Fungal spore transport through a building structure
Airaksinen, M., Kurnitski, J., Pasanen, P. and Sepp?nen, O.
2004 Indoor Air, 14(2): 92-104
http://lib.hut.fi/Diss/2003/isbn9512267756/article6.pdf
Airaksinen, M., Kurnitski, J., Pasanen, P. and Sepp?nen, O., (2004), "Fungal spore transport through a building structure", Indoor Air, 14(2): 92-104.
Abstract:
The study carried out laboratory measurements with a full-scaletimber frame structure to determine penetration of inert particles with size distribution from 0.6 to 4 m and spores of Penicillium and Cladosporium through the structure. Pressure difference over and air leakage through the structure were varied. Measurements at moderate pressure differences resulted in the penetration factors within the range of 0.05-0.2 for inert particles, and indicated also the penetration of fungal spores through the structure. The measurements showed that the penetration was highly dependent on pressure difference over the structure but not on holes in surface boards of the structure. The results show that surface contacts between the frames and mineral wool may have a significant effect on penetration. The penetration was approximately constant within particle size rage of 0.6-2.5 m, but particles with diameter of 4.0 m did not penetrate through the structure at all even at a higher-pressure difference of 20 Pa, except in the case of direct flow-path through the structure. Results have important consequences for practical design showing that penetration of fungal spores through the building envelope is difficult to prevent by sealing. The only effective way to prevent penetration seems to be balancing or pressurizing the building. In cold climates, moisture condensation risk should be taken into account if pressure is higher indoors than outdoors. Determined penetration factors were highly dependent on the pressure difference. Mechanical exhaust ventilation needs a special consideration as de-pressurizing the building may cause health risk if there is hazardous contamination in the building envelope exists.
Practical Implications
Measurements at moderate pressure differences allowed determining penetration factors within the range of 0.05-0.2 for inert particles in a size range of 0.6-2.5 m and indicative results with fungal spores confirmed the penetration through the wooden floor structure. Both measurements showed that the penetration was highly dependent on pressure difference and not dependent on holes in surface boards of the structure. The results are likely to show that surface contacts of mineral wool with other building elements may have an important role on the penetration.
This publication in whole or part may be found online at: here.
Airaksinen, M. Laboratory of Heating, Ventilating and Air-Conditioning, Helsinki University of Technology, PO Box 4400, 02015 HUT, Helsinki, Finland, http://lib.hut.fi/Diss/2003/isbn9512267756/
