filtration

Indoor Air quality (IAQ) of dwellings is the result of several sources and processes, and the impact of ventilation system is the one amongst many others. Definition and metrics of IAQ are several and we choose in this study to focus on airborne particle levels. Our question was: How the filtration of supply air impacts particle levels in indoor air?  

Activated carbon filters have been used forpurification of air and water in industrialapplications. However these technologies have notbeen applied to the non-industrial builtenvironment in general and there is no standard toquantify or to classify the performance of thesesystems for in-duct mechanical systemapplication.

The deposition rates of particles in a town-house with a forced air circulation and in-duct filters have been calculated for that study. It appears that the use of central forced-air fan along with in-duct filters allows the reduction of particle concentration. And it is more effective than reducing ventilation by closing windows or making homes more insulated.

For that study an experiment was conducted during 2 months, in a call center : each week 26 operators returned questionnaires recording their environmental perceptions and sick building syndrome symptoms. In parallel, the recording of their average talk-time was monitored every 30 minutes.The results of that study confirm that increasing outdoor air supply rates and replacing used filters with new ones has a positive effect on health, comfort and productivity of workers.

In this study, serial environmental measurements in 12 large buildings in Taiwan have been made to control the air exchange efficiency on the indoor microbial contamination. High levels of airborne microbes seem to be more easily observed in buildings equipped with fan coil unit system than with air handling unit system.
Adequate filtration of fresh air intake should be imperative to control effectively microbial contaminations of outdoor origin.

In Hong Kong, design and construction of new operating rooms and upgrading of older ones have been based on the UK Health Building Notes. In a case study, field measurements showed that the airflow and some design features did not tally with the specifed requirements.
As the risk of contamination in an operating room can be minimized through appropriate filtration and air distribution scheme, a CFD analysis was carried out with the simulation of the temperature distribution, airflow pattern and the contaminant dispersion.

Electret media or "charged" media are electrostatically charged materials that attract, like magnets do, microscopic charged or uncharged particulates. Those media are not the same in structure, stability, distribution of charge and size of their internal electric fields. Charge and structure together determine an electret media performance. In this paper the results of different filter media put to the tests are presented.

An optimal placement of outside air intakes is important for a good IAQ protection. A proper intake placement can also reduce the need for filtration, and reduce re-entrainment of chemical emissions.

Airborne particle concentrations of 20 nm to 10 µm particles were studied in two similar classrooms in a school. One classroom was ventilated by mixing ventilation with supply air filtration and one by displacement ventilation without supply air filtratio

This paper is a review of almost two decades work on pollution sources in ventilation systems. There is a special emphasis on ventilation filters with reference to the work of other researchers. A view into future research and developement with engineering solutions is also presented.