Effects of room furnishings and air speed on particle deposition rates indoors

Thatcher, Tracy L.; Lai, Alvin C.K.; Moreno-Jackson, Rosa; Sextro, R.G.; Nazaroff, William W.

doi:10.1016/s1352-2310(02)00157-7

Cited by 341 publications

(309 citation statements)

References 16 publications

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“…In this study, the used deposition velocity was a combination of measurements and theoretical assumption from studies (Xu et al 1994, Thatcher et al 2002, Lai and Nazaroff 2000. The penetration factor was also calculated with other deposition velocities measured in similar chambers.…”

Section: Discussionmentioning

confidence: 99%

“…Thus, there is considerable uncertainty in the typical values of deposition velocities for buildings. In this study the deposition velocity used was adapted from results reported in Xu et al (1994), Thatcher et al (2002), and is extrapolated with theoretical predictions of Lai and Nazaroff (2000), the same deposition velocity is used also in Fisk et al (2002). Deposition velocity, Equation (4), used here is based on a combination of measured data from full size rooms and extrapolations consistent with theoretical predictions, and it is valid for particle diameters between 0.3 -8 µm, Figure 2. ( ) 6 58 .…”

Section: Penetration Factormentioning

confidence: 99%

“…Also this study was excluded as it most probably overestimates the deposition velocity in laboratory conditions. Fogh et al 1997 5 Thatcher et al 2002 The air flow to chamber 2 (CH2) and from chamber 1 (CH1) were defined by measuring air flow velocities. The penetration factor for inert particles was calculated from the values when both chambers had reached steady state.…”

Section: E-06mentioning

confidence: 99%

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Fungal spore transport through a building structure

Airaksinen¹,

Kurnitski²,

Pasanen

et al. 2004

Indoor Air

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The study carried out laboratory measurements with a full-scale timber frame structure to determine penetration of inert particles with size distribution from 0.6 to 4 µm and spores of Penicillium and Cladosporium through the structure. Pressure difference over and air leakage through the structure were varied. Measurements at moderate pressure differences resulted in the penetration factors within the range of 0.05 to 0.2 for inert particles, and indicated also the penetration of fungal spores through the structure. The measurements showed that the penetration was highly dependent on pressure difference over the structure but not on holes in surface boards of the structure. The results show that surface contacts between the frames and mineral wool may have a significant effect on penetration. The penetration was approximately constant within particle size rage of 0.6-2.5 µm, but particles with diameter of 4.0 µm did not penetrate through the structure at all even at a higher-pressure difference of 20 Pa, except in the case of direct flow-path through the structure. Results have important consequences for practical design showing that penetration of fungal spores through the building envelope is difficult to prevent by sealing. The only effective way to prevent penetration seems to be balancing or pressurizing the building. In cold climates, moisture condensation risk should be taken into account if pressure is higher indoors than outdoors. Determined penetration factors were highly dependent on the pressure difference. Mechanical exhaust ventilation needs a special consideration as de-pressurizing the building may cause health risk if there is hazardous contamination in the building envelope exists. PRACTICAL IMPLICATIONSMeasurements at moderate pressure differences allowed determining penetration factors within the range of 0.05 to 0.2 for inert particles in a size range of 0.6-2.5 µm and indicative results with fungal spores confirmed the penetration through the wooden floor structure. Both measurements showed that the penetration was highly dependent on pressure difference and not dependent on holes in surface boards of the structure. The results are likely to show that surface contacts of mineral wool with other building elements may have an important role on the penetration.

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Section: Discussionmentioning

confidence: 99%

Section: Penetration Factormentioning

confidence: 99%

Section: E-06mentioning

confidence: 99%

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Fungal spore transport through a building structure

Airaksinen¹,

Kurnitski²,

Pasanen

et al. 2004

Indoor Air

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“…Although particle deposition onto indoor surfaces have been studied extensively (Offermann et al 1985;Thatcher et al 2002;Thatcher et al 2003;Vette et al 2001), there are limited relevant experimental data (Ott et al 2007) or theoretical models to provide the exact value of deposition coefficient inside vehicles. Airflow speed and surface area are two main factors determining the deposition coefficient (Thatcher et al 2002), and these factors are quite different between the in-cabin and the indoor microenvironments. In-cabin air exchange rates, 1.9-48.5 h −1 (Ott et al 2007), are much greater than those found in typical indoor environments which are usually on the order of 0.5 h −1 (Murray and Burmaster 1995).…”

Section: Deposition Coefficient (␤)mentioning

confidence: 99%

Quantitative Analysis of the Parameters Affecting In-Cabin to On-Roadway (I/O) Ultrafine Particle Concentration Ratios

Zhu

2009

Aerosol Science and Technology

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A mass-balance indoor particle dynamic model was adopted and modified to investigate how on-roadway ultrafine particle (UFP, diameter < 100 nm) concentrations and vehicle ventilation settings affect UFP levels inside vehicles. The model was first parameterized focusing on a mechanistic, simulation-based interpretation of in-cabin data reported in Zhu et al. Under condition (3), the effects of penetration factor, deposition coefficient, and vehicle speed were comparable. The modeled I/O ratio was inversely proportional to the airflow rate from mechanical ventilation in the whole range (0-360 m 3 h −1 ) with 10-20% influence depending on the particle size.

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“…This increased decay rate of particles in the chamber could have been caused by several factors, including underestimation of particle size by the APS, electro- static deposition in the chamber, or impaction on fan or other surfaces (Thatcher et al 2002). The latter two loss mechanisms were reduced to the extent possible.…”

Section: Aerosol Particle Size and Concentration Decaymentioning

confidence: 99%

Development of an Aerosol System for Uniformly Depositing Bacillus Anthracis Spore Particles on Surfaces

Baron

Estill

Deye

et al. 2008

Aerosol Science and Technology

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After the anthrax incidents in October 2001, several techniques used for sampling surfaces for biological agents were found to be inadequately validated, especially at low surface loadings. Therefore a test chamber was developed to produce sample sets having targeted surface concentrations of dry biological agent simulant. Dry spore aerosols were initially dispersed into the chamber at relatively high air concentrations, and monitored in real time. The concentration decay (due to stirred settling and dilution) was measured and when the targeted air concentration was reached, the sampling surfaces were uncovered and exposed to the settling particles until >99% of the particles had settled. Multiple agar plates were used to estimate the true colony-forming-unit (CFU) surface concentration. The uniformity of surface loadings was limited by random deposition of small numbers of particles on the surfaces (Poisson distribution) and was characterized by how much greater the observed variability was than that predicted by Poisson statistics. The flow-enhanced powder mixture appeared to affect the spores' ability to grow on the agar medium. Three ways of analyzing the agar plates were used to evaluate the effect of spore coatings on viability and to differentiate between number of spore-containing particles and the number of spores. The presence of spore agglomerates resuspended by various sample handling activities in the chamber further increased the variability of deposited particles. Based on estimated airborne particle concentration, it was possible to predict mean agar plate concentrations within narrow confidence intervals (CI) at low (4.8 CFU, 95% CI 3.5-6.4), medium (20 CFU, 95% CI 17-23), and high (160 CFU, 95% CI 140-190) concentrations.

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Effects of room furnishings and air speed on particle deposition rates indoors

Cited by 341 publications

References 16 publications

Fungal spore transport through a building structure

Fungal spore transport through a building structure

Quantitative Analysis of the Parameters Affecting In-Cabin to On-Roadway (I/O) Ultrafine Particle Concentration Ratios

Development of an Aerosol System for Uniformly Depositing Bacillus Anthracis Spore Particles on Surfaces

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