Have you recently replaced the mask?
If not, it's time. They need to be replaced about every 3 months.
If you have, here's a couple of things to try:
1. Start from scratch. That is loosen all the straps, wash your face and the cushion to make sure nothing is oily. Then put the mask on and tighten just enough to keep it from falling off your face while adjusting. It WILL leak at this point. Now, hook up your machine, and on the inspiration phase (when the air is coming in), gently tighten the lower straps only the bare amount necessary to stop it from leaking around the bottom. On another inspiration phase, do the same with the top straps and then the forehead dial. The goal is to have it as LOOSE as possible so that the cushion is fully inflated.
2. While the machine is on, try pulling the mask gently away from your face and then reseating it on your face during an inhalation phase to make sure the cushions are inflated and not creased anywhere.
3. If you are still having leaks after the above, try putting a thin layer of Lanisoh cream or KY jelly on the edge of the cushion to help it seal to your face OR make a thin gasket out of Mack's silicone ear plug "putty" to make the seal. If it's only leaking in one area (e.g. the bridge of your nose), you can use a rope of the silicone putty to try to seal that leak.
If you have a brand new mask and you'v always had leaks with the Quattro, you're not alone. It seems to have a reputation for lots of leaks (and that's been my experience, too). Maybe you need a different mask?
Phillips Respironics System One Auto A-flex and Humidifier
Encore Viewer 2.0 Software