Leak detector for extremely toxic gases

Even very small leakages in manufacturing plants are most unwanted. Whenever a flange, tube or valve is suspected to be leaking, it must be checked with a leak detector, and the potential leak must be located.

If a plant handles very toxic substances, such as phosgene, hydrogen cyanide, chlorine or chlorine dioxide it is therefore essential to have an extremely sensitive leak detector on hand.

Sensors as used in common leak detectors may not do the job, as they have interferences to gases that may be present in normal industrial atmosphere, for example hydrogen, hydrocarbons, carbon monoxide or carbon dioxide. These gases may create such a strong signal, that the signal created by the emission of a small leak is overlaid – the leak is overlooked.

To locate small leaks, a sensor technology as well highly sensitive as specific is required.

Elektrochemical sensors can do this job, if the appropriate materials for electrodes and electrolyte are selected. Phosgene sensors for instance use silver as working electrode material, embedded in a special electrolyte gel.  Thus very specific sensors can be made with a detectable limit for phosgene as low as 2 ppb! This sensor has no interferences to humidity, hydrogen or hydrocarbons.

A disadvantage of electrochemical sensors is their slow response compared to physical methods of detection. As a matter of fact, the material transformation at the working electrode takes some time.

Tests have shown, that this process can be speeded up, by feeding the gas to the sensor by a sample pump. The new Tracer sensor operates in a measuring chamber the shape of which has been optimized for fast response. Indeed the Tracer responds almost as fast as an instrument with a physical sensor.

To locate a leak, the sampling probe intake of the sensor must be moved along the surface to be inspected. An increasing measured value indicates approximation to a leak. The same time the frequency of the beeper and LED increase, similar to a Geiger counter.

To avoid the leak detector - which might be exposed to very high concentrations of the target gas - can be abused as a personal monitor, the display has no units. It shows zero to 100 % range or a bar graph.

The Tracer is available for the following gases, each in a high or low range version:
COCl₂, HCN, HCl, Cl₂, NO₂, ClO₂ und H₂S.