A simple method for pre-calibration storage of sulphur hexafluoride permeation tubes

Long term storage of sulphur hexafluoride (SF₆) permeation tubes, used to determine enteric emissions from ruminants using a calibrated tracer (ERUCT) technique, is desirable to increase flexibility of post-manufacture tube handling. To be effective, such storage must decouple the date of tube manufacture from the date of subsequent expiration due to gas loss. We hypothesized that release of SF₆ gas could be effectively inhibited by freezing tubes at -80°C without affecting their subsequent performance. Thirty permeation tubes with mean SF₆ content of 3.081g were blocked by SF₆ content and randomly allocated to one of two treatments being: immediate incubation at 39°C, or incubation at 39°C following 75 d storage at -80°C. The SF₆ permeation rate at 39°C of all tubes was determined by repeated weighing over a 50 d period. Storage of permeation tubes at -80°C effectively inhibited release of SF₆ but had no effect on subsequent permeation rate at 39°C. Deep frozen storage offers improved flexibility in handling of SF₆ permeation tubes for the ERUCT technique. This article is part of the special issue entitled: Greenhouse Gases in Animal Agriculture - Finding a Balance between Food and Emissions, Guest Edited by T.A. McAllister, Section Guest Editors; K.A. Beauchemin, X. Hao, S. McGinn and Editor for Animal Feed Science and Technology, P.H. Robinson.