Basement (crawlspace ) air causing indoor air quality problems

Air quality investigation is a complex task an only rarely the investigator come across immediately obvious answer to a problem. Typical investigation will usually involve sampling for most likely contaminants in the hope that some will be present at the concentration likely to cause the experienced adverse health symptoms. Preparation and consultation with the client is an important part of the investigation as it helps the investigator to select equipment for the most probable contaminants. Once the site is thoroughly inspected various samples are collected to rule out or confirm possible contaminants.

In this particular case the visual inspection of the property did not reveal anything out of the norm. The moisture mapping showed that the whole of the property is dry and does not suffer from internal dampness problems. Sampling for common indicators of indoor air quality such as carbon dioxide, carbon monoxide and ozone showed good results suggesting that these were not the culprits. I have also performed detailed chemical analysis of the indoor air which picked up some common indoor volatile contaminants at very low concentration (14µg/m3). The low concentration of these chemical agents also suggested that the contamination of the indoor air by industrial is unlikely. The detected chemicals were xylene, toluene and ethyl benzene all commonly used in plastics, rubber , solvents and paints and could be quite confidently linked to recent re-decoration and generally to household items. Other group of chemicals detected in the property contained pipene and cyclopropylnorcarene both associated with scented products such as fragrances, perfumes and cosmetics and in the case of pipene also naturally occurring in the outside environment.


Chemical sampling in the crawlspace of the property

First clues about what might be amiss came from the long term humidity and temperature data loggers. Monitoring over a week showed that the property had unusually high humidity which was more or less constant and independent of the outside environment. The measured humidity levels throughout the property ranged between 64% and 67% which is at the very top of the acceptable range. Another clue came from particle sampling at the property. Although the absolute concentration of airborne particles in any property is of very little value the relative difference in particle concentration can point out areas warranting further investigation.  During particle sampling I have noticed that in the foyer area of the property the particulate concentration was an order of magnitude higher than anywhere else in the property.

Based on these preliminary results I have collected further samples for both analysis of airborne fungal elements and also for forensic analysis of the dust particles. The mould spore samples showed that the concentration of mould (fungal) fragment and spores was in quantitatively less than the outdoor samples and qualitatively identical to the outdoor samples. This indicated that most of the fungal elements detected indoor originated outdoor. Forensic analysis of the dust did not show any abnormalities in dust composition.

The investigation of has not yield any positive results but as with any other investigation even no results are results. The absence of an obvious source helps me to focus my attention of aspects of indoor air quality not commonly encountered. My attention switched to the construction of the house as a whole an in particular to the crawlspace under the property. Inspection of the crawlspace again did not reveal an immediately obvious problem, the crawlspace was empty of any materials and well ventilated. The only abnormality was the presence of a relatively small patch of wet ground (10m2) right under the hatch area. I have observed a relatively strong odour emanating from the ground suggesting active microbiological activity and also quite a strong air flow from the nearest air vent into through the hatch into the property.


Visibly damp section of the dirt floor, noticalbe odour was present in this area

In the end the most likely problem in this property causing respiratory irritation in one of the occupants was the constant ingress of damp air from the property’s crawlspace into habitable areas. The air was passing over the damp area picking up various microbiological volatiles some of which are know irritants. The fact that only one of the occupants of the property felt any symptoms suggested that the person in very sensitive and that the contaminants must be present at very low concentration.

The recommended solution to this problem was the isolation of the dirt floor by water resistant membrane to prevent the contamination of indoor air by air passing through a crawlspace.

You can read more about crawlspace air and how it travels into the property in this article.

By Tomas Gabor

Link through to Sysco - Nationwide specialists in hazard exposure monitoring
Hi, I have been working in my job as an Indoor Air Quality Investigator for a number of years and decided to share my experience with you. You can find lot of related information on my website toxic black mould
Leave a comment
  • ralph

    I was wondering what could be making me so ill, thanks for the idea I will investigate

    December 20, 2013, 7:30 am permalink
  • MircooW

    What kinds of pollution can be coming into my house from crawlspace under he floor boards?

    December 20, 2013, 12:29 pm permalink
  • linda

    interesting post, i will look into our basement to see what is going on, i’ve ben supecting this kind of issue for a long time. thanks

    December 21, 2013, 3:24 am permalink