We live in Louisiana in an apartment and have black mold coming out of our vents?

The first thing you need to determine is whether your 'black mold' is of the type which is dangerous. Understand that common mildew is also black, and is of no harm. You will need someone to get a sample of the mold involved from inside the vent and have it analyzed for type.

This will be at YOUR expense. If the mold is not found to be the harmful type, you eat the cost of the mold test. If it is, indeed, harmful black mold, then the landlord must remediate, and you can get the cost of the test back from him as well.

The landlord is responsible regardless of whether or not it's the " dangerous black mold." FYI, for some people, all molds are dangerous and if you and your family are getting sick it obviously is "dangerous." It is his responsibility to come in and look at that and pay for any needed repairs or testing. It is far more cheaper for him to do that than risk the chance of you and your family becoming seriously ill and suing him for all he's worth.