Generally this pressure is 0.25 inches of drinking water column, but is usually lifted or reduced as the process involves. Isolators have to be periodically leak tested to make certain their integrity and forestall escape from the decontamination agent. Leak testing can be done by several methods such as https://medium.com/@tailinscitech/applications-and-benefits-of-tailin-containment-isolator-for-handling-high-potency-materials-8c66a55dbcf7