Unexpectedly, the indoor-outdoor pressure difference did not affect significantly the moisture content in different layers of two outer walls but the moisture content depended more strongly on the moisture content in outdoor.

The classification of fume hoods in laboratories was conducted as a occupational protection part of risk assessment and management procedure. The fume hoods (n = 296) in laboratories were classified according to the observed face velocities. Classification scheme included descriptions of recommended use. Only 30 % of fume hoods were recommended for normal laboratory duties and 7 % were recommended not at all to be used.

The exterior hood has been used extensively in the local exhaust devices to capture a variety of contaminants generated in a working-site. The performance of a hood can be measured by either how well it captures the contaminants or how far away it can perform an effective capture. It has been known theoretically that in the presence of an uniform cross draft a capture envelope will form in front of an exhausted opening(2, 3). All streamlines inside an envelope will lead into the opening; otherwise, those outside the envelope will lead to infinity downstream.

For the calculation of velocities in air-jets behind the ventilating outlets, the constants of ventilating outlets must be known. These constants are specified for each type of ventilating outlets experimentally. They can be usually defined from measured behaviours of axis velocities in the main area of jet, which demands to measure velocity profiles in cross flow section, in several distances from the outlet. The constants of ventilating outlets can be also defined from the air-jet extension in the main jet area behind the ventilating outlet.

When designing the outlets for the ventilation or hot-air heating of particular spaces, we meet usually the problems to specify a form and reach of the air jet and a distribution of velocities and temperatures in the space followed. In practice the calculations of nonisothermal air jets are made using a number of calculation relations to be found e.g. in lit. (1) and other. But when applying the analogical relations derived by different authors we can find out considerable differences in results.

This paper attempts to provide a general basis for implementing the principles of pressure differentials to aid in providing more user friendly air quality in buildings. This is a new technology application to be added to the commonly used air changes and filtering for cleaner air. The success story of smoke control can now be used as a major strategy against pollution and disease control in buildings. Stale bacteria-infiltrated air can also be contained to its spaces of origin and exhausted from its sources in the building.

The aim of this study was to find out the indoor air quality in the real estates of the state and what was the effect of ventilation to the indoor air quality in these buildings.

New laboratory test methods using different dusts have been developed for measuring and classifying air filters but could give very misleading results compared with filter behavior in an installation. The paper describes the differences between laboratory tests and performances in atmospheric air. It provides a basis for a better understanding of air filters and filter testing to meet IAQ problems and to reflect a filters' behavior "in service".

The influence of the electrostatic forces on airborne particles have been known for centuries. These early discoveries have been summarized in several publications including the classical book "Electrostatic Precipitation" by White (1) and many others (e.g. 2, 3, 4). The utilization of the electrostatic force led to the development of electrostatic precipitator (ESP) which has been used for pollution control purposes since the beginning of this century. An excellent historical review about the development of electrostatic gas cleaning has been presented by White (1).