That part struck me as embellished writing (or perhaps the tour guide exaggerated that point). I hardly know a thing about the sensitivity of explosive weapons,

That part struck me as embellished writing (or perhaps the tour guide exaggerated that point). I hardly know a thing about the sensitivity of explosive weapons, but consider the importance the Soviets placed on secrecy. If there was such a danger, I can't imagine them working so hard to construct the place in near-total obscurity, and subsequently relegating the safety of up to six submarines and up to 3000 people to the accuracy of a single hair. Although, having looked it up now, hair-tension hygrometers could be a bit more accurate than what I initially guessed, though there are more accurate alternatives.