The most accurate barometers use mercury, the type that use bellows are aneroid ones that can go out of calibration. It like sphygomanometers, you can't beat a column of mercury for accuracy, but we are switching over to aneroid for safety reasons.
It's not the mercury as such that is poisonous but mercury oxide which is and it's accumulative in the body, that's one of the reasons why we have had to stop servicing the mercury sphygomanometrs.
Not that many are going to be taking their barometers apart but it is potentially very dangerous compound that has a long and dangerous history, Hatter's really did go mad because they ingested the chemicals used in hat-making included mercurous nitrate, used in curing felt. Prolonged exposure to the mercury vapors caused mercury poisoning. Victims developed severe and uncontrollable muscular tremors and twitching limbs, called "hatter's shakes". Other symptoms included distorted vision and confused speech. In advanced cases, hatters developed hallucinations and other psychotic symptoms.
More of a worry for some perhaps, mercury exposure from mercury dental fillings, also known as "silver" fillings and "amalgams", is a life long threat. When a person chews, drinks, swallows and breathes, mercury released from dental fillings is absorbed by the lungs and the linings of the digestive system into the bloodstream. As they corrode, mercury fillings release ionized mercury into the saliva, tooth pulp, and gum tissues leading to the digestive system and bloodstream. So do we need this ruling well maybe not
1911 I think that this may explain it. click here It's the aneroid barometer that does not use mercury, but others do. I've got my eyes on my mother's barometer that been in the family for as long as I can remember. It's an aneroid barometer plus mercury thermometer. Hopefully the ban will not apply retrospectively!! I wouldn't put it past them.