Mechanical exhaust ventilation system is typical in apartment buildings in Finland. In most buildings the base floor between the first floor apartments and crawl space is not air tight. As the apartments have lower pressure than the crawl space due to ventilation, contaminated air may flow from the crawl space to the apartments. The object of this study was to find out whether a potential air flow from crawl space has an influence on the indoor air quality. The results show that in most cases the concentration of fungal spores was clearly higher in the crawl space than inside the building. The size distribution of fungal spores depended on the fungal species. Correlation between the fungal spores in the crawl space and indoors varied with microbial species. Some species have sources inside the building, which confounds the possible relation between crawl pace and indoor concentrations. Some species, such as Acremonium, do not normally have a source indoors, but its concentration in the crawl space was elevated; our measurements showed also elevated concentrations of Acremonium in the air of the apartments. This consistent finding shows a clear linkage between fungal spores in the indoor air and crawl space. We conclude that a building with a crawl space and pressure difference over the base floor could be a potential risk for indoor a ir quality in the first floor apartments.

Practical Implications

Mechanical exhaust ventilation causes an under pressure to the apartment and, thus, air flow from crawl space to indoors may occur. Very often some contamination in a crawl space exists and according to these measurements fungal spores are transported indoors. It seems that a ventilation system causing an under-pressure inside apartment might be a potential health risk, thus, a balanced ventilation system is recommended.

• particle transport, penetration of particulate, through walls

1. Fungal spore transport through a building structure
2. Moisture and fungal spore transport in outdoor air-ventilated crawl spaces in a cold climate  

1. Can microbial volatile metabolites cause irritation at indoor air concentrations?
2. Effect of duct-cleaning detergents and disinfection substances on mould growth
3. Ergosterol content in various fungal species and biocontaminated building materials
4. Fungal growth on wood surfaces at different moisture conditions in crawl spaces
5. Fungal spore transport through a building structure
6. Growth and volatile metabolite production of Aspergillus versicolor in house dust
7. Significance of air humidity and air velocity for fungal spore release into the air
8. Transport of fungal spores from crawl space to indoors
9. Volatile compounds originating from mixed microbial cultures on building materials under various humidity conditions
10. Volatile organic metabolites associated with some toxic fungi end their mycotoxins  

1. Crawl space air change, heat and moisture behaviour
2. Crawl space types and building physics
3. Facade design principles for nearly zero energy buildings in a cold climate
4. Fungal spore transport through a building structure
5. Humidity control in outdoor-air-ventilated crawl spaces in cold climate by means of ventilation, ground covers and dehumidification
6. Indoor humidity loads and moisture production in lightweight timber-frame detached houses
7. Moisture conditions of outdoor air ventilated crawl spaces in apartment buildings in a cold climate
8. The effects of ventilation systems and building fabric on the stability of indoor temperature and humidity in Finnish detached houses  

1. Association of ventilation system type with SBS symptoms in office workers
2. Fungal spore transport through a building structure