Experimental measurement of bioaerosol concentrations and containment in long-term care environments

Relationship Between Airborne Fungi Presence and the Position of the High Efficiency Particulate Air Filter in the Heating, Ventilation, and Air Conditioning System

“…UNE 171340 (2020) establishes the thresholds of relative humidity between 40% and 60% for all controlled environment rooms. This is in line with the review by Mousavi et al (2019) which concludes that relative humidity between 40% and 60% is the most unfavorable condition for the survival of microorganisms. However, in this study, relative humidity was outside the multivariable model, because we obtained no significant differences in relative humidity (between rooms) and the absence and presence of fungi.…”

Holistic understanding of ventilation rate in occupational health risk control

“…Note that Equation (2) is a simplified form of Equation (1) for spaces with 100% outdoor air ($$\alpha \; = {\mathrm{\;}}1$$) or 100% contaminant removal efficiency ($$\eta \; = {\mathrm{\;}}1$$). While it is generally expected that contaminant levels would proportionately decrease when the $$AC{H_{{\mathrm{clean}}}}$$ value increases, previous studies show less than expected contaminant concentration decreases due to imperfect air mixing 18 . The author believes that interruption of contaminant removal mechanisms (e.g., surface deposition, particle gravitational settling) due to airflow turbulence at higher air exchange rates possibly explains this finding.…”

“…There is a growing body of evidence for the value of aerosol‐based tracing technology with qPCR quantification to assess ventilation efficacy 70,71 . For example, one study conducted DNA‐tagged bioaerosol sampling and testing in a long‐term care facility to assess the dispersal of test particles and the impact of ventilation on test particle concentrations 18 . The results indicated that increasing the ventilation rate in the room in which the test particles were released did little to prevent particle dispersal outside the room, although the time needed to reduce the within‐room particle concentration by 99% was reduced to about half an hour.…”

“…While it is generally expected that contaminant levels would proportionately decrease when the ACH clean value increases, previous studies show less than expected contaminant concentration decreases due to imperfect air mixing. 18 The author believes that interruption of contaminant removal mechanisms (e.g., surface deposition, particle gravitational settling) due to airflow turbulence at higher air exchange rates possibly explains this finding. Similarly, Keil further constructed a simplified tool for the estimation of the ventilation rate using concentration decay data fitting the well-mixed room model, though other sophisticated models (such as the nonsteady state method using linear regression or ordinary differential equation models) are also available to conduct refined ventilation assessments in spaces where occupancy varies over time.…”

Informing Building Strategies to Reduce Infectious Aerosol Transmission Risk by Integrating DNA Aerosol Tracers with Quantitative Microbial Risk Assessment

“…We propose a method for combining airborne pathogen transmission risk modeling and physical tracer measurements for modeling the risk reduction that results from infectious aerosol exposure mitigation measures. This is accomplished by integrating quantitative microbial risk assessment (QMRA) − with aerosol concentrations of synthetic DNA tracers collected in buildings. − …”