A fire monitor formed by an outer tube that communicates with a water inlet and a coaxial inner tube connected to an outlet nozzle. Water flows from the inlet into the outer tube, and then around a semitoroidal bend formed by a baffle plate and a fairing into the inner tube for discharge through the outlet nozzle. The fairing is provided on the inner surface of the inner tube and the baffle plate has a curved periphery with an inner, continuous flat surface. The semi-toroidal bend minimizes turb...

A gas sensor having a sensitive element of semi conductor type, the sensor being contained within an enclosure adapted to permit gas to come into contact with the element and incorporating means for maintaining adjacent the element, a substantially constant relative humidity.

A gas sensor incorporating a sensor element of the heated semi-conductor type has a heater for the element connectible to a variable power source, the output of which is responsive to the concentration of gas under test.

An ozone monitor including an ozone reactive surface, held within a container, which is adapted to specifically react with ozone. The surface is also adapted to fail to react with nitrogen dioxide in an amount which affects ozone quantitation by more than 20% when the nitrogen dioxide is provided at a concentration of 76 ppb and ozone is provided at a concentration of 30 ppb within a test gas.

A gas monitor includes an infra-red source enclosed within a housing having inner surfaces which are reflective. Radiation emitted from the source reflects off ellipsoidal surfaces and intermediate planar surfaces to be focussed at a sensor, being reflected five times. Radiation is absorbed by gas within the housing and a comparison of the source intensity and detected intensity gives a measure of the gas concentration. Use of ellipsoidal reflective surfaces directs emitted radiation along a plu...

A method for monitoring the toxic constituent of an ambient gas e.g. sulphur dioxide in air involves bringing the gas into contact with a solution containing one component in which the gas is soluble and an indicator having optical transmission characteristics responsive to the quantity of the constituent in solution. An electric current is then passed through a second component which is electrolysed to neutralise the solution and restore the transmission characteristics of the indicator to a da...

A sterilization monitor includes a substrate and an monitor composition. The monitor composition contains a colorant and a halogen source and undergoes a distinct color change when exposed to a peracid. The sterilization monitor can be used to monitor a sterilization process involving a peracid. A sterilization monitoring device, including a sterilization monitor enclosed in a housing having a vapor permeable barrier, can also be used to monitor a sterilization process.

A sterilization monitor includes a substrate and an monitor composition. The monitor composition contains a colorant and a halogen source and undergoes a distinct color change when exposed to a peracid. The sterilization monitor can be used to monitor a sterilization process involving a peracid. A sterilization monitoring device, including a sterilization monitor enclosed in a housing having a vapor permeable barrier, can also be used to monitor a sterilization process.

An aircraft fire extinguisher system includes a fire extinguisher bottle and an attached explosive squib which has one side connected to ground and its other side connected alternately to two constant current sources in opposite senses. A differential amplifier subtracts the voltages in two sample-and-hold circuits caused by the opposite currents to eliminate the effect of the voltage at the point where the squib is grounded. A utilization circuit, coupled to the output of the differential ampli...

A heartbeat rate monitor or personal pulse indicator comprises a transducer for detecting heartbeats and supplying an electric signal corresponding to the heartbeat rate, and a display for indicating the heratbeat rate. The display is incorporated in a watch casing which also incorporates means to display the time of day, the watch casing preferably being mounted on a wrist-strap which carries the transducer.