I responded to a commercial heating issue in a warehouse. The Lennox furnace was experiencing ignition failure, leaving the building without heat. Upon inspection, I found a cracked heat exchanger and faulty igniter. I replaced the heat exchanger with a new one from Lennox and installed a new igniter. I also cleaned the burner assembly and tested the unit for carbon monoxide leakage. After completing repairs, I conducted a full system test to verify proper operation. The heating system was restored to optimal performance, providing efficient and safe heat throughout the warehouse space.