At 09:39hrs units were dispatched to the reported building fire in the 12000 block of the Southwest Freeway, the former Texas Instruments property. While responding Engine 21 (Wilson) advised of smoke showing and upon arrival reported smoke from multiple openings in a 1-story and 2-story building being demolished. With the building integrity questionable, and water supply limited, all companies assumed a cautious stance as the fire was located in an elevator mechanical room involving the mechanisms, pump and hydraulic fluid. With Engine 23 (Delmar) as Fire Attack, Engine 22 (Peters) as RIT, and Engine 21 (Wilson) as Back-Up the main seat of the fire was located and knocked down. Upon placement of water on the fire Ladder 31 began opening all available doors and Engine 41 rotated inside while Engine 21 checked for extension to Division 2. Due to unknown fire extension elsewhere and zero visibility throughout the vast portions of the building additional assistance was requested bringing Houston District 68, Engine 68, Engine 73 and Ladder 68 and Pearland Engine 5 to the scene. With the Incident Safety Officer advising of possible barrels involved Harris County Haz Mat 1 was also requested for air monitoring and product ID while Cascade 72 responded for supplied air operations. Following extensive company rotations overseen by Operations Section (Partida) and ventilation overseen by District 68 as Ventilation Group all companies returned to service approximately 4-hours later. During the incident one worker was injured and transported by coworkers prior to arrival of 1st arriving companies on scene. Additional companies on the fire ground included Battalion 21 (Therault) as ISO, Battalion 31 (Keefe) as Division Charlie, Ladder 2 and Tanker 22. The cause of the fire is under investigation by the Stafford Fire Marshal's Office.