Commonly this pressure is 0.25 inches of drinking water column, but is often lifted or lowered as the procedure demands. Isolators need to be periodically leak tested to guarantee their integrity and stop escape in the decontamination agent. Leak testing can be done by many methods like stress decay https://medium.com/@tailinscitech/applications-and-benefits-of-tailin-containment-isolator-for-handling-high-potency-materials-8c66a55dbcf7