When I bought my compressor I tested the air upon first use. I let the compressor build pressure to 300 bar then bleed the air several times to insure I was testing air compressed by the compressor. Test conditions were @ 78 degrees in my air conditioned house in Arizona, when I tested I had the dew point in my house but I can't find the number. But it was a dry day. This is for comparison, my tank was about 5 years old and had only been filled by AOA air in my tank was less than 20 PPMV all measurements were air going into the analyzer @ 3000 psi. Results: New Omega Turbo Charger Compressor @ 3000 psi was putting out 119.3 PPMV. Thats Pretty wet so I didn't put it in my tank or guns. I bought a filter from AOA and duplicated the test. With the inline filter the air going into my bottle the air was now was lower than my 24 PPMV goal. That was a couple years ago and I haven't done any further testing. So I would recommend a filter.