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Influence of mechanical ventilation system on indoor carbon dioxide and particulate matter concentration.

ABSTRACT: Common ventilation strategies may fail to maintain indoor air quality when atmosphere is heavily polluted by particulate matter. This paper evaluates the performances of common constant air volume (CAV) system and variable air volume (VAV) system when carbon dioxide and particles are significantly present in outdoor environment. Major system parameters including filter efficiency, occupancy number, ventilation air rate, and outdoor particle concentration are thoroughly examined. Firstly, a full-scale chamber experiment is performed to investigate the dynamics of CO2 and airborne particles under steady and non-steady scenarios. The result is further validated with a previously-developed state-space model. Secondly, an exhaustive case study is conducted using an established mathematical model. In order to reduce CO2 concentration, both CAV and CO2-based demand-controlled VAV may cause an undesirable increase in particle concentration when outdoor air is heavily polluted by particles. This dilemma requires further studies on the optimization of ventilation schemes.

SUBMITTER: Yu CKH

PROVIDER: S-EPMC7126795 | biostudies-literature | 2014 Jun

REPOSITORIES: biostudies-literature

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Influence of mechanical ventilation system on indoor carbon dioxide and particulate matter concentration.

Yu Conson K H CKH Li Min M Chan Vincent V Lai Alvin C K ACK

Building and environment 20140313

Common ventilation strategies may fail to maintain indoor air quality when atmosphere is heavily polluted by particulate matter. This paper evaluates the performances of common constant air volume (CAV) system and variable air volume (VAV) system when carbon dioxide and particles are significantly present in outdoor environment. Major system parameters including filter efficiency, occupancy number, ventilation air rate, and outdoor particle concentration are thoroughly examined. Firstly, a full- ...[more]

PMID: 32288026

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Project description:People generally spend more time indoors than outdoors resulting in a higher proportion of exposure to particulate matter (PM) occurring indoors. Consequently, indoor PM levels, in contrast to outdoor PM levels, may have a stronger relationship with lung function. To test this hypothesis, indoor and outdoor PM2.5 and fungal spore data were simultaneously collected from the homes of forty-four asthmatic children aged 10-16?years. An optical absorption technique was utilized on the collected PM2.5 mass to obtain concentrations of black carbon (BC) and ultraviolet light absorbing particulate matter, (UVPM; a marker of light absorbing PM2.5 emitted from smoldering organics). Enrolled children completed spirometry after environmental measurements were made. Given the high correlation between PM2.5, BC, and UVPM, principal component analysis was used to obtain uncorrelated summaries of the measured PM. Separate linear mixed-effect models were developed to estimate the association between principal components of the PM variables and spirometry values, as well as the uncorrelated original PM variables and spirometry values. A one-unit increase in the first principal component variable representing indoor PM (predominantly composed of UVPM and PM2.5) was associated with 4.1% decrease (99% CI?=?-6.9, -1.4) in FEV1/FVC ratio. 11.3??g/m3 increase in indoor UVPM was associated with 6.4% and 14.7% decrease (99% CI?=?-10.4, -2.4 and 99% CI?=?-26.3, -2.9, respectively) in percent predicted FEV1/FVC ratio and FEF25-75 respectively. Additionally, 17.7??g/m3 increase in indoor PM2.5 was associated with 6.1% and 12.9% decrease (99% CI?=?-10.2, -1.9 and 99% CI?=?-24.9, -1.0, respectively) in percent predicted FEV1/FVC ratio and FEF25-75, respectively. Outdoor PM, indoor BC, and indoor fungal spores were not significantly associated with lung function. The results indicate that indoor PM is more strongly associated with lung function in children with asthma as compared with outdoor PM.

Project description:Background:Tidal hyperinflation can still occur with mechanical ventilation using low tidal volume (LVT) (6?mL/kg predicted body weight (PBW)) in acute respiratory distress syndrome (ARDS), despite a well-demonstrated reduction in mortality. Methods:Retrospective chart review from August 2012 to October 2014. Inclusion: Age >18years, PaO2/FiO2<200 with bilateral pulmonary infiltrates, absent heart failure, and ultra-protective mechanical ventilation (UPMV) defined as tidal volume (VT) <6?mL/kg PBW. Exclusion: UPMV use for <24?h. Demographics, admission Acute Physiology and Chronic Health Evaluation II (APACHE II) scores, arterial blood gas, serum bicarbonate, ventilator parameters for pre-, during, and post-UPMV periods including modes, VT, peak inspiratory pressure (PIP), plateau pressure (Pplat), driving pressure, etc. were gathered. We compared lab and ventilator data for pre-, during, and post-UPMV periods. Results:Fifteen patients (male:female?=?7:8, age 42.13?±?11.29 years) satisfied criteria, APACHEII 20.6?±?7.1, mean days in intensive care unit and hospitalization were 18.5?±?8.85 and 20.81?±?9.78 days, 9 (60%) received paralysis and 7 (46.67%) required inotropes. Eleven patients had echocardiogram, 7 (63.64%) demonstrated right ventricular volume or pressure overload. Eleven patients (73.33%) survived. During-UPMV, VT ranged 2-5?mL/kg PBW(3.99?±?0.73), the arterial partial pressure of carbon dioxide (PaCO2) was higher than pre-UPMV values (84.81?±?18.95 cmH2O vs. 69.16?±?33.09 cmH2O), but pH was comparable and none received extracorporeal carbon dioxide removal (ECCO2-R). The positive end-expiratory pressure (14.18?±?7.56 vs. 12.31?±?6.84 cmH2O), PIP (38.21?±?12.89 vs. 32.59?±?9.88), and mean airway pressures (19.98?±?7.61 vs. 17.48?±?6.7?cm H2O) were higher during UPMV, but Pplat and PaO2/FiO2 were comparable during- and pre-UPMV. Driving pressure was observed to be higher in those who died than who survived (24.18?±?12.36 vs. 13.42?±?3.25). Conclusion:UPMV alone may be a safe alternative option for ARDS patients in centers without ECCO2-R.

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Influence of mechanical ventilation system on indoor carbon dioxide and particulate matter concentration.

Publications

Influence of mechanical ventilation system on indoor carbon dioxide and particulate matter concentration.

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