How do you know if it is working (fresh air)...

Question

I bought 2 of these Fresh air units on Ebay, they are different, one has " away mode" and one has "sanitize" in the right hand bottom corner.  Neither came with a manual. I do not know if they will give indication of when to clean or not, I am not sure how to operate the "ozone" mode..so I am afraid to use either one of them. Anyone know how to know what model it is and how to get a product manual for the correct model?