Innovative flow controller for time integrated passive sampling using summa canisters

摘要

To restric the entry of gaseous contaminants inside evacusated vessels such as SUMMA canisters, mechanical flow controllers are used to collect integrated atmospheric samples. From the passive force generated by the pressure gradient, the motion of gas can be controlled to obtain a constant flow rate. Presently, devices based on the principle of critical orifices are used and they are all limited to an aupper integrated sampling time. A novel flow controller which can be designed to a achieve any desired sampling time when used on evacuated vessels was recently developed. It can extend the sampling time for hours, days, weeks or even months for the behefits of environmental, engineering and toxicological professionals. The design of the controller is obtained from computer simulations done with an original set of equations derived from fluid mechanic and gas kinetic laws.