The fungitoxic properties of four fungicides, alone and in combination, against four different mold fungi commonly associated with indoor air quality problems were evaluated on two different wood species and sheetrock. The fungicides were chlorothalonil (2,4,5,6-tetrachloroisophthalonitrile) (CTL) in a 40.4% aqueous dispersion, disodium octaborate tetrahydrate (DOT) in two different forms - a 40% glycol solution and a 98% wettable powder, and didecyl dimethyl ammonium chloride (DDAC) in an 80% solution. The fungi were Aspergillus niger, Cladosporium cladosporioides, Penicillium brevicompactum, and Stachybotrys chartarum. All fungicide treatments on wood reduced growth, sporulation and discoloration of the mold fungi when compared to nontreated specimens. No single fungicide provided total control of all four fungi on wood. CTL provided the best single-agent protection by totally preventing the growth of C. cladosporioides and S. chartarum and reducing growth of A. niger and P. brevicompactum to low levels. DOT in both forms was very effective against A. niger, but provided only sporadic protection against other fungi. DDAC provided good protection against S. chartarum but was not as effective against the other molds. Combinations of the different biocides were more effective than any single agent. DOT + DDAC totally prevented or greatly reduced growth of A. niger, P. brevicompactum and S. chartarum. Cladosporium cladosporioides was the most difficult organism to control, but even this was achieved when DDAC was increased to 1.0% with DOT. The most consistent control of discoloration, sporulation, and growth of the fungi on wood was obtained with the combination of DOT and CTL. DOT, alone or in combination with DDAC or CTL, was also very effective against the fungi on sheetrock. The results suggest that by using appropriate products, during construction or after water damage, problems associated with the growth of common molds and their potential health effects can be avoided.

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