particle

An efficient ventilation system is characterised by a well-organised and turbulence-controlled airstream that rapidly corrects disturbances in air quality and thermal comfort in the ventilated space.Air supply and exhaust conditions are investigated here in order to find stable flow conditions andan efficient elimination of both gas and solid phase contaminants. Heat and thermal comfortrequirements are also included.

The Netherlands Agency for Energy and the Environment(NOVEM) is conducting a program for the implementation of Low Temperature Heating (LTH) systems in buildings. The primary goal is to enable the use of Low Talued Energy as a heating source. Major savings in enery consumption can be realised by fully utilising the potential of Low Valued Enery. Besides the argument of savings in energy supply, there are additiond benefits in the fields of. Indoor Air Quality (particles, mites, lower air temperature, annoyance and dust);.

The report describes measurements of the deposition of large particles from a small scale wind tunnel model of a chemical warehouse fire plume. A common feature of such fires is the discharge of relatively large particles with falling speeds of the order of m s- 1, partly generated by mechanical damage, which can fall out of the fire plume in a different pattern to that of the gases and fine particles. These large particles may also contain toxic components, so it is desirable to know their fallout pattern.

Determination of the distribution of contaminant particles within zones becomes of great interest, with the increasing concern for indoor air quality. In order to improve the indoor air quality in a realistic building, the air movement and contaminant transport in a partitioned enclosure with ventilation have been studied numerically and experimentally. A three-dimensional analysis of air movement, temperature distribution and contaminant particle transport is made to investigate airflow patterns and deposition of contaminant particle in a partitioned enclosure.

Several studies have shown that the lowest concentrations of contamination in operating theatres are achieved by using fabric covered laminar airflow systems. These systems are distinguished due to the low turbulence intensities in the protective areas. An examination in a special designed test facility was done to get further information about the relation between the turbulence intensity and airborne contaminations. In a first stage the dispersion of airborne contaminations was examined.

The occupants of buildings are exposed to a range of aerosol contaminants, of both indoor and outdoor origin; at present, filtered mechanical ventilation is the only effective means of airborne particulate control in polluted urban areas. Significant energy costs may be incurred, however, through the large pressure drops associated with membrane filtration. An alternative to filtration might be the enhancement of aerosol deposition on a protruding surface which is parallel to the incoming airflow direction, but which does not significantly retard the airflow.

Microbial monitoring of the indoor environment can be performed in several ways and with the aid of different techniques. Knowing the limitations of the chosen system is of vital importance for the correct evaluation and interpretation of the results. The number of Colony Forming Units (CFU) detected by one method can not be directly compared with results from another method. The paper presents an evaluation of commonly used instruments for the collection and counting of airborne viable particles.

A study of air movement and aerosol particle distribution and migration in a ventilated two-zone chamber is presented. The comparisons of average particle concentration decay between numerical results and measured data are generally satisfactory and acceptable. It can be concluded that the particle distribution and migration are mainly influenced by the airflow pattern and ventilation rates.

Concentrations of indoor air contaminants are normally calculated by assuming that they fullyfollow airflow paths in a room. This assumption is also used to predict the local residence timeof contaminants in a room, which may further be used to characterise the ventilation effectiveness.In this paper, a different methodology has been adopted, in which indoor airborne particles do notalways follow the main airstream induced by the ventilation system. Dispersion of particles ispredicted by a drift-flux model.

To evaluate the health risk posed by particles emitted from sound absorbent materials used in ventilation channels, the number, size, shape and composition of fibers and other particles must be characterized. A method of studying those particle characteristics has been developed. The number concentration of small particles in the testing chamber was measured with a condensation nucleus counter. Both scanning electron microscopical and optical microscopical analyses were possible for filter samples because of the low particle concentration of background particles in the testing chamber.