Unlike a boiler, your furnace does not need water to operate, and there are no leaks in the vicinity.
So why is it rusty? A rusting furnace may seem odd, but it may indicate something more serious.
While conducting maintenance and repairs, a reputable, experienced heating repair business would check for this. It is unlikely that surface rust caused by nearby moisture is a major concern, but it may indicate serious interior problems. If you see rust on your furnace, do not use it until an expert HVAC technician verifies it is safe. Rust on the heat exchanger, an internal system component, often goes unnoticed by homeowners. Maintaining your furnace is therefore crucial every year. When rust spots appear on the heat exchanger, it indicates that it may fracture. A corroded or broken heat exchanger should be replaced or repaired promptly to prevent hazardous, possibly lethal combustion gases such as carbon monoxide from entering your home. If the exhaust and drain lines get clogged, the minute fluid produced during gas combustion is not adequately removed, increasing the risk of moisture exposure and corrosion. Corrosion will occur due to prolonged exposure to combustion, making older systems more likely to exhibit rust on the heat exchanger. Buying a new furnace is a better investment than repairing an old one. In contrast, modern Energy Star systems achieve up to 97 percent efficiency, guaranteeing a quick return on investment and a more pleasant home environment. If you notice rust on the furnace’s exterior, this indicates that it’s time to replace it. The corrosion and rust in your furnace can leak gases into your house if the pollution creates a large enough leak.