First of all, is a CMOS chip in this camera, not CCD. I mention this as the coatings and or filters on the sensor may be unique, thus if you wet clean make sure the solution you use is compatible.
I don't feel you can expect to ever have a built in "dust removal" system get all of the dust, albeit the one in the Canon 5D MKII did a very good job. If you have a hair, then you should be able to blow it off with a rocket blower. If this won't get it off, then you would need to consider a wet cleaning.
There are many companies/methods to use, some to consider are Visible Dust, or Eclispe and a pec pad. You need to check with each company to make sure which solution they recommend to be used on your sensor and the swap type. Most of these companies have a list you can read over.
The chip in your camera is a micro 4/3's so it's smaller than APS-C, make sure to get a swab for that sized sensor. EM1 is mirrorless, so when you take off the lens, you will see the exposed sensor and can try the blow off method first, then try the swab.
If you don't feel comfortable with a wet cleaning, then you can always send it off. to Oly. But this is a pretty standard process now.
Paul