I asked Founding Director of the Space for Art Foundation and former astronaut Nicole Stott about this, she kindly gave me permission to quote her.
That is meant to be a protective kind of shield for the rack - to keep
people from hitting the rack or using the hand rails for translation
(so the rack stays as "still" as possible for the micro-g ...
For the US space program, it started in Skylab.
Vacuuming of the Orbital Workshop mixing chamber screen, the waste
management compartment screen, and other environmental control system
screens was performed on an as-needed basis, usually about every other
day. Screens with large mesh did not require vacuuming since most of
the debris passed through them. ...