I have heard that one should not step on crumbs. How small of a crumb though should one be concerned with? Also, is the concern specifically with bread crumbs or any food particles / crumbs.
The poskim bring that one should sweep the area that crumbs fell, in order that they should not get stepped on. If the crumbs are microscopic we don’t have to worry about them, they same way we don’t have to worry about anything that is too small to be able to see.
Although we should not step on any food, this surely applies to bread cake cookies etc.
M:B. 180-10, Ben Ish Chai 2 Pinchos 12, PIskei Teshuvos 180-4, 171-2