I could use, and would be grateful for, a good narrative for no firewall between units in the attic of a duplex. Thanks in advance!
Photos please Ruddel. I will try but picture would create the backdrop.
Upon entering the attic space, my observations showed that no fire separation has been provided to separate the two units.
Two-family dwellings, in most jurisdictions, are typically separated from each other by a wall and/or floor assemblies having not less than 1-hour fire-resistance rating.
They usually extend to the underside of the roof sheathing or exterior wall assemblies.
Checking with the local Jurisdiction could confirm this requirement.
Hope this helps. 
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Sure would be nice to see a picture. Is it possible the the floors have 5/8" type x drywall and there is a draft stop vertically in attic?
Some jurisdictions (many) allow 5/8" drywall at ceiling in place of attic separation.
5/8" drywall…
1/2" Gypsum type X…
two layers of 1/2" drywall…
…around these parts anyway.
In as much as the garage probably already has 1/2" drywall in the ceiling and on the house wall, adding another 1/2" might prove the less expensive method.
Then there’s the issue of exposed wood framing around the hatch!
Or a** wooden pull-down ladder…**
You had many to help you. Here is some technical.
http://sdinspections.com/understanding-firewalls
Thanks all!
Good luck.