[Aachen]

    $ qalc
    > 100 kg / 680e3
    approx. 147.06 mg

Each puff would be <150 milligrams if the tanks were empty now, and since they're not... that's some small puffs!

(Not sure what the USA weight unit is, stones or something? DDG says that's 0.000024 stones)

[unwind]

Probably ounces ("oz") for something like this, so around 0.005 oz then. The original 100 kg is equivalent to 220.5 lbs (which is pronounced "pounds", of course).

[HPsquared]

147 mg is about 2.27 grains

[HPsquared]

Grains. 2.27 grains