Abstract
BackgroundQuantitative measurements of mould enrichment of indoor air or house dust might be suitable surrogates to evaluate present but hidden moisture damage. Our intent was to develop a house-dust monitoring method to detect hidden moisture damage excluding the influence of outdoor air, accumulated old dust, and dust swirled up from room surfaces.MethodsBased on standardized measurement of mould spores in the 63-μm fraction of house dust yielded by carpets, the background concentrations were determined and compared to simultaneously obtained colony numbers and total spore numbers of the indoor air in 80 non-mouldy living areas during summer and winter periods. Additionally, sampling with a vacuum-cleaner or manual sieve was compared to sampling with a filter holder or sieving machine, and the evaluative power of an established two-step assessment model (lower and upper limits) was compared to that of a one-step model (one limit) in order to derive concentration limits for mould load in house dust.ResultsComparison with existing evaluation procedures proved the developed method to be the most reliable means of evaluating hidden moisture damage, yielding the lowest false-positive results (specificity 98.7%). Background measurements and measurements in 14 mouldy rooms show that even by evaluating just the indicator genera in summer and winter, a relatively certain assessment of mould infestation is possible.ConclusionA one-step evaluation is finally possible for house dust. The house-dust evaluation method is based on analysis of the indicator genera Aspergillus, Eurotium and Penicillium spp., which depend on the total fungal count. Inclusion of further moisture indicators currently appears questionable, because of outdoor air influence and the paucity of measurements.
Highlights
Quantitative measurements of mould enrichment of indoor air or house dust might be suitable surrogates to evaluate present but hidden moisture damage
Because mould spores simultaneously disperse via airborne dust and settle in the environment, results of airborne dust measurements can vary for several factors, most importantly the quantity of settled dust – that is, already accumulated old dust and newly settled dust [6] – and how strong dust turbulence is in a particular environment
Based on the pre-existing one-step assessment model [9] and the sampling results of the UFOPLAN study [32,34], a new one-step assessment model was developed for the evaluation of cultivable moulds in the 63-μm fraction of house dust (Table 1)
Summary
Quantitative measurements of mould enrichment of indoor air or house dust might be suitable surrogates to evaluate present but hidden moisture damage. Our intent was to develop a house-dust monitoring method to detect hidden moisture damage excluding the influence of outdoor air, accumulated old dust, and dust swirled up from room surfaces. Measuring the mould load in air or house dust can be used as an indirect indicator for present but hidden moisture damage. The degree of cleanliness, the frequency of a room being used, the inflow of outdoor air, and the air circulation all exert an influence on indoor-air dust measurements. Hitherto, these aspects have received little attention
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