Integra System: One-of-a-kind air/fuel shut-off device offers double protection; Maintenance free - no filter to clean, standard replacement parts. Environmentally Friendly Burner: Low NOx design for low nitrous oxide emissions, self-cleaning, EverKleen patented system fights sediment build-up, reduces fuel costs, provides more hot water. Easy to Light: No matches required. Energy efficient: more hot water at low operating cost. Longer Life: Patented magnesium anode rod design incorporates a special resistor that protects the tank from rust. High Altitude Compliant: All models are certified for applications up to 6,000 feet above sea level. Some models are certified up to 10,200 feet above sea level. Check factory for listing. Plus: Temperature and pressure relief valve is included, specially formulated glass lining prevents corrosion and extends the life of the tank. Meets or exceeds National Appliance Energy Conservation Act (NAECA) requirements.