Your UV flame scanner might be detecting a spark—not an actual flame. That's a safety problem worth understanding before it becomes a real one. Jude breaks down the two primary flame scanner types—UV and infrared—covering which fuels each handles best, and demonstrates live on a burner how a UV scanner can falsely detect an ignition spark as a flame signal. He then shows the fix: ignition transformers specifically rated to be invisible to UV scanners. A flame scanner that reads a spark as a flame can mask a failed ignition and allow unsafe burner operation. Understanding this distinction is critical for anyone maintaining or troubleshooting gas-fired boilers. Safety notice: Always consult experts for complex repairs. Weekly Boiler Tips are compiled by the knowledgeable and remarkably prolific content creators at WARE, a family owned, third-generation, 69-year-old commercial and industrial boiler rental and service firm based in Louisville KY. You can learn all about this and more at WARE's Boiler University.