Real estate transactions Uncategorized

Case study on inaccurate air samples

 Case study on inaccurate air samples

Location- Santa Barbara California 

Problem:  Our case study of inaccurate air samples is centered on a home in escrow for $3.9 million dollars that was re built from the ground construction budget was $2.5 million dollars.  In connection with the escrow and proposed purchase, a mold inspection was performed by industrial hygiene company.  In their inspection they identified no problems in the home with respect to mold.  Their principal focus was NOT the investigation but to collect exhaustive air samples from inside of the home; although an inspection was performed and they could NOT identify any issues visibly.  Several air samples were collected and the results of those samples revealed severe anomalies and elevated mold spore counts in the home directly causing the prospective purchaser to cancel the transaction.   The couple who owned the home were told by the Mold inspection company that since they found such high levels of mold spores, but could not find any issues, that the only solution to solve this was to literally remove every interior wall from the framing and strip the house.  Their bid was in excess of $150,000 dollars for this work and it was estimated that replacing the removed finishes would cost between $250-350,000 dollars depending upon what materials would be used.  This is why we wrote this case study on inaccurate air samples.

Location: Single family residence, Santa Barbara California near the ocean.

Construction: Complete ground up, new construction.  Raised foundation single family two story home.  Ample crawl space that was observed to be damp and have strong musty odors.

Crawlspace description/openings: The crawl space under the home contained several openings from understructure into home (“thermal bypasses”) enabling for routing air exchange between the foundation and the interior air space of the home.

Observations in the initial report:  While the inspection appeared somewhat comprehensive with respect to sample data, there were several deficiencies in the investigation itself.  Further, the single largest issue is that the inspection company identified the substructure of the premises as being on “slab foundation” and not a suspended foundation with a crawl space.  Clearly the company (name withheld) was incorrect.

Conclusions of their report which caused the transaction to fail:

Our case study on inaccurate air samples shows that after not identifying any issues the hygienist elected to collect “precautionary air samples” in order to assess if there were issues in the home with respect to mold problems.   The results of the air samples collected showed several anomalies (problems) in the indoor air quality and caused the attending hygienist to conclude:

  1. “Highly elevated levels of fungi spores (mold spores) were found…”   Further, some of the spores identified were listed as;
  2. “Considered to be toxic and may cause serious health risks.”   Further in the report, the hygienist goes on to say that;
  3. “A trained professional should identify any associated water source that led to the problem”   Although the report itself did NOT identify any issues in the home nor any areas that appeared to be impacted by elevated moisture content in the building materials.
  4. “No areas of elevated moisture levels were detected at the time of the inspection.”

Although the hygienist doing the inspection could not identify any issues, he concluded that the home was:


this was wrong and our case study on inaccurate air samples shows you why!

Our analysis:

We briefly examined the home in light of the air sample data collected and the conclusions of the report.  In examining the laboratory data collected in the previous inspection we observed that the air in the lower area of the home appeared to be significantly worse than elsewhere in the home; although all areas inside of the home appeared to be compromised.  Immediately we were able to determine that the previous hygienist incorrectly categorized the construction type of the premises as being built on slab when in fact there is a crawlspace below the lower level that spans the entire portion of the lower area of the home.  Upon examination of the crawlspace itself the area was damp, musty and in need of drying.  Further, when we examined the underside of the rooms on the lower level we identified several openings from the crawlspace up into the lower area of the home.  The openings observed were both for routing conduits as well as simple random open spaces and unsealed areas.  When openings from the crawlspace to the lower floor are present, this provides an easy path for air exchange between the crawlspace and the interior living space of the home.  Simple physics (temperature differences) causes air molecules to be attracted upwards into the interior living space of the home.

This is an example of a typical opening observed in the understructure of the home.  There were other openings and areas in the crawlspace that enabled air exchange between the foundation and the interior of the home.

case study on inaccurate air samples

Our Action Plan:

After a brief examination of the premises we concluded that indeed the reason for the elevated levels observed in the initial study was on account of the air exchange between the crawlspace and the interior of the premises.  Our mitigation plan included, but was without limitation to, the following steps:

1)      The entire premises was professionally HEPA vacuumed using commercial grade HEPA rated HEPA vacuums.  This included all of the lower and upper areas of the home, bedrooms, bathrooms, closets, cabinet interiors and exteriors, light fixtures, detail finish work.

2)      All horizontal surfaces and walls in the entire home were wiped with a mild surfactant to remove any dust that may have had mold spores attached.

3)      Commercial grade 500 CFM HEPA filters were placed inside the home during the above cleaning to trap any spores released during the cleaning process.

4)      The carpets inside the home were professionally cleaned and then again after the cleaning professionally HEPA vacuumed.

5)      Negative pressure was established under the home in the crawlspace using 500 CFM commercial grade HEPA filters and taping off access points of the crawlspace.

6)      Any damp moist soil turned over and/or removed from the area.  Any organic materials or soil that appeared to have organic materials in it was removed and disposed of.

7)      The understructure was wiped down in any areas that appeared to have any physical organic material on them.  All mold present in the understructure on substrates (other than the dirt itself) was sanded, cleaned and disinfected.

8)      All openings from the understructure up into the home were sealed off with self-expanding foam and or silicone caulk.  Larger areas where openings existed building materials that were pretreated with mold resistant sealer were applied to the openings and sealed using silicone caulk.

9)      Understructure fans were installed inside of the crawlspace with the intent to assist in keeping the crawlspace dry and free from moisture and create negative pressure under the crawlspace which would remain constant.  This would assist in preventing any air exchange from the crawlspace into the home.

An example of a typical patch placed on the underside of the crawlspace sealing off the opening up into the home.

case study on inaccurate air samples

Image of fan installation and wide view of crawlspace in the home.  Note that 3 fans were installed and air flow was directed out of the crawlspace vents on 3 sides of the foundation.

 case study on inaccurate air samples

Our Laboratory Results:

The air samples we collected after sealing off the openings to the crawlspace showed a dramatic improvement in the indoor air quality of the home and no abnormalities with respect to elevated mold spore counts were identified.

case study on inaccurate air samples

The table represents the total spores per cubic meter of air as compared to the outdoor sample collected at the time of each air quality study.  In the initial air quality study the total spore counts inside were between 107% and 318% of what was identified as present in the general atmosphere at the time of the study.  The downstairs guest room being the worst should more than 3 times the number of spores present inside the room as compared to outside.  Right behind that was the master bedroom which showed 285% of the spores found outside.  After the understructure was sealed and the openings from home into the crawlspace closed off our air study showed a dramatic increase in indoor air quality and reduction of mold spores.  In our study we found only 25% number of spores in the downstairs guest room as compared to the general atmosphere at the time.  This represents a 1260% increase in indoor air quality.  Similar dramatic increases were observed in the other rooms of the home.

In analyzing indoor air quality, samples are collected in various rooms and an outdoor control sample is collected.  The spore counts per cubic meter of the individual samples are compared to the spore counts per cubic meter of the outdoor control sample.  As the general composition of mold/pollen spores changes day to day with atmospheric conditions you cannot simply evaluate spore counts by themselves inside of a home but rather in context with the general outdoor conditions present at the time of the sample collection.  In making a true “apples to apples” type comparison, the table above represents the analysis in context with the original control sample collected.  Both sets of air samples were processed by the same laboratory.


The initial study did not take into account that design and construction issues that existed; namely that openings to the understructure were present allowing air exchange between the crawlspace of the home and the interior air space.  Initial air sample analysis confirm this.  After the understructure openings were sealed off and the resultant spores which had entered the home removed via thorough cleaning and the indoor air quality of the home showed to be in good condition.  A dramatic improvement of up to 1260% was seen when the openings from the crawlspace into the home were sealed off.

The collection of air samples confirmed that the air exchange between the crawlspace and the interior of the home was the root cause for the observed elevated spore counts.





Real estate transactions Uncategorized

How a crawlspace impacts indoor air quality

How a crawlspace impacts indoor air quality

How a crawlspace impacts indoor air quality

How a crawlspace impacts indoor air quality

This image illustrates how air moves through you home!

this article will help you understand how a crawlspace impacts indoor air quality of your home.  Air moves in and out of your home via pathways and typical gaps in insulation and construction that are not sealed.  This shows how a crawlspace impacts indoor air quality.  As energy efficiency increases, air exchange decreases resulting in less fresh air coming into you home!  Which is responsible for having stale air in your home.  This is why we suggest every home have an ERV.  See our article on ERV’S.

How a crawlspace impacts indoor air quality!

So if you have an understructure in your home, you can bet that it is in some way impacting your indoor air quality.  This is really an easy fix.  Under structure fans, sealing off openings will fix this problem.  Crawlspaces can have a dramatic impact on air samples as this one Santa Barbara couple found out when selling their home when it killed their multi million dollar sale!  See our article on inaccurate air samples. 


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Real estate transactions Uncategorized

Do I need air tests during my mold inspection?

Do I need air tests during my mold inspection?

Do I need air tests during my mold inspection? The answer on the first time inspection is typically no!  Air tests are valuable tools that an industrial hygienist (mold inspector) can use.  If you don’t take air samples how do you know?  The answer is simple as well as complex.   But in essence, if you FIND a problem during your inspection, there isn’t much reason to spend money to find out what you already know.  Further if there are design or construction defects in  your home, poor ventilation, maybe even something as simple as a front load washing machine having mold in the door gasket, these things will ALL through off air sample results.  Even something as benign as cutting the grass before you take the outdoor sample will cause the outdoor sample to have very high readings which will skew the analysis when comparing to the indoor air sample counts.  Some issues with air samples can be:

  • Results and conclusions are subjective- most people (even laboratories) don’t understand how to accurately compare indoor and outdoor spore counts and read the results-
  • Conditions impact results-  Typically and indoor sample is compared to an outdoor sample and the comparison determines the “issue” or lack thereof inside the room.  If it is windy, or there is old wood, lots of foliage or  other atmospheric conditions that may exist these can all cause the “control” (outdoor sample to be in accurate).  This outdoor sample is what you use to contrast with the indoor sample to make a determination.
  • Data is interpreted and NOT pass fail-  non-viable Air samples (which represent 98% of all air samples collected) are interpreted.  They are not empirical. So there is some individual who is making a subjective judgement on many things that impact the labs ability to actually read the slide from the sample.
  • Collection methods can impact results- Depending upon where the control sample (outdoor sample) is taken could dramatically impact its result and thereby making the interior sample comparison inaccurate.  This is a huge problem
  • False positives/False negatives-  Design and construction defect such as openings that allow air from under the home to enter the home can dramatically impact the spore counts inside of the home.  See our article on how a crawlspace impacts your home for more information on this.
  • Cost a lot of money and only tell you what you should already know

Do I need air tests during my mold inspection?

Do I need mold tests during my inspection?

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Do I need air tests during my mold inspection?

Taking air samples is the default for companies who do inspections and don’t know how to do a comprehensive site investigation.  It is the “easy way out”  The logic is that if it isn’t in the air, it isn’t there is foolish!  The answer is to perform a complete physical examination and moisture analysis.  IF there is mold found, remove it plain and simple!  Don’t be fooled into thinking that you have a GREAT deal because you get air samples.  Worse yet, what happens if you take air samples and they are positive?  What do you fix?  THIS IS NOT what a competent mold investigation should tell you.[/one-half]


Do I need air tests during my mold inspection?  Some of the issues with air samples can be:

  • Results and conclusions are subjective-  With air samples an indoor sample is compared to an outdoor sample.  Concentrations of various types of spores are compared as are total counts.  However, conditions greatly skew these results.  Circumstances like wind, debris on the slide and personal bias impact how results are gathered and interpreted.   While air samples can be useful, they should NOT be relied upon to make a decision either way.
  • Conditions change from moment to moment-  We have participated in over 40,000 inspections many of them with air samples.  One common theme of all of the samples we have collected is that results vary widely from moment to moment.  We have seen rooms that have mold literally coated on the walls from floor to ceiling as thick as Christmas Tree flocking and have had the air tests come up NEGATIVE.  We have seen other circumstances where air tests are positive and there is nothing wrong at all.  Air tests are tools but they should not substitute for a good, comprehensive physical inspection by someone who specializes in mold investigation.

Air tests should not be taken in a home that has a raised foundation or crawlspace!

Homes that have an understructure or crawlspace have openings which afford air exchange between the crawlspace and the interior rooms/floor above.  In a Duke University study, they concluded that in a typical home with a crawlspace, as much as 70-80% of the air inside the home has passed through the crawlspace!.  ALL crawlspaces are not good.  There is bacteria, mold and all sorts of stuff present in almost every crawlspace.  Why would you want to breath air from your crawlspace? you shouldn’t.  But this is why if you have a crawlspace, taking air samples inside of a home, will likely only tell you that mold spores (present in EVERY crawlspace) are coming into the home via pathways from electrical, plumbing conduits and other openings into the interior that are not sealed.

Here are some examples of openings that allow air exchange in a typical home

Do I need mold tests during my inspection? Do I need mold tests during my inspection? Do I need mold tests during my inspection?

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So, you think you have mold

3d human with a red question mark

So you think you have a mold issue?  We can help you figure it out.

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