filter

The fine filter (EU7) was included in the ventilation system which operated at full capacity only during working days. The first three months the filter was located in the ventilation system of the office building and it was later moved for one month period into the laboratory chamber. The aim of the study was to investigate whether particles or microbes are released from the filter during the turn off and start up of the fan. The released particle (size range of 0.3 m) concentration was below 10 #/dm 3 in normal field conditions.

The needle heat exchanger (acts as a pre filter EU3) was installed in front of the glass fiber used as a fine filter (EU7) in the supply air chamber. Thus, the temperature of the supply air increased and the relative humidity of the fine filter next to the heating unit decreased. The aim of this study was to examine how the installation of the needle heat exchanger effects on the microbial growth and release in the fine filter. The relative humidity of the fine filter in the supply air unit fell below 70 % during different seasons.

Adsorbant filters are used to reduce odours and gas concentrations in air. They are also used in industry as well as in the commercial environment to treat ventilation air in buildings and motor vehicle conditioning systems. The article discusses methods to determine their performance.

The survival of bacterial and mould spores in new and used air filter media is explored. Samples of different media were challenged with specific microbial aerosols in a filtration test unit, and the viability of the microorganisms collected in the filter media examined. In five days there was no noticeable decrease or increase in the viability, nor did relative humidity have an influence.

In seven hospitals in the eastern United States air filters of various types, selected by discoloration, were collected from the primary and secondary filter banks of the HVAC systems. The samples were then examined with direct microscopy for fungal colonization. Results showed that filters from five of the hospitals were colonized with fungi. Several of the species had not previously been reported to colonize air filters.

Describes how new and used cellulosic air filters for HVAC systems including those treated with antimicrobials were suspended in vessels with a range of relative humidities, and containing non-sterile potting soil to stimulate fungal growth. Prior to suspension in the chambers most filters yielded fungi, but only two of 14 non-treated filters demonstrated fungal colonization following use in HVAC systems. Antimicrobial-treated filters, in particular a phosphated amine complex showed a lot less fungal colonization than nontreated filters.

The study aimed to evaluate the emission of volatile organic compounds from air filters. In the first part of the project, carbonyl compounds were measured by reacting them with 2,4-dinitrophenylhydrazine. HPLC and UV detection were used for the analysis. Laboratory experiments used pieces of used and unused HVAC filters, incubated in test chambers. The used filters used in the experiments were from a filter bank of a large HVAC system in the middle of Berlin, Germany.

A children's day care centre in Finland was the site of a study on the effect of ventilation and air filtration systems on indoor air quality. Indoor and outdoor concentrations of NO, NO2, TSP and PM10 were measured using automatic nitrogen oxide analysers and dust monitoring. Nitrogen oxides and particulate matter from traffic penetrated easily in the absence of filters.50%-70% of nitrogen oxides were excluded with chemical filtration. At holidays and weekends, the particle levels fell less than 10% of the outdoor level, rising to 25% on weekdays.

To ensure good indoor air quality in buildings, filters are installed in the ventilation ducts. These filters cause a pressure drop in the ducts, so that increased power to the ventilation fans is required to maintain the flow of fresh air. To reduce this problem, the Norwegian company, Interfil, developed a new energy efficient filter in 1995. This filter has been carefully tested in recent years. The test results show that, compared to ordinary filters, the new filters could reduce fan power by about 10%, while maintaining indoor air quality.