Analysis of changes of air velocity in ventilation ducts as a factor determining the level of safety in buildings

The functionality of building security systems focuses on the rapid and reliable identification of threats and the transmission of threat information to the system user. The shorter the time between the occurrence of the threat and the response of the system user to the threat, the greater the chance of limiting or even avoiding the damage caused by the threat. A peripheral protection element is responsible for detecting an intruder's attempt to enter the protected object. Perimeter detectors for use in intrusion and hold-up alarm system (I&HAS) are detection systems located at places where potential intruder attempts to enter an object or protected zone. Especially susceptible to attempting to force architectural barriers in buildings are windows and doors. A new approach, presented in this paper, is to measure and analyse the variation of airflow velocity in the ventilation duct with an anemometer. The paper will analyse the changes in airflow velocity in ventilation ducts as a potential source of information on the condition of the protected object. Based on the computerised measurement system, examples of time variations in the velocity of air flow in the ventilation ducts will show how the measured signals can be interpreted to define normal states and states of intrusion into a protected object by forcing a window or door in a building.