Pwave Door Fresh Brain Unit. Designed to go near the entrance by the door in your bathroom facility. Each time the doors open and close, the Unique design allows the fragrance to be released. The battery in the Brain then indicates when 30 days are up and you then change the air fresheners. There is a lifetime guarantee on Brain battery. Light flashes on day 30. As well as an audible beep on day 34. To view our full range of Pwave products, click here. For any product advice on this Pwave Door Fresh Brain Unit please give us a call on 01621 828882 and our sales team will be happy to advise you.