Dear mekky,
Can try this older post as a starter (20008) -
http://www.ifsqn.com...dpost__p__22352Also see the surrounding posts in same thread, eg Nos #18, #25
You will observe that significant difference of opinion exist. Local regulations may apply also.
If you try searching for "swab" you will pick up several later posts / data also, eg this one -
http://www.ifsqn.com...dpost__p__34195(most data are for relatively "clean' environments perhaps not quite comparable to yr request)
I recall one arbitrary rule-of-thumb for an
operational level that the TPC must be less than one tenth of the value of the product on it.

Obviously just cleaned/sanitised surfaces will differ.
Rgds / Charles.C
PS added - this one, although 2008 origin, is quite interesting also (and still active!)-
http://www.ifsqn.com...dpost__p__23287