FYI, there is confusion about the Dawn soap. However, I contacted both Resmed and Respironics and all of their masks are safe to use with Dawn dishwashing detergent.
To JJJ: some manufacturers use plastics that were damaged by using Dawn dishwashing detergent. In addition, in some cases of soaking, the mask can absorb the odor of whatever you use to wash your mask parts. My brother has a Fisher&Pakel mask and hated the smell of Dawn, so when I do soaking, I use water and vinegar. He prefers the odor of pickles. I never get any odor from my masks.
I have no idea why they told me this, I am just repeating what they said.
I would guess the milder the soap the longer the mask seal might last. Just a guess.
They told me to clean mask and tubing weekly. Change water in tank daily and to only use distilled water in tank.
And that was about all the info they gave me, everything I have learned has been from the good people on this forum.