Permeation tubes are designed for gas calibration standards
VICI Metronics
During gas chromatography, calibration gas standards are used to establish a reference point for analysis verification. Dynacal Permeation Tubes (photo) are small, inert capsules containing a pure chemical compound in two-phase equilibrium between its gas phase and either its liquid or solid phase. At a constant temperature, the device emits the compound through its permeable portion, at a constant rate. Accurate, stable concentrations range from parts-per-billion to high parts-per million, says the company. Rates can be certified using standards traceable to NIST, using accurate laboratory procedures, says the company. — VICI Metronics, Poulsbo, Wash.