When should I use an inert gas (nitrogen) blanket with a Huber bath unit? In open bath circulators, oil (thermal fluid) is exposed to the atmosphere. At high temperatures, the oil can be degraded, and there is also a small risk it can become gel like. For the common Huber silicone oils, we recommend the use of inert gas (a nitrogen blanket), particularly if you will be working at temperatures over 150°C, to prolong the lifetime of the oil. We can supply bath covers with fittings (an inlet and an outlet) for inert gas as custom; please contact us for further details.