I am corresponding with a newbie and sent her this message as she was not given white filters with her machine. Since changing filters is important, I thought it was a good idea to post the information here
I also have a Respironics machine and they all have the same filter setup. You need to use a white filter and a black filter at the same time. As you said, the black filter is the washable one and should be washed once a week. Insurance allows for 1 black filter every 6 months.
The white filter is a disposable one and needs to be checked each week for dirt. The white filter usually lasts about a month before it get dirty and needs to be thrown away. The white filter with the plastic side goes against the machine and the black filter goes against the soft side. When the cover for the filters is put back on, make sure that the open slot faces down.
On page 1 of the Remstar Patient's Manual where it shows a picture of all of the components, one of the items listed is the white ultra-fine filter. Insist that your DME gives you two. They should have come with the machine. If you have any trouble, show them the Patient's Manual.
After you receive your machine, you are responsible for ordering any supplies you need which you can do from your DME or you can do it online from a supplier like cpap.man. If you have insurance, you can order from Bill My Insurance.
Do you know which Respironics machine you have? The name of the machine is on top of the machine in large letters. On the bottom of the machine is a label with the name, model no, and serial no. If you lift it up, be sure you disconnect the humidifier so you do not get water in your machine. Do you have a heated humidifier?