This document from the U.S. FDA specifies their safety guidelines for VEDs:
https://wayback.archive-it.org/7993/20170403201650/https://www.fda.gov/MedicalDevices/DeviceRegulationandGuidance/GuidanceDocuments/ucm072098.htm
Open the document in a browser and search for "17". You will find this sentence:
Vacuum Level – Vacuum pumps typically draw a vacuum of less than 17 inches of mercury. If the vacuum range of a new device differs substantially from that specification, manufacturers should conduct studies to establish the acceptability of the vacuum drawn by their device.
I encourage everyone who uses a VED to pay attention to this number (17). It is a rational safety limit.