They will however act if for example a sample of chocolate has 90 or more insect fragments per 100 grams (approx 3 1/2 ounces) or if 6 100gram samples contain an average of 60 or more insect fragments per 100grams.
Alternatively if any one 100gram sample of chocolate has 3 or more rodent hairs, or 6 samples have an average of 1 or more rodent hairs.
Infestation below those levels - caveat emptor!
Its a free market after all.
Chris Burford
London