You may need to be more specific regarding any context for (a).
For (b) I assume you mean food contact surfaces rather than the atmospheric environment.
I assume you mean pathogens and not, for example APC counts. Regardless, in practice the former are often combined with the latter.
No particular pathogens ?
I enclose 4 documents on environmental monitoring (env4 orig.attached by esquef).
env1 - kraft - Environmental Monitoring, 2004.pdf 928.44KB
env2 - RTE, GMP, SOP, ENVIRONMENTAL SAMPLING-TESTING,1999.pdf 219.58KB
env3 - Guide to Environmental micro.testing, Microgen.pdf 214.23KB
env4 - environmental monitoring program, 2013.pdf 3.7MB
There are also numerous documents here specifically for individual environmental pathogens, notably Salmonella / L.monocytogenes, eg -
Rgds / Charles.C
PS - I abbreviated yr thread title to try and get it all in. Feel free to adjust again as preferred.