latex vacuum bed?

These devices often come with a caution that they shouldn’t be used for self-bondage, but I’m wondering if perhaps they CAN work this way.:idea: To keep the seal completely tight, the vacuum cleaner must stay on.. so I’m curious what happens when it turns off? Has anyone here tried vac-beds before? Does air rush back into the bed, making movement possible again? It would be simple to install an on/off timer on the power socket. Since my home uses metered electricity, if the credit runs low, the power cuts out after a few hours automatically. The cost is around $400-$600 (roughly £230-£340), which isn’t too steep, but I’d like to confirm my assumption before testing one. It would be easy enough to place some items inside and see how long it takes for the seal to fail (IF it fails!) - though I want certainty before purchasing. :?