The House Detective: by Barry Stone, Certified Home Inspector
Dear Barry:Ever since we installed wood flooring, we notice little white granules on the floor every morning. We previously had white carpet, so we never noticed this before. We suspect that this is coming from the forced air registers in the ceiling, but we had the furnace checked by a heating contractor. He said the system was OK. We’re tired of vacuuming every day and are worried that this might be a health risk. What do you recommend? Joan
Dear Joan: If the white granules are coming from the heating system, this could be the symptom of a serious defect in your furnace. Step one is to confirm whether the forced air heating system is the source of the white granules. To do this, you should place filters inside the air registers where the problem is occurring. If white particles show up on the filters, the furnace is the source of the problem. If your heating contractor failed to identify this, you should contact another heating contractor and should discontinue use of the system until you have a reliable evaluation.
The combustion exhaust in a furnace is acidic. If this makes contact with galvanized steel, the acid will react with the zinc in the galvanizing, and this can produce a white powdery residue, as is commonly seen on the terminals of a car battery. If this substance is getting into the circulating air system, there could be a crack or hole in the heat exchanger, and that would be hazardous. Again, you should have this system thoroughly evaluated by a qualified HVAC contractor. You can also have the white particles analyzed by an environmental laboratory to determine their chemical composition.