English

Measurements were carried out in a test chamber with displacement ventilation to know the vertical distribution of airborne particles generated by two human subjects having an activity representative of that of people working in an office. Particle concentration was observed as increasing with height. A threshold size of particles was found at 5 to 10 microns above which the displacement effect of particles by air flow started to decline. Negative concentration gradients were observed for large particles at the lowest ventilation rate, when the air flow does not displace them.

Resistance of louvers to the penetration of snow is a main parameter in Nordic countries. The study presents an experiment on 10 louvers tested in situ. The snow has been collected in bag filters and pressure drop variation was the chosen criteria for ranking the louvers.

On 75 air outlets of HVAC systems from 12 participating companies, fungal contamination was measured and compared to the incoming fresh air. For one of them with a significantly high level of fungi, dominated by one penicillium species, regular checks on a period of 14 months have been realised. The study concludes that this kind of measurement can be used as an indicator of the HVAC system hygienic condition.

To minimise emissions from ducts, it is necessary to manufacture with low emission lubricants or with lubricants that leave only minor amount of residues on the surface. In this study the lubrication, evaporation and odour emission properties of fourteen lubricants were studied and differences are high ligthted showing the importance to select them properly.

This paper studies the overall accuracy and comparability of both trained and untrained panels in order to determine the required size of the untrained panel, and to determine the limit value (mean vote) corresponding to an acceptable air quality. In the results, it is proposed to use an untrained panel of 15 persons. The risk connected with the use of such a small, untrained panel was calculated to be 10 % and is equivalent to trained panel.

The study examined emissions from dust collected on 2 stages ventilation filters in winter in Helsinki or in its outskirts. The filters contained a lot of fresh particles due to traffic, combustion, and power production. The carbon content was highest in the dust, which was collected from a pre-filter. In previous studies, the intensity of odors from filters was found to be strongest in the winter.

The study compares on 30 ventilation systems an hygienic factor determined from conditions at air intake (including moisture before and after drainage, porosity and contamination) and microbiological analysis of air. The aim is to identify ventilation systems potential risk for indoor air contamination.The study has shown a clear relationship between the microbiologic and the hygienic conditions; i.e. dry and clean intakes are less likely to be microbially contaminated. The method seems to identify potential problems, which could be confirmed by a microbiological study.

This study presents a literature review on oil residues on HVAC components. A sampling of oil residues by filter contact method and analysis by infrared spectroscopy method have been developped. Amounts of oil residues on surfaces of components varied a lot (<10 mg/m to 700 mg/m) but were significantly correlated to odour intensity. Cleaning of oil residues from the duct surfaces with typical cleaning methods is very difficult and it is better to deliver from the manufacturer components free of oil residues.

The study monitored two similar ventilation systems with fine filters during a few months, one operating continuously, one only during day time. Air, surface and filter material samples were taken to evaluate the extent of microbial contamination with viable fungi and bacteria. Filter and air of the permanent system,with higher relative humidity, were less contaminated by microbes and the contamination was more evenly spread in the filter.

A two-years old filter was placed in a ventilation system recirculating the air in an experimental space. Via glass tubes air was extracted to an adjacent room to allow a panel to evaluate the sensory load after facial exposure, without entering the space. The sensory pollution load of the filter determined from full exposure was approximately 7 times lower than when determined after facial exposure. Even though, used filters may still be important sources of indoor air pollution.