Leakage area measurement by fan pressurisation becomes more difficult as the volume of a building is increased. The equipment becomes bulky, and measurements of air flow through the fan and the resulting pressure differential require more care. AC pressurisation offers an attractive alternative. However, in the case of large industrial buildings, the exterior envelope is often constructed of thin flexible sheet material, and also industrial leakage paths may have a much larger area than is found in, say, typical domestic construction.
AC pressurisation is a method for measuring the airtightness of buildings. This technique, which is also called the infrasonic method, employs a reciprocating piston or bellows to impose a sinusoidal small change in volume inside the building
The air leakage distribution in a building is, in certain circumstances, difficult to determine. One example of this is the ceiling of the dwelling illustrated in figure 1 and 2. It is almost impossible to make the ceiling perfectly airtight; thismeans that a measurement by difference is impossible. The inclined roof is not airtight at all. A rather simple and easy technique is to perform measurements using tracer gas and pressurisation equipment at the same time.
There are several methods by which the airtightness of a building can be measured. One method involves the use of a fan to pressurize or depressurize the building. This creates a known pressure difference across the building envelope. Thecorresponding air flow through the fan is measured and this is an indication of the airtightness of the building. This air flow rate can be expressed as the number of building air changes per hour, a useful unit when comparing buildings of different volumes. So far only simple methods have been employed to analyse this condition.
A single whole building pressurisation test using robust and easy to use equipment can, in a very short time, quantify the air-leakiness of the building envelope. However, such measurements do not give a direct measure of the ventilation characteristics of the building which normally requires timeconsuming and specialist tracer gas tests. This paper provides a model which makes the link between leakage measurements and ventilation characteristics and applies it to a large, industrial building constructed according to 1979 UK Building Regulations.
Literature on the various types of pressurization systems, stair use during evacuation, and code requirements was reviewed and summarized. Non-fire and fire tests were conducted in the 10-story experimental fire tower of the National Fire Laboratory of the National Research Council of Canada. The flow resistances of an open stair door at various angles were measured. Under fire conditions, the vertical profiles of pressure differences across the stairshaft wall and those of the velocity pressure at the stair door opening were measured.
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