Dear Isogeochem, Our Thermo bellows (reference side, Delta V plus) had a slow leak, about 2.6 mbar/min. I checked the valves around the bellows, and they should be fine. I was wondering if it is just a sealing problem which could be fixed easily? or it is a time to replace the whole bellows with a new one? Does anybody have an instruction to do it? I will appreciate it. Another question, since we normally don't need the other bellows (sample side), is it possible to swap them? Is there anything I need to pay attention when I swap/replace the bellows? Thanks a lot in advance! Wei Huang, Ph.D. Stable Isotope Lab Manager New Core Lab Rm#212 Lamont-Doherty Earth Observatory of Columbia University 61 Route 9W Palisades, NY 10964 Lab: 845-365-8143 <845-365-8306> [log in to unmask]