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![Mold growth index of Xerophilic fungus. Circle: germination within 24 hours; square: germination 2 to 7 days; triangle: germination 8 to 30 days. The number on the figures are fungal indices [ru/week]](profile/Mohammad-Heidarinejad/publication/266375006/figure/fig4/AS:392137611988996@1470504300622/Mold-growth-index-of-Xerophilic-fungus-Circle-germination-within-24-hours-square.png)
Mold growth index of Xerophilic fungus. Circle: germination within 24 hours; square: germination 2 to 7 days; triangle: germination 8 to 30 days. The number on the figures are fungal indices [ru/week]
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Small-scale air–water experiments reported here contain all the important features of the industrial caster, the mold feed pipe, and the nozzles associated with it. The liquid is introduced into the feed pipe through an annulus with the gas entering at the center. The liquid travels down the walls of the feed pipe as a film until it encounters the...
Citations
... The ventilation systems are mostly made of inorganic materials, but the ductwork may accumulate dust, outdoor contaminants or moisture during use. If the system is contaminated, the air supplied by it may include fungi spores and bacterial colonies [15][16][17]. ...
High humidity inside ductworks could be a potential risk for microbial growth and there is also a hypothesis that lower night-time ventilation increases the risk of growth. This study investigates the possibility of microbial growth in ventilation ductwork exposed to humid and cold conditions. Two different typical night-time ventilation strategies for public buildings were investigated: ventilation rate was either continuously the same (0.15 L/s, m2) or no airflow during the night-time. Experimental data were collected over a four-month period. In the experiment, microbial media was released inside the ductwork initially. During the test period, air temperature and relative humidity inside the ductwork were controlled between 11–14 °C and 70–90%. Wipe, swab and air samples were taken at the beginning, monthly and at the end of the test period. The study results showed the extinction of colonies by the end of the experiment regardless of the chosen night-time ventilation strategy. The colony count in the air was low throughout the study period. Therefore, the results indicate that the long-term growth on the walls of air ducts is unlikely and the risk of microbial transfer from the air ductworks to room space is low.
... Present results are discussed in the context of the need for humidification to moderate RH levels of 30-60% in buildings 45 ; higher levels are not recommended because of the risks associated with condensation and molds 46 . Figure 2 compares the effect of RH on the different viruses examined in the present analyses by calculating the relative change in infection risk compared with the low RH and low ventilation rates. ...
With a modified version of the Wells-Riley model, we simulated the size distribution and dynamics of five airborne viruses (measles, influenza, SARS-CoV-2, human rhinovirus, and adenovirus) emitted from a speaking person in a typical residential setting over a relative humidity (RH) range of 20–80% and air temperature of 20–25 °C. Besides the size transformation of virus-containing droplets due to evaporation, respiratory absorption, and then removal by gravitational settling, the modified model also considered the removal mechanism by ventilation. The trend and magnitude of RH impact depended on the respiratory virus. For rhinovirus and adenovirus humidifying the indoor air from 20/30 to 50% will be increasing the relative infection risk, however, this relative infection risk increase will be negligible for rhinovirus and weak for adenovirus. Humidification will have a potential benefit in decreasing the infection risk only for influenza when there is a large infection risk decrease for humidifying from 20 to 50%. Regardless of the dry solution composition, humidification will overall increase the infection risk via long-range airborne transmission of SARS-CoV-2. Compared to humidification at a constant ventilation rate, increasing the ventilation rate to moderate levels 0.5 → 2.0 h⁻¹ will have a more beneficial infection risk decrease for all viruses except for influenza. Increasing the ventilation rate from low values of 0.5 h⁻¹ to higher levels of 6 h⁻¹ will have a dominating effect on reducing the infection risk regardless of virus type.
... Zuzana et al. provides a report on the varying ranges of moisture level conditions that allow mold growth, but roughly conclude that the critical level lie between the RH of 75% to 95% [13]. Daranee et al. confirm that as hot and humid climate result in a higher risk for mold growth in the indoors of concrete structures [14], RH control should be maintained throughout the year. ...
An evaluation method for assessing the difference in the relative humidity (RH) control performance of waterproofing material is proposed. For a demonstration of this evaluation method, two waterproofing materials (urethane coating and cementitious waterproofing material) installed with different methods (positive and negative side of concrete structure respectively) are exposed to temperature conditions representing three seasonal conditions: Summer (40 °C), spring/autumn (20 °C) and winter (4 °C). Condensation level changes on the inner side of the waterproofing material installed specimen is measured, and for derive criteria for comparison, three parameters based on the average RH, intercept RH (derived from a linear regression analysis of RH measurement), and maximum relative humidity are derived for each different waterproofing material installed specimen. Based on quality specification for underground concrete structures, the demonstration evaluation establishes provisional standard criteria of below 70% RH, and all three parameters are evaluated to determine whether the tested waterproofing material/method complies to the performance requirement. Additional analysis through linear regression and cumulative probability density graphs are derived to evaluate the RH consistency and range parameters. The evaluation regime demonstrates a quantitative RH analysis method and apparatus, and a newly designed evaluation criteria is used to compare the RH control performance of positive-side installed urethane waterproofing materials and negative-side installed cementitious waterproofing material.
... The mold growth and the conditions for interior comfort can be represented in a psychometric chart (Fig. 8) [20]. Mold growth is influenced by various factors, including temperature, relative humidity, nutrition, and pH. ...
Recently, condensation and mold problems in apartment buildings have been on the rise due to increased insulation and airtightness performance for energy savings. Occupants in residential buildings have suffered property damages due to condensation and mold on built-in furniture, especially in Korean apartment buildings. Generally, condensation and mold growth on built-in furniture were found during summer and winter on the back panels of the furniture and adjacent surfaces of the walls, floor, and ceiling. These problems are related to the weather and indoor room conditions. To solve these problems, it is necessary to investigate the thermal environment around the built-in furniture and in living spaces during summer and winter. The aim of the study was to analyze the thermal environment around the built-in furniture during summer and winter. Through field measurements at apartment buildings that were constructed from 1990 to 2014, the thermal conditions around the built-in furniture were assessed. Results indicate that nine target apartment buildings did not incur condensation during summer, but they suffered from mold. Four apartment buildings, which were constructed after 2004, incurred condensation during winter, but they did not suffer from mold. Based on our results, we have prepared a solution design guide for preventing condensation and mold around built-in furniture.
The occurrence of mould and effect of formaldehyde emission on indoor air pollution has been widely reported. However, the potential effect of mould on formaldehyde emissions from building materials has been rarely examined. In this study, the formaldehyde emission from medium-density fibreboards was monitored in three full-scale unoccupied experimental houses for 24 months. Moulds were infested in two out of the three houses. Different indoor formaldehyde concentrations were observed accordingly. Three different stages of variation in concentrations were observed among the houses. In the first stage, when there was no mould growth in any of the houses, indoor formaldehyde concentrations varied in the same way. In the second stage, a large amount of mould was infested in one of the houses, and its formaldehyde concentration was reduced substantially and exhibited a trend opposite to those of the other two houses. In the third stage, 5% of the medium-density fibreboards were covered with mould in another house, and the difference in formaldehyde concentration compared to that in the house without mould growth was increased after that. The different indoor formaldehyde concentrations due to the presence of mould in these houses indicated the inhibitory effect of mould growth on formaldehyde emissions.
