filter

Highly energy efficient buildings such as ones built to the Passive House standard, require a very airtight building envelope and the installation of a mechanical ventilation with heat recovery (MVHR). MVHR systems incorporate ambient air filters, which reduce the introduction of particulate matter (PM) from outdoor sources into the dwelling. However, indoor PM sources, e.g. cooking, can also contribute substantially to occupants’ exposure and need to be accounted for when designing ventilation or deriving recommendations for filter classes. 

This study is designed to investigate the particulate matter removal efficiency of domestic air cleaner products and seeks to compare the particulate matter removal efficiency in a laboratory with that in real life. 

In the first phase of the current project, the ventilation rates of occupied houses in the northern region of Japan were investigated from 2001 to 2005. It was revealed that, despite installing mechanical ventilation system, low ventilation rate was found in many houses. The causes were believed attributing to lack of cleaning of grills, filters and insect protection meshes. The second phase of the project was to investigate the causes and resolve the problems. This project was started in 2005 and 12 houses installed with mechanical ventilation system were investigated.

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.

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 experiment was performed to determine whether the sensory pollution emitted from a bagfilter that had been used for 3 months in a suburban area in Denmark was influenced bydifferent ways of operating the air-handling unit (AHU). Samples of the used filter were preconditioned to simulate three operating conditions: (1) switched off overnight; (2) airflowreduced to 10% overnight; and (3) continuous 100% operation. Outside air passed through thesamples and the acceptability of the air after the filter was assessed by a panel of subjects.

A 2 × 2 replicated field intervention experiment was conducted in a call-centre providing a national public telephone directory service: outdoor air supply rate was adjusted to be 8 or 80% of the total airflow of 430 l/s (3.5 h-1); and the supply air filt

Ozone concentrations were monitored up- and downstream of used filter samples at airflowsof 1.0 and 0.2 l s-1. The ozone concentration in the air upstream of the filters was ~75 ppb,while the concentration downstream of the filter was initially ~35% lower at 1 l s-1 and ~55%lower at 0.2 l s- 1. Within an hour the removal efficiency had decreased to roughly 5% at1 l s- 1 and 10% at 0.2 l s- 1. These filter samples were then placed in either nitrogen or ambientair for 48 h. Afterwards it was found that there was partial regeneration of the filters ozoneremoval capabilities.

This article analyses and comments 5 papers presented at Indoor Air 2002 Conference (see Airbase records 14454, 14455, 14539, 14695 and 14697) about indoor air quality and filters, from the point of view of filter changing frequency.