When you take the cover off, remove the scrubbers (plus the cell and solenoid trays), there's two 15cm/6' holes with the lungs underneath. You can reach in and clean the lungs with a cloth. With the unit standing upright (praise be for stands), there's plenty of air circulation to dry things out.On the inside of the lungs?
When washing the unit, you lay it down flat and fill the inhale lung with chemgene/whatever and the liquid balances over to the exhale lung via the loop. When done, remove the loop and it pours out, then hose out the sterilised water. Tip the water out of the top, then stand up and wipe down with the yellow cloth. Sorted.
(Assuming that some people aren't familiar with the Revo - the above is one of its strong points).