If you want to keep them in your apartment I would suggest you keep them empty.
Hummmmm, Your profile doesn't fit your SCUBA knowledge.

Gary D.
Welcome to ScubaBoard, the world's largest scuba diving community. Registration is not required to read the forums, but we encourage you to join. Joining has its benefits and enables you to participate in the discussions.
Benefits of registering include
If you want to keep them in your apartment I would suggest you keep them empty.
From a property managers point of view (NOT AN ATTORNEY and I do not play one on TV). Consult an attorney for legal advice. IMHO Most standard leases in my state (CA) have a HAZMAT clause. In my mind I am thinking of things like chemicals, solvents, oils, explosives etc not SCUBA equipment being covered under this clause (but I can see where they could be included). Of course as a SCUBA diver, I would not think of this as HAZMAT because I am familiar with the equipment. Best to discuss with the manager before you sign the lease and ask them to define what they consider covered by the HAZMAT clause. I would also mention that you scuba dive and would be storing your air (stress AIR as everyone thinks they are oxygen) tanks there. You might also tell him/her that you are a trained oxygen provider (you are aren't you?) and have emergency oxygen in case a medical emergency should arise in the building.