Bumping the thread because people might find this helpful.
I bought my Epson 8700UB less than 3 years ago and got my first "dust blob" a couple weeks ago. Despite running a living room air-filter, a giant green blur (about 6 inches across on my 110" screen) appeared right near the center. Totally visible on pure-black frames, ruining every movie I tried to watch by breaking immersion. Some people said to wait for multiple blobs before attempting surgery, but it was unacceptable to have my immersion broken consistently.
I dismantled the projector and used a vacuum cleaner in all the crevices but couldn't get close enough to the internal optics. Vacuuming had no effect.
About to give up and look into professional servicing, I tried one last thing: My electric leaf blower.
Brought the leaf blower into the living room. Inserted earplugs. Turned the leaf blower to "low" and, with my Epson 8700UB fully assembled (and turned off), I blew into the intake filter, both lens adjustment dials, the out-vent, and the lens. I turned on the projector, set it to a pure black image, and to my horror I'd spawned a second dust blob, even closer to the center! I'd made things worse!
In frustration, I left the projector on, cranked up the leaf blower to "medium" and fired directly into the intake filter. The second dust blob vanished, leaving only the initial blob! Progress! I walked around the projector, blowing into every orifice, including the out-vent (which I'd forgotten was running at the time), but nothing could affect the initial blob
Finally, with the blower on "maximum", I turned off the projector, took off the intake vent cover and vigorously blew directly onto the filter and the open video input ports for about 30 seconds. I finished by blowing, once again, into every orifice.
Turned on the projector, waited for the "EPSON" logo to come into focus, studying the area of the blob intently because I know the dust blob usually only becomes clear during the end of the warm-up phase. It was gone! With this relatively easy, low-tech solution, the image is now pure, crisp black throughout and I saved myself expense of sending it in for repair, or possibly cutting a control cable by taking off the upper control board. Thought I'd share so that other people know there is hope,
and to give people the comfort of knowing that someone has braved using a dangerously powerful device on the Epson without damage.