Vlad (and any one else having these cartridges)--I would [color=#FF0000][b]highly[/b][/color] recommend keeping them in an airtight zip-lock bag. The poison in the cartridges is Potassium Cyanide. It is a dark gray powder that volatilizes to an extremely poisonous gas. This gas is heaver than air and will settle to the bottom of your storage cabinet or to the floor where it is especially dangerous to pets. The gas has the odor of almonds. If you detect that odor, ventilate the area well. I have worked with Potassium Cyanide for many years, using it as an insect killing bottle agent (I used to be an Entomologist). It does not take much to kill you. Once in the lungs, it is VERY hard to expel it and it is readily taken up by the blood. I always followed the rule that more than 3 deep breaths of it and you will be dead before you can reach medical aid.
In my case, the cartridges in my box have become corroded with grayish white crystals of cyanide because the black seal (I think it is pitch) has lost it's seal. Even though I keep the box in a zip-lock bag, I take it outside on a warm day (cold retards the forming of the gas) and open it to the air for at least an hour every year to vent any gas.