Mould growth on building materials - Statens Byggeforskningsinstitut

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inorganic concrete materials partly supported germination of especially A. versicolor and sterilia mycelia at RH >90% and <strong>growth</strong> at 95%, as seen in Figure 6. This must be due to trace quantities of organic components in the concrete. As the concrete materials were cleaner than the ones used in buildings concrete based materials will probably support more <strong>growth</strong> under field conditions (paper 10). When comparing Tables 2 and 3, it is clear that the temperature drop from 10 to 5°C had a dramatic effect on the fungal <strong>growth</strong>, showing no <strong>growth</strong> at 90% RH and 5°C, and that also here was wooden and the wallpapered materials the most susceptible (paper 10). 4.2.1 Methods for testing the susceptibility of materials As mentioned in the literature part, testing materials for their susceptibility is difficult, even just controlling the humidity is difficult. As this was the first time such a test was performed at the Danish Building Research Institute, it was tried Ventilator Hygrostate to keep the set-up as simple Flow controllers as possible (paper 10), and 90% RH 80% RH regard the study as a pilot Water bath project which should ex- 1.2 m Exhaust plore difficulties such as humidity range, inoculation, 1 mm and especially assessment Sample box Sample of the materials. This set-up is shown in Figure 7, and was primarily built by Gunnar Holm. Initial conditions may play an important role for the surface aw of the materials, and as it was desired to use steel chamber and take the materials out for assesment, it was necessary to use the sample boxes for reasons occupational health. This meant that the surface aw would be controlled by the RH of the incoming air to the sample box and primarily by the absorbance of water by the material until equilibrium, which small experiments had showed would take months. This meant that we had to add the quantity of liquid water to the materials, assuming that it would be equally distributed within a few days. Although this should tested in future experiments. I paper 13, the set-up at TNO Bouw was used, and the initial humidity was controlled by a high continuous airflow over the materials (see Figure 8). This means that the absorption of water from the airflow was so little that the change in humidity over the 10 materials in each channel could be neglected. However this approach created another problem as the air speed itself can inhibits <strong>growth</strong> if the speed is too high. This is illustrated in Fig- 3 Dry air 0.1 m /hr air 3 Dry air /hr air Figure 7. The fungal <strong>growth</strong> assesment set-up used in Paper 10. ure 9, where the air speed was higher in one side of the channel than in the other. The TNO approach (paper 13) had another advantage, as it is possible to work with transient humidity conditions, and here it Page 33 Figure 8. The TNO set-up, 10 material in each row. In this case infested with P. chrysogenum.
was seen that the stress of using periods of high and low humidity during a day, trying to mimic a bathroom. This had a strong selectivity stress towards the phylloplane, Cladosporium, which under transient conditions was able to outgrow P. chrysogenum. The instationary conditions, with and without surface condensation (paper 13), can cope with conditions which keeps the storage moulds away and still be too dry for the phylloplane. It can also cope with water accumulation in the surface of materials, especially when working with two to three layer systems, like a painted piece of cardboard gypsum (3-layer system) 11 . Hence, the total <strong>growth</strong> behaviour of materials is extremely complicated, and to characterise a material well, the performance and associated funga under at least three different environmental conditions is needed: • The lowest RH which supports <strong>growth</strong>. • The performance under transient conditions. • The performance under water damage. 4.2.2 Growth assessment In paper 10, the materials had to be taken out of the set-up for assesment. This was very time consuming and obscured the environmental conditions for the samples. Using the approach of Adan 11 as in Paper 13 (see Figure 8), the materials can be assessed several times a day if required. The time resolution of this process describes the susceptibility - as how fast <strong>growth</strong> started - better than endpoint determinations of biomass. The latter parameter seems to describes how much of the substrate could be utilised (papers 10 and 13). Visual inspection (paper 13) has a major problem, especially using the 5 point scale described by British Standard 411 , as the assessed coverage area is the output parameter. This does not take the concentration of fungal biomass into account. Thus a material with very light coverage over all of the material will be assessed to have a higher value than a material with heavy <strong>growth</strong> over only a part of the material. The use of image analysis was partly explored at the stay at TNO Bouw (unpublished), and this technique will undoubtedly help in future studies, as images for assessing the materials can be taken automatically several times a day. It can also cope with the high <strong>growth</strong> rate observed on some paints (where the materials had to be assessed 2- 3 times per day, paper 13). Also a more standardized assessment including the fungal "concentration" can be made. However this will require that the image-analysis is calibrated carefully against very welldescribed samples. Here chemical markers could help to compare the appearance of different moulds. The use of dissection microscopy showed that the moulds often grew in mixtures (see Figure 10). Looking at materials with scarce <strong>growth</strong> and a fibrous surface was very difficult, and only sporulation could be detected. However it was possible to distin- Page 34 Figure 9. The influence of too high air velocity on A. versicolor <strong>growth</strong> in one side of the set-up. Figure 10. Mixture of A. flavus, A. versicolor and P. chrysogenum, growing on pinewood.
Page 1 and 2: Ph.D. thesis Mould
Page 3 and 4: Title Mould <stron
Page 5 and 6: 4.3 Growth and metabolite productio
Page 7 and 8: Mould grow
Page 9 and 10: ABSTRACT The aim of this study was
Page 11 and 12: ABBREVIATIONS AND TERMS Aflatoxin B
Page 13 and 14: PAPERS PREPARED IN CONNECTION WITH
Page 16 and 17: 1 INTRODUCTION During the last 10 y
Page 18 and 19: 2 MOULDS IN BUILDINGS Viable mould
Page 20 and 21: of Penicillium and Aspergillus vers
Page 22 and 23: 2.2.1.1 Humidity - some definitions
Page 24 and 25: current PC programs which can model
Page 26 and 27: the scope of this work, and only ca
Page 28 and 29: It should be considered that on nat
Page 30 and 31: Europe produced MTR. This is signif
Page 32 and 33: een Japanese patents and patent app
Page 34 and 35: 2.4.2.2 A. ustus Aspergillus ustus
Page 36 and 37: 2.4.3.2 P. brevicompactum Penicilli
Page 38 and 39: and the altertoxins are about 1000
Page 40 and 41: Erg is partially bound as different
Page 42 and 43: ionisation (APCI) have greatly expa
Page 44 and 45: genera Penicillium, Aspergillus, Al
Page 46 and 47: 4 RESULTS AND DISCUSSION The reason
Page 50 and 51: guish A. versicolor, often seen as
Page 52 and 53: These findings are in accordance wi
Page 54 and 55: To study the ratio between trichode
Page 56 and 57: When growing on PSA agar, S. charta
Page 58 and 59: These quantities correspond to abou
Page 60 and 61: Two different growth</stron
Page 62 and 63: mAU 4 3.5 3 2.5 2 1.5 1 0.5 0 mAU 1
Page 64 and 65: 4.3.2.4 A. flavus In paper 10, A. f
Page 66 and 67: 4.3.3.3 P. polonicum Only two indoo
Page 68 and 69: 4.3.7 Chaetomium globosum Being an
Page 70 and 71: 4.3.11 Eurotium In study 10, Euroti
Page 72 and 73: makes screening impossible, as it p
Page 74 and 75: 5°C. Pure mineral based materials
Page 76 and 77: REFERENCES 1. Platt,SD, Martin,CJ,
Page 78 and 79: 44. Jarvis,BB, Sorenson,WG, Hintikk
Page 80 and 81: 87. Nevalainen,A, Pasanen,A-L, Niin
Page 82 and 83: 135. Jakubowski,J. 1971. The prewea
Page 84 and 85: 176. Ueno,Y. 1985. Toxicology of My
Page 86 and 87: 223. Kaneto,R, Dobashi,K, Kojima,I,
Page 88 and 89: 264. Land,CJ, Hult,K , Fuchs,R, Hag
Page 90 and 91: 307. Shier,WT, Abbas,H, Mirocha,CJ.
Page 92 and 93: 353. D'agostino,PA, Provost,LR, Dro
Page 94 and 95: 392. Hack,R, Märtlbauer,E, Terplan
Page 96 and 97: APPENDIX A Conference proceedings a
Page 98 and 99:
Table 2 Non-trichothecene secondary
Page 100 and 101:
Table 3 Secondary metabolites and m
Page 102 and 103:
Page 104 and 105:
Page 106 and 107:
Page 108 and 109:
Table 10 Secondary metabolites and
Page 110 and 111:
Table 14 Secondary metabolites and
Page 112 and 113:
Reference List 1. Anonymous1991. At
Page 114 and 115:
69. Hamaski, T, Hatsuda, Y, Terashi
Page 116 and 117:
137. Ghosal, S, Biswas, K, Chakraba
Page 118 and 119:
205. Castillo, M-A, Moya, P, Couill
Page 120 and 121:
269. Brückner, H, König, WA, Grei
Page 122:
Mould grow
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