I don't know much about this. I use a humidifier when I feel like filling it up and don't when I don't. I loved it at first but its not that big deal. I don't have sinus infection issues but I do have alergies and I have found that they improve when I use the machine at night, and even more when I use a humidifier. Tell your peeps to clean the heck out of their machine, filter bong (the humidifier resivoir) and hose and mask. Tell them to get ahold of secondwindcpap.com that place sells refurbished cpaps and they do the service on them and they clean them. I don't know if they do it as a standalone service, but it couldn't hurt to ask. I haven't really heard much about this but I haven't looked for it either. My suspicion is that its a cleaning issue if its related to the machine. I wonder if we can get a sticky put on this topic so that it stays at the top for new members? Does anyone know how to do that?