Windy Skies cannot get third-party prior reference for any true advance. By that moderation criteria, Galileo himself would not have been allowed to post here, as he first wrote of his discoveries.
The Austin Robot Group had early access (1980’s) to super-sensitive gas detectors from Motorola labs for our robotic blimps. We played with them briefly, but they did not prove operationally useful. The simple way to tell if your envelope is losing gas is just let it sit, and the pressure drop will soon be apparent in the stiffness of the membrane.
Top of an LTA envelope is always “higher than atmospheric pressure” in normal use, even for rigid airships with slack in their gas bags.