Its just fibre filters, and charcoal. Thats it. There are systems before it that ensure it only sees vapours, but there is a drain/air inlet on the bottom, plus the line to the tank on the top, and the vac line on top. When the car sees you're cruising in gear, it purges the charcoal canister w/ the purge solenoid, allowing the vacuum of the motor to suck all the vapours out, with the drain being an air inlet, and the material and charcoal acting as a filter.
When its not being purged, positive pressure in tank is regulated by systems before the canister, and the excess vapours are sent there. The drain then acts as an overflow, and the charcoal holds onto the vapours.
Charcoal is a rather safe substance, being mainly carbon. It burns awesome as a result, and gives off primarily CO2.
Yay. I'm edumacated in one more thing
