Initial studies of oxidation processes on filter surfaces and their impact on perceived air quality
- 1 February 2006
- journal article
- Published by Hindawi Limited in Indoor Air
- Vol. 16 (1) , 56-64
- https://doi.org/10.1111/j.1600-0668.2005.00401.x
Abstract
Used filters can be a strong sensory pollutant source. Oxidation processes, especially those initiated by ozone, may contribute to the pollutants emitted from such filters. In the present study, ozone was added to the airstream passing through used ventilation filters. Two flow rates were examined. While the upstream ozone concentration was approximately 75 ppb, the concentrations downstream of the filter were initially 35-50% lower. However, within an hour downstream concentrations were only 5-10% lower than those upstream. These filter samples were then placed for 48 h in nitrogen, ambient air containing less than 5 ppb ozone, or ambient air at an elevated temperature. This resulted in partial regeneration of the ozone removal capability of the filter. In analogous experiments, lower ozone removal occurred when the filter samples were first ventilated for 24 h with ozone-free air before making the measurements. Samples from a new filter removed <10% of the ozone in the airstream, and removal remained relatively constant over time. In companion studies, human subjects assessed the air passing through various used filter samples. In the initial evaluation each of the four filter samples, taken from the same filter and ventilated for 24 h, were assessed to be equivalent. The next evaluation was immediately after the samples had been kept for 24 h in either nitrogen, air, air at an elevated temperature or ozone. The nitrogen-treated filter was assessed to be best, while the ozone-treated filter was assessed to be the worst. The final evaluation occurred after ambient air had passed through the 'treated' filters for 2 h. All such ventilated filters were assessed to be more acceptable than immediately after the 24-h treatments; the ozonized and air-treated filters were the most polluting of the four. Practical Implications The present paper supports previous findings that loaded ventilation filters can be significant sources of sensory pollution. Replacing a loaded filter with a new filter temporarily removes this source of pollution. However, the present study does not provide an answer to how frequently changes are needed under different conditions. The results indicate that in cases of intermittent operation of ventilation systems, the airflow through the polluted filters should be restarted in sufficient time prior to occupancy to purge odorous pollutants that have accumulated on the filter surface. Removal of ozone upstream of the particle filters may further improve perceived air quality in the space downstream of the filter bank. Future efforts related to the development and application of low-polluting filtration systems are warranted.Keywords
This publication has 12 references indexed in Scilit:
- Ventilation filters and indoor air quality: a review of research from the International Centre for Indoor Environment and EnergyIndoor Air, 2004
- Chemical reactions among indoor pollutants: what we've learned in the new millenniumIndoor Air, 2004
- Indoor/outdoor connections exemplified by processes that depend on an organic compound's saturation vapor pressureAtmospheric Environment, 2003
- Reactions of Ozone on Ventilation FiltersIndoor and Built Environment, 2003
- Adsorption and desorption of selected VOCs in dust collected on air filtersAtmospheric Environment, 2001
- New Indoor Carpet as an Adsorptive Reservoir for Volatile Organic CompoundsEnvironmental Science & Technology, 2000
- Potential reactions among indoor pollutantsAtmospheric Environment, 1997
- Sensory Pollution and Microbial Contamination of Ventilation FiltersIndoor Air, 1996
- Increase in Perceived Odor Emissions with Loading of Ventilation FiltersIndoor Air, 1994
- Air pollution sources in offices and assembly halls, quantified by the olf unitEnergy and Buildings, 1988