Instruct: Classify the given Amazon review into positive or negative sentiment.
Query: DID THE JOB

WE HAD A SERIOUS DUST BUILDUP COMING FROM SOMEWHERE. WE HAD OUR DUCTS PROFESSIONALLY CLEANED. WE REPEATEDLY INSTALLED NEW FILTERS ON OUR HEATING/COOLING SYSTEM HOPING TO FIX THE PROBLEM. ALL THIS GAVE US NO RELIEF AND PROVED UNSATISFACTORY. I CHECKED AIR PURIFIERS ON AMAZON. JUST CONSIDERED THE HIGHEST RATED DEVICES.WITH MY FINGERS CROSSED I BOUGHT THIS A MONTH AGO. IT HAS BEEN ON 24/7 SINCE THEN AND WE HAVE DEFINITELY NOTICED A BIG DIFFERENCE IN THE CLEANLINESS OF THE AIR. YESTERDAY, A LONG TIME FRIEND STOPPED BY AND ASKED IF WE HAD A NEW AIR FRESHNER IN THE HOUSE!! THIS PURCHASE HAS BEEN A WINNER AN IS HIGHLY RECOMMENDED.