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      Normal background levels of air and surface mould reserve in English residential building stock: A preliminary study towards benchmarks based on NAHA measurements

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            This paper reports results obtained from a surface (both visually clean and dirty/dusty surfaces) and active (aggressive or activated) air testing scheme on 140 residential rooms in England, without visible water damage or mould growth, along with a few rooms with visible mould growth/water damage tested for comparison purposes. The aim is to establish normal background levels of mould in non-water-damaged interiors to benchmark a normal indoor environment, and in turn when there is a need for further investigation, and, possibly, remediation. Air and surface mould was quantified based on the activity of β-N-acetylhexosaminidase (EC; NAHA). The obtained readings showed a log-normal distribution. 98% of the samples obtained from visually clean surfaces were equal to or less than 25 relative fluorescence units (RFU), which is suggested to be the higher bound for the range which can be used as a success criterion for surface cleaning/remediation in non-problem buildings. Of samples obtained from visually dirty/dusty surfaces, around 98% were below 450 RFU, which is suggested to define the lower-bound for abnormally high levels of mould, rare even on dirty/dusty surfaces. Similarly, around 98% of the air samples were found to have 1700 RFU or below. Values above 1700 RFU are therefore deemed unlikely in a non-problem indoor environment and can be indicative of a possible problem inducing mould growth. The samples with values below 1700 were further divided into three proposed sub-categories. Finally, the obtained RFU values and the suggested benchmarks were compared to those obtained from 17 non-residential indoor environments in Copenhagen tested previously, and the benchmarks that are currently used in Danish national standards, and they were both found to be highly congruent, suggesting that local climate regimes and room functions might not be as influential on indoor mould levels as commonly thought, or that the nuances between England and Denmark in terms of these factors are not strong enough to lead to sizable changes in the typical indoor mould levels in these countries.


            Author and article information

            UCL Open: Environment Preprint
            UCL Press
            13 February 2020
            [1 ] UCL Department of Civil, Environmental and Geomatic Engineering, UCL, UK
            [2 ] Mycometer
            [3 ] UCL Institute for Environmental Design and Engineering, UCL, UK
            [4 ] UK Centre for Moisture in Buildings (UKCMB), UK
            Author information

            This is an open access article distributed under the terms of the Creative Commons Attribution License (CC BY) 4.0 https://creativecommons.org/licenses/by/4.0/, which permits unrestricted use, distribution and reproduction in any medium, provided the original author and source are credited.

            Polygon UK and EPSRC IAA EP/K503745/1

            The datasets generated during and/or analysed during the current study are available from the corresponding author on reasonable request.
            Civil engineering,Environmental engineering,Microbiology & Virology
            mould,surface sampling,active (aggressive or activated) air sampling,NAHA,England,Denmark,Environmental science,Sustainability in architecture and the built environment


            Decision date: 13/2/2020

            Handling Editor: Dan Osborn

            The article has been accepted and it is suitable for publication in UCL Open: Environment.

            2020-09-23 15:16 UTC

            Date: 13/2/2020

            Handling Editor: Dan Osborn

            The Article has been revised, this article remains a preprint article and peer-review has not been completed.

            2020-09-23 15:15 UTC

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