“Easy span” is a permeation tube type and it may be used at room temperature: the permeation rate is low with a linear dependence of the temperature. To change permeation rate is possible to keep the tube into  thermostatic bath to obtain a know mixture. “Easy span” is available for organic substances liquid at room temperature also deuterate, with permeation rate from ng/min at μg/min. Each tube is supplied with a tee Swagelok® connection (¼ inch) and calibration certificate with a graph which shows permeation rate vs. temperature from 16 to 25 °C