I do not have experience with that specific particle sensor, but I have interfaced and used a similar sensor from Honeywell.
To answer your question, "how can I verify the measured data is it correct or not? " You simply can not do that easily. To validate a sensor, you need to provide standards. In this case, the standards would be atmospheres with known concentrations of particles of a particular size, e.g., 2.5um. Moreover, to truly test how well the unit is calibrated, you would need to present atmospheres of different concentrations and of different particle sizes.
It is just not easy for you to do that. Nor is it easy for the manufactures to do that and I strongly suspect that they use something like the Chinese cigarette smoke model or similar...there are a few.
A second and more common way of "validating" a sensor is to compare it to a sensor that has some kind of better or "accepted as better" calibration. In other words, compare values received by your sensor with those obtained from a "better" sensor. Such equipment is referenced in the scientific literature and you find them at laboratories at places like the EPA and so on.
As a gross test to determine whether the unit is working in some general way, simply light a match, blow it out and let the smoke trail hit the inlet valve. They probably do some internal average of values (let's say every 10 sec or something), but you should see a dramatic rise in the concentration values accross the range of particle sizes.
Before going further, I would ask you whether you have read and understand the **broken link removed** for the sensor? How are you interfacing the unint - UART or I2C? What board are you using? Are you using canned drivers (and/or programs) from a
Sparkfun unit and not really understanding what they are doing? I am not trying to insult you or be presumptuous, I am just trying to understand your level of experience and knowledge about the area.
Hope it helps.