[creer]

That's really not true. In both ways, too. It's not realistic.

In the specific case of gluten-free vs normal flour, you might have a clean, safe kitchen but flour flies everywhere and it doesn't take much. The solution for a gluten-free kitchen is to only use gluten free products. I know of a restaurant that offers both gluten free and plain pizza crust and people who need to should know what that means: they try but it's not.

It's also not realistic as to "safely eating off surfaces". That's the goal and that's what test kits test for - but that's the point: the test kits are there because it's hard to achieve (and excess will result in contamination from cleaning products.)