The reintroduction of toxic gases emitted from roof stacks can significantly affect the quality of the air inside a building. The determination of a safe distance between the sources of pollution and the fresh air intakes is based on a complex exercise that must take into account several wind, physical and topographical factors. Estimates of maximum concentrations as a function of downwind distance from a stack can be obtained using empirical models provided by the American Society of Heating, Refrigerating and Air Conditioning Engineers [ASHRAE, 1997](1).

Many hazardous chemicals are used in research laboratories. Fume hood is the most efficient and common single equipment used in prevention of chemical exposure of laboratory workers. Totally 303 fume hoods were inspected at the University of Kuopio laboratories and 295 of them were tested for their performance. The most important properties affecting occupational safety due to the fume hoods were tested.

In North America, there is an ongoing effort to repair the effects of corrosion in large boilers and pressure vessels. In recent years this work has been done from scaffolds erected in the boiler or vessel. The largest pressure vessels in British Columbia are known as Kamyr Digesters, and are found in Kraft pulp mills. The boilers are found in pulp mills across Canada and the USA, and in thermal power plants in east of the Rocky Mountains in Canada and across the USA. The scaffold structures are made up from 50 mm diameter steel columns and struts that are assembled with steel wedges.

A pulse pressurization technique to measure the airtightness of the building envelope is developed. The governing equations are introduced and the procedure for deriving airtightness parameters from the pressure decay curve is shown. Pulse pressurization is supplied using a high-pressure air tank. The pressure decay after pulse pressurization is measured provides the air leakage equation for a test house.

A great deal of the literature on general ventilation expresses the adequacy of the volumetric flow rate of air in terms of the number of room air changes per hour. Although the concept of air change rate has very little relevance to the control of contaminants as it relates to the size of the room and not to the scale of the problem, the overall amount of air entering and leaving a workplace is of fundamental importance in assessing the quality of the working environment.

Zonal models are often used in analytical calculation of temperature, concentration or humidity conditions in ventilated spaces. The space is divided in two or several zones ( 1 ). The zoning of the space is based on the assumption of constant temperature,  concentration and humidity in each separate zone. The balances for air mass flow, contaminant mass flow, water vapour mass flow and heat flow are determined between zones and between zone and outer boundaries.

The ventilation efficiency in a displacement ventilated room with non-buoyant pollutant sources was evaluated under laboratory conditions. The contaminant removal effectiveness was measured for different positions of the pollutant sources and with different ventilation flow rates. The air change efficiency and the temperature gradient in the room was measured for the different ventilation flow rates. The contaminant removal effectiveness was much dependent on the position of the sources and varied from 30 to 240 %.

Nicotine concentration in air has been measured in several restaurants by different measuring techniques. Several problems of the measuring techniques has to be solved before nicotine measurements can be used for approval purposes. For approval purposes, the checking of the ventilation may be more fruitful than nicotine measurements.