Yesterday’s Home Health Assessment

Allergy Skin Testing

Yesterday I performed a home health assessment for a woman who was referred to me by her allergist.  The woman had her fair share of allergies: dust mites, ragweed, mold and various plant and grass pollens.  But beyond the typical allergy symptoms, the woman was experiencing tightness in her chest and difficulty breathing.  Lung function tests performed by the doctor indicated that she does not have asthma.  The breathing difficulties go away when the homeowner spends more than a few hours away from the home.

In today’s blog post, I want to describe how I personally go about assessing potential indoor air quality problems like these.

The first step is to gather as much information as possible on the symptoms and the home itself.  I like to use a questionnaire so I don’t forget any important questions to ask.

The second step is to walk through the home just making visual observations.  I write down any unusual odors, water staining, or telltale signs of IAQ problems.

Step three is to take indicator measurements to see how the home is performing.  Parameters such as temperature, relative humidity, dew point, and carbon dioxide can indicate if the space is comfortable and well ventilated.  I also like to scan the home with an infrared camera on the inside and outside to help me identify wet spots.  A moisture meter confirms if the camera’s thermal anomalies are in fact wet.  I also like to check pressurization with a smoke pencil so I understand how air is moving through the space.

Based on all the information gathered in the first three steps, at this point I formulate a tentative explanation for what is happening.  This hypothesis will help me target any diagnostic samples to be collected in the home.  The opposite of hypothesis driven assessment is the shotgun approach.  This is where the consultant fires away, measuring anything and everything, with the hope that something will hit the target.  If your clients have several thousand dollars to blow, don’t let me stop you.  However, I recommend a more prudent “sniper rifle” approach.

The homeowner’s doctor was concerned more with the chemicals in the air, rather than the allergens.  After performing the first three steps of the assessment, we decided to approximate the VOCs in the home using a photoionization detector (PID).  Levels were relatively low, in the 500 microgram per cubic meter range.  I communicated some of the limitations of PIDs, namely, their inability to directly measure and identify the individual VOCs.  The homeowner was not satisfied with the limited data from the PID, so she opted to do a more detailed analysis.

I sampled the air with a thermal sorbent tube connected to a low volume pump.  The laboratory will report on individual VOCs present after performing gas chromatography and mass spectrometry (GC/MS) analysis.  I’ll report back on my blog once the results come back in.

By Ian Cull

I'm I.A.N. the Indoor Air Nerd. I'm a speaker and consultant on indoor air quality issues. To learn more about me, click "about" at the top of this page.

3 replies on “Yesterday’s Home Health Assessment”


The metal switch plate can be colder than the surrounding areas. If there is elevated humidity indoors, it can condense on the plate. I don’t know what climate you are in, or which season you are seeing it. I’m guessing you would see condensation and mold growth on the interior side of the plate in a cold climate in the winter. In a hot and humid climate, you would likely get the condensation on the back side of the plate (assuming the building is air conditioned).

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