Using a cartridge to contain the killing agent was an original BioQuip concept in 1959. A porous hard plaster cartridge securely encloses the killing agent yet permits fumes to seep through into the jar. The cartridge screws into an inner metal lid riveted to the widemouth jar lid, and does not crumble or break with normal use or in humid conditions.
Clear glass jars with plastic lids have red skull and crossbones labels for safety. They are shipped without being charged to allow shipment through the mails. Cyanide crystals (not sold by BioQuip) or cotton saturated with #1185A ethyl acetate may be used as killing agents. Use of ammonium carbonate with these jars is not recommended; it softens the cartridges.
Replacement cartridges are available.