. We considered brand names to an extent—after all, manufacturers such as Ca. While a reciprocating air compressor is quiet, a rotary screw air compressor is more silent. This air compressor has two separate helical screws working in unison to get the job done. Note that the two screws do not come in contact with each other, making them quieter.
[pdf] It should turn around smoothly, without any 'hickups' (be sure to completely shut down the air compressor!). Check the isolation of the motor windings. Should be in the mage-ohms (you need an isolation tester / high voltage ohm meter for this). Check the voltage when the compressor is running.
[pdf] Compressor air screw VSDs usually have noise levels ranging from 60 dB to 85 dB, depending on the factors mentioned above. When selecting a compressor, it's important to consider the acceptable noise level for your specific application.
[pdf] 
