Dispatched for a no-heat concern and to provide a second opinion on the existing furnace. Upon arrival, the system was operating and producing heat. A complete and thorough inspection of the furnace, heat exchanger, and all safety components was performed. During the inspection, it was discovered that the rollout safety switch had failed and had been bypassed by a previous service company, which is a serious safety violation. Further inspection of the burner compartment and combustion chambers revealed conditions contributing to improper flame rollout. While diagnosing the system, elevated levels of carbon monoxide were detected in the supply air, most notably when the inducer motor shut down. This indicates unsafe combustion conditions and presents a potential health and safety risk to the occupants of the home. Due to the compromised safety controls, flame rollout condition, and carbon monoxide spike, the furnace was determined to be unsafe to operate. For homeowner safety, the ga