The propagation of low-amplitude air pressure transients within the drainage and vent systems of underground habitable structures may result in system failure due to trap seal loss and foul odour ingress into the occupied space. This paper develops the simulation of such transient response, and presents comparisons between predicted system air pressures and those monitored during the operation of the drainage and vent system in a large London Underground tube railway station.

A cautionary tale of what happens when the entire construction and development system breaks down.

Describes the development of the Swedish duct tightness guidelines, the "AMA system". The latest version, due in 1998, aims to increase tightness requirements once again by introducing a tightness class D as the standard requirement for larger spiroduct systems. The concern about an increasing part of the Swedish population becoming allergic and asthmatic led to the Swedish Parliament introducing compulsory inspections of ventilation systems in 1990.

Traditionally, ventilation and air conditioning ducts have been manufactured with rectangular cross sections. The rectangular duct can easily be adapted, e.g. to restricted ceiling voids and plant rooms, however, often at the cost of efficient airflow design and possible cost savings. A round duct system normally performs better and offers a more economical solution, which is the reason why it always pays to study and compare the ductwork design before selecting which type is to be used for a specific application.