filtration

A study examined by chemical analysis (without prior culture) bacterial levels in dust collected from hospital air conditioning filters. Gas chromatography-mass spectrometry methods were used to analyse the dust. Concludes that there is potential for the chemical assessment of the microbial content of airborne dust.

States that on using the ELISA inhibition test against Aspergillus fumigatus, the study found that air samples from air conditioned rooms showed inhibition of the serum activity of a highly sensitized patient. Concludes that although an important fraction of aeroplankton particles can be filtered out of air conditioning systems, airborne allergens can nevertheless pass both coarse and fine filters.

The effectiveness of in-room air filtration systems was experimentally evaluated, specifically portable air filters (PAFs) and ceiling-mounted air filters, in conjunction with dilution ventilation, in order to control TB exposure in high-risk environments. A test aerosol was continuously generated and released into a full-sized room. Time-averaged airborne particle concentrations were measured at several points. The effectiveness was determined by a comparison of particle concentrations with and without device operation. Increasing rate of air flow did not always increase effectiveness.

The developing trend that Building Regulations in the future will be applied to buildings in use rather than to their design intent on paper has many important implications. It will lead to pressure testing of new buildings to ensure air tightness, low energy bills and the associated absence of draughts. Importantly, it means that for the first time, the ventilation air will enter the building through the air inlet ductwork. This offers the designers the opportunity to control the indoor environment to create refreshing comfortable climate while retaining low energy use.

Much publicity has been given to the potential health risks posed by buildings, particularly those with mechanical ventilation or air conditioning. There have been concerns over the possible effects of the vocs given off by the furnishings and finishes, of fungal spores shed from dirty ducting, of legionella distributed by wet cooling towers, of insufficient ventilation air, etc., etc. The list of concerns is a long one. But what about the effects on the building occupants of the air brought in from outside, the so-called 'fresh air'?

Forced air furnaces are a common Canadian heating system. Traditionally, filters placed in the circulating air ductwork were designed to protect the furnace and fans . Over the last several years, there has been increased emphasis on improving the filtration efficiency with the goal of reducing occupant exposure to respirable particulate. This research project rotated several filters through six houses in southern Ontario during the heating season.

The provision of a healthy and satisfactorily clean indoor environment requires that consideration be given to a range of issues, such as the type of indoor environment, indoor and outdoor sources, indoor activity and others. The selection of relevant measures to achieve the required indoor air quality (IAQ) depends on knowledge and understanding of the mechanisms and parameters affecting the concentration levels indoors.

We studied the effect of ventilation and air filtration systems on indoor air quality in a children's day-care center in Finland. Ambient air nitrogen oxides (NO, N02) and particles (TSP, PM10) were simultaneously measured outdoors and indoors with automatic nitrogen oxide analyzers and dust monitoring. Without filtration nitrogen oxides and particulate matter generated by nearby motor traffic penetrated readily indoors. With chemical filtration 50-70% of nitrogen oxides could be removed. Mechanical ventilation and filtration also reduced indoor particle levels.