In a cleanroom, cleaning floors and walls is like cleaning other surfaces, only more so – larger surface areas and corresponding larger wiping cloths. Let’s start with floors.
The same principles apply to wiping floors as described previously in Particles on Surfaces Part 4 – use linear wiping strokes and wipe from clean to dirty. To achieve linear wiping strokes, flat surface mops using pre-wetted mop covers (“booties”) are most convenient. The mop covers are changed when they become visibly dirty or after a prescribed surface area has been cleaned (perhaps 100 m2 but this depends on the cleaning protocol for the particular cleanroom). Mopping from clean to dirty is easy to figure out. The dirtiest area of the cleanroom is the entry door adjacent to the gowning area, since it gets the most traffic. The cleanest area is either a very lightly trafficked zone, or the area furthest from the door. So mop from those areas toward the door. The entry door area should be cleaned at least daily.
Walls are generally cleaned less frequently than floors since they do not encounter contact transfer of contamination like floors do. (If your people are constantly bumping into walls, you may have another problem.) The same flat surface mops work well here also. A little thought reveals that the cleanest area of the walls is at the ceiling at the output of the HEPA filters. The dirtiest area is the wall adjacent to the floor. Two wiping patterns are available. Vertical wiping is the most convenient and ergonomically satisfying, since gravity assists the downward wiping motion. Horizontal wiping works well too and has the advantage that mop covers may need to be changed less frequently than for vertical wiping, since it is expected that the top two thirds of the wall surface is likely very clean and new mop covers should not be required for cleaning those areas. Obviously, soiled mop covers must be changed immediately.
Next up: How do we know that the wiped or mopped surfaces are clean?
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