The Ghosting Investigator’s Checklist

A brand-new white pleated filter, right. A similar white pleated filter, left, after only two weeks of use in a house in which the air handler ran continuously and the owners burned a candle in a jar for two to three hours, three times a week.
  • The very first course of action when investigating a staining problem in a home is to identify what the stains look like and where they are occurring. Are the stains on any particular type of surface (for example, on plastics, on walls only, at carpet-to-wall junctions)? This helps to determine whether the problem is created by something going on in the house or by house construction details. Stains on wall and ceiling surfaces that are clearly geometric in pattern, may be caused by poor insulation. What color are the stains? Soot is generally black. Dirt and dust stains are gray, but if they are present long enough or in high enough concentrations, they can be near-black in color.
  • A lab analysis of the stain is a nice–but expensive–luxury. If your clients can afford it–great; it beats guessing what the source of the stain is. If they can’t, detective work is in order. Look for signs of occupant life-style and possible soot sources. Candles (look at the length of the wick–the longer the wick, the more soot it produces); pilot lights on combustion appliances (especially fireplaces). Make sure to examine the size and color of the pilot light. Excessively long or yellow pilots are possible sources of soot. Ask your client lots of questions about how they live. Maybe they burn a lot of candles, but only on holidays. You may not see any because they’re packed away. Are there smokers in the house? How often do they use the fireplace and what type of wood do they burn (soft wood does not burn as cleanly as hard wood)? Examine the vacuum cleaner for possible contributions. If necessary, run it in a totally dark room, lit with a high intensity lamp. If the vacuum is spewing dust, it will be clearly visible.
  • Don’t neglect possible outside sources. Nearby high traffic areas, industrial settings, and construction sites are all possible sources for dirty pollutants.
  • Conduct a thorough diagnostics test of the house. This includes a blower door test of house tightness and series leakage tests of attached garages, as well as a duct leakage test with a duct air tightness tester. Use an accurate digital manometer (with 0.1 Pascal readings) to pressure map the house. This includes measuring zonal pressures of floor volumes, attic and crawlspace/basement connections, chases, bypasses, wall cavities where stains are occurring, and stack pressures. Carefully measure what pressures are caused by duct leakage and interior-door closure. What are these pressures doing to any combustion zones, such as fireplaces or wood stoves?
  • Look for insulation anomalies behind the walls where the stains appear. These are very common along kneewalls and trayed ceilings. Infrared scans are very useful here.
  • Measure the duct velocity, using ACCA-recommended procedures. Examine the duct system as to material type and integrity.
  • Carefully examine (and, where possible, performance-test) all combustion devices, including gas and wood log fireplaces (be sure to check the chimney), wood stoves, furnaces, and water heaters. Look for signs of soot or cracked heat exchangers. Don’t forget to examine the return air filter.
  • Consider the extreme. One case involved possible contamination from a neighbor’s improperly burning fireplace. Negative pressures in the client’s home were pulling the smoke and pollutants in from next door.
  • Consider “process of elimination” testing. If multiple pollutant sources are present, place several pieces of white acrylic plastic around the house. Eliminate all sources but one; then examine the plastic after several days. Continue until you have eliminated (or identified) all possibilities.
  • Proper diagnostics–and more important, proper repairs– require proper training. Improper repairs can actually make things worse, so if you’re not sure what you’re doing, call someone who has been trained.

Remember, soot stains (especially in new construction) are often the focus of legal charges. Be exacting in your diagnostics and keep accurate records that will stand up in court.