So in your particular example you can't add micromorts - you can only die once, so if you die in the first round, you don't get to play the second round. And if

So in your particular example you can't add micromorts - you can only die once, so if you die in the first round, you don't get to play the second round. And if you could, the number of known-to-be-empty-chambers and/or bullets has changed, which changes the probability. But you can add micromorts in the case where n people are playing separate games of Russian Roulette. As another example, the Wikipedia page says that this is equivalent to 1 micromort: > Traveling 6000 miles (10,000 km) by jet (cancer due to increased background radiation) If you're just trying to calculate your own risk as a passenger, you can't just multiply 1 micromort by the number of 10,000 km trips you take. But if you're operating a flight, then you can multiply it by the number of passengers on this 10,000 km flight. It has more to do with the nature of the thing you're trying to model, than it does with the nature of the unit.