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:
- “Highly elevated levels of fungi spores (mold spores) were found…” Further, some of the spores identified were listed as;
- “Considered to be toxic and may cause serious health risks.” Further in the report, the hygienist goes on to say that;
- “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.
- “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:
UNSAFE AND CONTAMINATED! HIGHLY ELEVATED LEVELS OF MOLD SPORES; SOME OF WHICH WERE CONSIDERED TOXIC.
this was wrong and our case study on inaccurate air samples shows you why!
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.
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.
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.
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.
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.
5 replies on “Case study on inaccurate air samples”
I don’t even know how I ended up here, but I thought this post was good.
I do not know who you are but certainly you’re going to a famous blogger if you aren’t already ;
Hi to all, the contents existing at this web page are truly awesome for people knowledge, well, keep up the nice work fellows.
thank you for the kind words.
April 7, 2012Thank you for the sensible ciirtque. Me and my neighbor were just preparing to do a little research on this. We got a grab a book from our area library but I think I learned more from this post. I’m very glad to see such fantastic info being shared freely out there.
Thanks Silvia. I’m glad this could help.