sometimes you need more than one object to produce smoke but hups? what’s that? Just one object produces smoke.
The solution and the reason for this problem are simple:both objects are in the same flow group
What’s flow group?
You can create for an object a group via:
pressing on the cube in the right side bar (where can preferences of objects)
then scroll down to groups and press on the + sign to create a new one
And now you have a group. To asign a smoke domain to a group go to the smoke menu and click into the field flow group, then assign the group with the right smoke producing object.