Tests to identify building stains: this article describes methods for diagnostic testing of interior stains on buildings. While we can usually identify the key components of a building stain by appearnce, location, surroundings, & apparent cause, some stains & marks in or on building materials & surfaces can be ambiguous and some may represent harmful or even dangerous contaminants or unsafe building conditions.
Much confusion occurs among dark stains, smudges, and "toxic black mold" or among white or brown or yellow "growths" and mineral efforesence. Usually actual laboratory testing is not warranted, but on occasion, such as when facing major expense or when needed as a building health or IAQ diagnostic, such tests can be useful.
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Rule out natural color variations: Some apparent building stains may not be an actual stain at all but rather the original color or color variations in natural materials such as the birch plywood door shown at left. Sometimes what you think is a new building stain is actually a color variation that has been in place for some time, but was not previously attended.
Identify thermal tracking stains from normal house dust: If you are able to rule out specific air leaks causing normal deposition of house dust, and if you are quite sure that you have an abnormal level of stains/soot like material showing up on various surfaces then these courses of investigation are suggested as an aid to diagnosing stains on indoor ceilings, walls, floors, carpets, cabinet interiors, closet interiors, or even house contents:
How to Separate normal "thermal tracking" dust deposition patterns from other types of indoor staining
If stains or debris are appearing on surfaces which are not cooled by their location (such as exterior walls, hollow interior walls which are entertaining internal air movement due to convection from below to above, areas near cooling air registers), then it may be possible to state with confidence that the stains appearing are due more to a high level of particulate debris in the building than to the more common thermal tracking phenomenon (THERMAL TRACKING & THERMAL BRIDGING). .
How to Perform Dust or Soot Source Testing & Source Identification
Look for the source or potential sources of abnormal levels of indoor airborne debris, soot, particles, dust, such as a malfunctioning oil or gas fired appliance, any other combustion sources, even a mal-adjusted pilot light on gas stoves or heaters can be a soot source as well as the oft cited candles, fireplaces, and even pets (for example lots of dog traffic between indoors and out brings in high levels of dust).
If/when we can identify an unusual source or a source producing an unusual level of particulate debris we have perhaps answered a key part of this question of the probable source of indoor soot, dust, or debris stains.
Measure Indoor Moisture Levels when Diagnosing Indoor Stains and Soot or Debris Deposits
OPINION: even in a relatively clean home, unusually high moisture levels may result in noticeable levels of dust deposition on indoor surfaces, regardless of the dust source, and even including normal types and sources of house dust.
If moisture levels are a factor in the home, say moisture regularly above 55% RH, we would expect to see more-stained surfaces on those building surfaces that are more likely to be a bit higher in moisture, such as cooler surfaces on walls, ceilings, or in closets or cabinets where temperatures are lower and moisture may condense at a slightly higher level.
Indoor Stain Diagnosis Using Air Movement Patterns
Sometimes we can identify particular sources of air movement, directions of air movement, which we can correlate with the areas where we see staining. A simple example is the higher amount of dust deposition that occurs around heating or air conditioning supply registers on ceilings and walls. Relating air movement patterns to dust or soot or other debris stains may be diagnostic.
Also take a look at a short paper we wrote on an analysis of suspect indoor dust, at An Investigation of Indoor House Dust Debris where we determined that indoor dust levels which had been suspected of originating in an HVAC system were actually carpet dust and fibers.
How to Use Particle Identification to Diagnose the Source of Dust, Dirt, Soot, or Debris Stains
It is often possible to collect samples of suspect dust or debris for microscopic analysis in order to suggest a source or type of source of indoor stains.
It is essential that you select a forensic laboratory whose staff includes people experienced and trained in the identification of a wide range of indoor particles. A lab specializing in mold or allergen identification, for example, may not consider much less apply methods used to identify oil burner soot, common components of ordinary house dust, mite fecals, pet dander, human skin cells, fabric fibers, or other indoor particles which, if properly identified along with a statement of relative frequency in the sample, may be diagnostic.
How to Collect Indoor Dust, Debris, or Stain Particles for Microscopic Lab Analysis
How to Collect Samples of Stains, Dust, or Debris on Hard Surfaces
For particles or stains found on hard surfaces indoors such as walls, ceilings, or furniture, often a simple adhesive tape sample will perform best. Furthermore, this sampling procedure is itself diagnostic, since if the adhesive tape is unable to lift and collect any particles from the surface, that also tells us something about the type of staining present.
But remember that even an apparently "clear" tape sample (when viewed by the naked eye) may contain important diagnostic particles which will be quite evident when viewed as a properly prepared microscopic sample and at proper magnification and lighting in a forensic microscope.
See Six Easy Steps to Get and Mail a Mold Test Kit to Our Lab for 24-Hour Analysis and Report for a surface sampling procedure using adhesive tape. You can use this sampling method to collect surface particles for submission to any qualified forensic laboratory not just ours.
How to Collect Samples of Stains, Dust, or Debris from Soft Surfaces like Carpets or Furniture
Details about particle collection using adhesive tape or vacuum cassette test methods for carpet debis or stain or suspected-mold contamination are detailed
Qualitative analysis of dust and debris: We use an air-sampling cassette connected to a vacuum pump to collect debris from carpets, upholstered furniture, or carpets. In the hands of an experienced investigator a useful non-quantitative analysis can be performed to collect particles which, examined in the lab, can tell us the dominant particles present in the debris.
The lab should also be asked to cite other particles, even occurring at low levels, if the particle type is particularly diagnostic of a potential indoor air quality problem. An example is the presence of chains of Penicillium/Aspergillus mold spores since when found occurring in chains, these spores are suggestive of a nearby (potentially toxic or allergenic) mold contamination problem.
Quantitative analysis of house dust: other vacuum methods which use a calibrated flow rate and a sampling filter can collect nearly 100% of the particles from a surface, permitting a quantitative analysis of the number of particles per square inch. In our OPINION this is often a rather questionable procedure.
Watch out: Even studies which claim to report that the results of this sampling method are repeatable (a measure of sampling method reliability) we find that there is an enormous variation, probably several orders of magnitude, in the number and possibly even the type of particles collected in such samples depending on the investigator's choice of sampling location, sample duration, vacuum strength, and other factors.
The result may be an analysis which is impressive in its precision, say giving 1,243.275 particles of particle type X per square inch of surface, but completely inaccurate (because there maybe so much variability due to sampling procedure that sampling an area one foot away gives a particle level of 124,327.5 particles per square inch.).
See PHOTO GUIDE TO STAINS on Indoor Surfaces for examples of some common types of indoor stains on HVAC registers, doors, carpets.
Usually soot marks, thermal bridging, or thermal tracking stains appear, if at all, in the building interior locations listed just below discussed in the THERMAL TRACKING BRIDGING GHOSTING article series.
Continue reading at CARPET TEST PROCEDURE or select a topic from the More Reading links shown below.
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We welcome more thermal tracking, soot tracking, air bypass leaks, and similar photos of indoor stains as well as text suggestions to expand this detail and would be glad to credit contributors.