[Shortman]

Once opened and exposed to air, the shelf life of Killem is about one year. The active ingredient in this biocide is "Sodium-dithiocarbamate" which is a salt and will tend to crystalize, over a period of time, once exposed to airborne contaminants. The shelf life could last longer if kept tightly sealed and in a cool, dry environment. The product still can be used past one year, albeit it will not be as effective as fresh product.