Long shot question, but what body are you using with this? Could the dust becoming from the body--for example, if you have this on a tech camera you have been using for longer than the back, could you body be contaminated with small particles? The back might just be sucking up what is in the camera. Perhaps blowing out the body might help. Just a thought...
It could be, I recently switched to new XF body from another XF body. However, the new body tested clean at another facility.
Thank you very much for your replies on cleaning, it's been very helpful. With the help of my buddy Steve I think we are narrowing it down to environmental. A neighbor is doing construction, we live in a wooded area of Pasadena that is pretty dusty and last but not least this little scamp recently adopted us. Short of building a clean room I'm going to figure out how to scrub the air in the studio.
One last question, do you think the pixel size of the IQ4150 makes dust show up that we couldn't see before?