I don't want to teach my grandmother to suck eggs, but I presume you all know you should take the filter out of the back of your concentrator, put your spare one in and wash the one you took out then it is ready for the change the following week. I was amazed, where I had the windows open it had dandelion seeds in it. The service engineer gave me my spare when he came to do the six monthly service. If you don't have a spare I should ring your oxygen .supplier. Keep smiling
Carole x