Normally this tension is 0.25 inches of water column, but is often elevated or decreased as the process needs. Isolators have to be periodically leak tested to guarantee their integrity and stop escape of the decontamination agent. Leak testing can be done by various methods such as tension decay https://tailinscitech.weebly.com/blog/applications-and-benefits-of-tailin-containment-isolator-for-handling-high-potency-materials