Exhaust systems for dust and smoke - design optimization by CFD and realization

2 examples of extract systems are presented in this paper : the first one concerns dust removal in a public waste plant and the second smoke separation in a smoker/non-smoker zone with no visual impact (i.e. no walls).Thanks to the CFD simulation, proper exhaust systems for dust and smoke have been successfully designed and optimised for each case with simulation results. The proposed solutions were then realized and with few minor modifications led to excellent working conditions on the one hand and excellent smoke caption on the other hand.

Total dust exposure and size distribution of air borne particles in day-care centres, schools and offices

Values for total dust concentration in indoor air in day-care centres, offices and schools with no reported problems are measured. These are: day-care centres 41 14 g/m3, offices 16 5 g/m3, schools 20 10 g/m3. In parallel the particle size distribution in six interval from 0.3 m - >20 m are reported. No seasonal variation in total dust concentration could be seen. Sudden increase in number of the particles in the smallest intervals are found at night for some systems when they are shut down or working on reduced speed.

Measurement, explanation and prevention of particle deposition near ceiling induction outlets

The deposit of particles on ceilings close to ventilation outlets is mainly caused by the features of mixed ventilation, turbulence and induction. This study aims at solving that annoying problem of particle deposition, for the ventilation industry. The development of a clean outlet is eased thanks to a new experimental approach using an optical technique (in so far as the experimental technique and the CFD calculations are too inefficient).

The field comparison of three measuring techniques for evaluation of the surface dust level in ventilation ducts

Three measuring techniques have been compared for evaluation of the surface duct level in ventilation ducts : vacuum test, gravimetric tape method, optical tape method. Measurements have been operated in 13 recent buildings in Helsinki using the three methods. The vacuum test gives similar values to the gravimetric tape method when air ducts show no residual oil from their manufacturing (average values 1.1 and 1.2 g/m2). With residual oil, vacuum test gives higher dust levels than gravimetric tape method. The optical tape method is the most easy to use on site.

Volatile organic compounds, respirable dust, and personal factors related to prevalence and incidence of sick building syndrome in primary schools.

This study explored the possible connections between the incidence and prevalence of sick building syndrome (SBS), indoor exposures, and personal factors. This was accomplished by a four year longitudinal study of workers in six primary schools. The mean concentration of Carbon Dioxide exceeded the recommended value of 0.08 microlitres/l (800 ppm) in all schools, which suggested a poor outdoor air supply. Indoor levels of volatile hydrocarbon (VOC) was increased at high room temperatures.

Effectiveness of duct cleaning methods applied in new air ducts.

This study was based upon a laboratory comparison of two air duct cleaning methods, mechanical brushing and compressed air cleaning. These methods were compared in three types of round air ducts: a metal duct without oil residual, a metal duct with oil residual, and a plastic duct. The level of cleanliness was estimated both by using the vacuum test method and visually, and the time each method took was recorded. Two rotating speeds of the brush and various brush materials were used.

Trichothecene mycotoxins in the dust of ventilation systems in office buildings.

Suggests dust sample analysis as a rapid technique for detecting the presence of mycotoxins in the dust of ventilation systems.

House-dust mite allergen concentrations (Der f 1) and mould spores in apartment bedrooms before and after installation of insulated windows and central heating systems.

Attempts to determine the influence of the installation of highly insulated windows and central heating systems on indoor climate, and mite-allergen (Der f 1) and mould spore concentrations. A before and after study was carried out on 98 apartment bedrooms, with measurements taken of air exchange rate, temperature and humidity. A lifestyle and housing conditions questionnaire was undertaken by the occupants and dust on carpets and mattresses was analysed for mould spores and Der f 1.

Monitoring of bacterial sugars and hydroxy fatty acids in dust from air conditioners by gas chromatography-mass spectrometry.

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.

Exposure to varying levels of contaminants and symptoms among workers in two office buildings.

The outdoor air supply was manipulated over a period of six week in two mechanically ventilated offices in Montreal, and symptoms and environmental parameters noted. Higher dust and higher nitrogen dioxide concentrations led to eye symptoms reports. Higher TVOCs were associated with mucosal symptoms. Higher dust levels were associated with systemic symptoms.