Reprinted from Rabbi Felder at SSCM

One may not eat Kosher L'Pesach food on a table with someone who is eating
chometz (ie at work or in a park). However, being that the chometz is in the
goy’s possession, one does not require a äöéçî for the chometz.
Likewise, if a goy enters one’s home on Pesach (ie cleaning lady or a
plumber), if possible, it is preferable to have he/she refrain from bringing
chometz inside.
If the goy does bring chometz inside, it does not require a äöéçî in front of the
chometz, as the goy is present with his/her chometz. When he/she leave,
one must insure that the goy cleans up and remove all his/her chometz.
If the goy does not remove his/her chometz, one should have in mind not to
aquire the chometz. Additionally, one should clean up and remove the
chometz indirectly and without touching the chometz (ie, with a
broom and dustpan).