Description

Permeation tubes are small containers filled with a pure chemical compound in a two‐phase equilibrium between its gas phase andliquid phase. The containers are in suitable inert polymeric material and at a constant temperature; the device emits the compoundthrough permeable wall with a constant rate.

The permeate is mixed with a carrier gas at a controlled flow rate to obtain a known mixture used as reference in gas testing equipment. A wide range of permeation rates can be made, normally from 20μg/min to 500 μg/min, and accurate, stable concentrations range from ppb to high ppm.

Bendfits

Advantages of permeation tubes :

Use pure substances in an inert matrix

− Precise concentrations;

− Easily generated with traceablity established from protocol U.S. EPA‐

600/R‐97/121, Section 3, procedure P3 (see calibration certificate)

− Several tubes can be used simultaneously to obtain a mixture, removal

and/or addition of a single component is simple

− Wide range of concentrations easily generated by varying the dilution

flow rate and/or the set point temperature;

− Consistent concentrations for extended periods of time

− A relatively inexpensive source of standard gas.

Applications

Often the gas standards in cylinder mixtures are very reactive and instable, especially at low concentrations. Permeatiion tubes are ideal devices in generation of calibration gas standard for:

− air quality analyzers and gas analyzers;

− FTIR;

− gas chromatograph;

− GC‐MS;

− Ion Mobility Spectrometer.

With permeation devices is possible modify the mixtures components simply removing and/or auditioning a single tube in permeation chamber. Permeation devices are utilized in:

− petrochemical plants and refinery;

− semiconductor industry (trace moisture standard);

− gas sensor development ;

− test with controlled atmosphere; Catalyst test with synthetic gas.