The Ari z”l writes that one who is careful not to eat even a tiny bit of chometz on Pesach is guaranteed not to sin the entire year. (BaH1)
Mid’oraysa, chometz on Pesach is like any other issur which would become bottul 1:60. However the Chachomim decreed that even a tiny bit of chometz that falls into Pesach food will make the entire mixture forbidden even to benefit from. The mixture must be burnt. (ShA1 — MB1)
There are ways to avoid a monetary loss if the loss will be substantial, or if there are many other mitigating factors. (MB2,3)
Pots that have been used for chometz are allowed to be kept for after Pesach; just wash them clean before putting them away. (Rama1 — MB4)
The above chumra applies only when the mixture occurred from the onset of Yom Tov until after Shmini shel Pesach, when the issur of chometz becomes a chiyuv korais. If there is no issur korais, the Chachomim allow the chometz to become bottul according to regular rules of issur mixtures. This includes: (a) the mixture occurred before Yom Tov including after chatzos on erev Pesach; (b) the mixture was one of chometz nuksha; (c) the mixture was merely ta’am tifgam. (ShA2 — MB15)
Whenever you want to be machmir for a suspicion of a doubt of a bit of chometz, make sure you will not be wasting food. You can eat it if the food will not last until after Pesach. (MB54)
You may not eat on Pesach spicy food that was cut or chopped with a chometzdig knife, even if the knife was clean. If you know the knife was never used for hot chometz, then the food is permitted. (MB86)
Noodles are not chometz nukshe; they are chometz gomur. (ShA12)
Some people refrain from playing cards on the Pesach table because of the worry that maybe some bits of chometz nukshe from them will fall into the food. (Rama12)
