Measuring and testing – Gas analysis – Gas of combustion
Patent
1996-02-28
1997-07-01
Williams, Hezron E.
Measuring and testing
Gas analysis
Gas of combustion
73 101, 73 106, G01M 1900
Patent
active
056440715
DESCRIPTION:
BRIEF SUMMARY
The invention relates to a method of generating smoke aerosols, particularly for the design, testing or demonstration of fire alarm systems, in which a test material is pyrolysed by heating the smoke aerosols thus being released, and to a pyrolysis apparatus for carrying out this method. For proper design and testing as well as for demonstration of fire alarm systems it is known to carry out smoke tests with a method of the type already mentioned, test material, for example a piece of electrical cable or a board, being heated until a smouldering fire arises during which smoke is generated. As the causes of fires in electrical or electronic installations are always overheating conditions on cables, soldering points or the like, the smoke tests are also carried out with such components as test material. During the design of fire alarm systems, the tests serve to ascertain where the detectors are to be located in the electronic installation or in the room in which the installation is positioned. Every installation, and also every room, due to the geometry, differing equipment with electronic and electrical components and due to the most varied types of air conditioning equipment, there are differing flow conditions, which must be taken into account in the design of fire alarm systems. When testing fire alarm systems the tests enable it to be ascertained whether the detectors installed are still in the correct position in the electronic installation or in the room after, for example, the disposition of the electronic installations in a room has been changed or new ones have been added. Within an electronic switchbox as well, the flow conditions are influenced for, example, by the fact that a board has been inserted or removed. Certain government regulations prescribe such tests for danger warning systems, i.e. also for fire alarm systems, at regular intervals. Finally, the tests named above serve to demonstrate the effectiveness of a fire alarm system, in order to have a positive influence on the decision of a purchaser to install such a system.
During the occurrence of fires, particularly electrical fires, three basic phases can be distinguished: the pyrolysis phase, in which the low-energy and invisible smoke aerosols are released, the smouldering fire phase, in which visible smoke aerosols are released, and the open fire in which smoke and flames arise. While conventional fire alarm systems, e.g. spot alarms, are activated in the last phase, the range of detection of modern early warning fire systems lies in the two first phases.
The Document DE-OS 22 04 801 discloses a method for generating smoke aerosols in a fire alarm system on the basis of ionization alarms, in which the components at risk from fire and to be protected, such as boards or cables, are treated with a smoke-generating substance which, when heated to a specific response temperature, releases visible smoke aerosols. These are then detected in a known way by ionization detectors, and an alarm is triggered.
The known method for generating smoke aerosols has disadvantages, particularly in its use in early warning fire systems, by means of which the occurrence of an overheating condition is to be detected. The weak point is the release of smoke aerosols, which is not reproducible or only inaccurately, so that it cannot be ascertained with certainty whether the response behaviour of the fire alarm system has changed since the last test or not. A further problem is the unrealistic progress of smoke generation; for this is effected extremely suddenly and at high concentration, whereas in most electrical fires the pyrolysis phase can extend over a period between hours and days, until a smouldering fire with visible smoke development occurs.
The purpose of the invention is to improve a method for generating smoke aerosols of the type already mentioned in such a way that a reproducible burning behaviour is achieved, as well as to indicate a pyrolysis apparatus for carrying out the method.
This purpose is fulfilled according to the invention by a metho
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Wagner Alarm-und Sicherungs -systeme GmbH & Co.
Wiggins J. David
Williams Hezron E.
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