This is the nice thing about the old Kodak backs and the Mamiya ZD backs. The IR filters are clip-on, clip-off; so you can easily clean both the filter and the sensor cover glass. Or replace the IR filter with an anti-moire version, for certain shoots. Or shoot with no filter and a massive IR response, if you want!
I wish PhaseOne & Leaf would use this clip-on, clip-off filter design. It is
one of the things that MFDBs _can_ do that DSLRs can't - it is
a selling point. Kodak and Mamiya realized and exploited this; why can't PhaseOne et al.?