In any substance that is frequently infested or even sometimes infested, checking a sampling of the item―even checking most of it―is not good enough.
We have mentioned that, even a substance that is sometimes infested (mee-oot hamasui)―must be checked. Consequently, one could check, let us say, ninety per cent of the item and not find a bug. Still, the other ten per cent can be infested. So, the partial check―even if it is actually a check of ninety per cent of the item―is not enough23.
If, however, the item is normally not infested, or if it is rarely infested, checking a sample does help(in a case in which one fears that in this instance there might be infestation)24.
By the same token, if a substance is normally infested, but is now grown with special precautions to prevent infestation, checking a sampling of the item does help―since the item is considered to be like an item that is not normally infested.