No need to fear preparing ackee that you obtained from a can.
The problem is fresh ackee in the pod. IF the pod is FORCED open to remove the ackee, then the ackee is poisonous. If the pod stays on the tree and OPENS NATURALLY, then there is no need to fear eating the ackee. All the poisonous fumes escape naturally and the ackee is no problem to eat. Ackee is also eaten raw and the person eating it doesn't suffer from any ill effects.