I wrote an earlier review that I regret I really didn't get into what this unit actually does. This is my third air filter from germ guardian / lasko. The other two or smaller units their air filters had a charcoal wrap on the outside of them. Where this one the charcoal is embedded into the filter and wrapped in a fine mesh, this makes it a lot easier to clean with the charcoal embedded inches of filter you don't have to pull it off and clean the filter as you would in the smaller ones you just vacuum the outside of this filter. The sensor on this machine is very good also on high allergen days I have noticed that the sensor reading on the front display does go up quite a bit also if we are cooking it will go up, it removes the allergens and odors very well I have chronic allergies so therefore even when the meter is reading low I still have to occasionally turn it up on the fan speed to two to help myself. I would highly recommend this unit that's a good company I would say I would get this one versus a small ones just due to the fact the charcoal is actually embedded into the filter and a mix and on the smaller units you have to take the wrap off on the outside and as you do that the charcoal does come apart and it goes into the filter so it's kind of defeating the purpose a little bit where this one is much easier this one does cost a bit more but overall it's easier to maintain.