I have a customer that has a First Co. air handler with a hydronic coil heated with a Polaris water heater. They had the system installed 14 years ago, and just called me with the DSS issue. When they fired up the heat they smelled it. The wife says it's unbearable to smell. I understand the heat pump coils heating up and smelling, but what about an ac only coil? Or maybe it's the heating coil? I don't think the ac coil gets hot enough to raise the bacteria, so does anyone think the heating coil could have gotten funky? Now, what to do about it?