You want to check with your local Fire Marshall or Building Department.
1994 Fire Stops
Fire blocking is required in all stud walls at ceilings and floor levels.
Fire stops must be a minimum of 2X nominal thickness, two thicknesses of 1-inch nominal lumber with broken lap joints, 23/32 plywood with joints backed with 23/32 plywood, one thickness of 3/4-inch Type 2-hour particleboard with joints backed by 3/4-inch Type 2-M particleboard, gypsum board, mineral wool, or other non-combustible material securely fastened in place. Single Family Residential Construction Guide - Wall Framing
2009 R302.11 Fireblocking. In combustible construction, fireblocking shall be provided to cut off all concealed draft openings (both vertical and horizontal) and to form an effective fire barrier between stories, and between a top story and the roof space.
Chapter 3 - Building Planning