Cerberus Ag

Sigfrid Strassler

Martin Forster

Gustav Pfister

Hannes Guttinger

Peter Ryser

Alan P Troup

To improve probability of detection in the early stages of fires, a fire alarm (1) with a temperature sensor (3) is proposed, having a structural member (12) that causes the sensor (3) to react only to temperature changes in the ambient air, and which change with a frequency of from 0.1 to 20 Hz. The fire alarm (1) becomes particularly insensitive to errors when there is a second fire sensor (7) that reacts to fire aerosol, there being a threshold value circuit (9) that lowers the threshold value for the fire aerosol sensor (7) when the temperature sensor (3) exceeds a preset threshold value.

Method of detecting fire in an early stage

Reducing gases can be detected in a gas mixture to be investigated, particularly in air, with high sensitivity and precision by means of a gas detector. The gas detector comprises a gas sensor which is arranged within a measuring chamber. The temperature of the gas sensor can be continuously increased according to a predetermined pattern from a starting value to an upper threshold value and can be subsequently decreased again to the starting value according to the same or according to a different pattern. There are provided at least two such heating cycles. Simultaneously therewith the gas mixture to be investigated, which is present in the measuring chamber, is periodically exchanged against a pure reference gas which is contained in a reference chamber. A selected property, such as the electrical conductivity of the gas sensor is thereby periodically changed. The temporal variation of this periodically varying electric conductivity can be detected in an evaluation circuit arrangement and/or evaluated for determining the concentration and/or the nature of the reducing gases which are present in the gas mixture to be investigated.

Method of, and apparatus for, detecting reducing gases in a gas mixture

An aerosol detector, for instance a transmission measurement path in a measurement chamber, is provided for the detection of a foreign component in a gas, for instance of incendiary aerosols or smoke in air, and communicates with a reference chamber containing aerosol-free reference gas. The gas in the measurement chamber is periodically exchanged for uncontaminated gas from the reference chamber by a periodical volume alteration of the reference chamber so that, in the presence of aerosols, the aerosol concentration in the measurement chamber and the output signal of the aerosol detector are modulated. The modulation, i.e. the variable portion of the output signal, is an indication of the aerosol concentration or the smoke density. A particularly suitable application is smoke detection in air for the purpose of fire or incendiary reporting or for monitoring air pollution.

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Baden-Dattwil, Switzerland

Sigfrid Strassler