Domenic_S that's reasonable for a single group in a well ventilated area.
However, your friends are not the only smokers. A doorman may be slightly down wind of a 'smokers area' which get's a long swath of people over the day. Sure, he might get 0.1mg per smoker but multiply that by 200 people who go out twice a day and that's 40mg which is probably not lethal but still plenty to cause issues. Not to mention withdrawal issues on his days off.
In terms of e-sigs, the second hand dose is likely lower. Assuming the unregulated doses are as described. But, if people assume a poorly ventilated break room is ok then people who work next to it may also get a fairly high dose.
You forgot to divide by the volume of the vapour-cloud, there, as the hypothetical doorman is not getting his nicotine mouth-to-mouth from each smoker in turn.
This volume increases by the third power of distance--give or take a factor of 3 depending on wind strength and direction, it'll roughly be a cone of sorts.
So start with the quoted-above 2.25mg per hour of "in your face" nicotine, which we'll assume you could ingest if you keep breathing within a cubic foot (0.028 cubic metre) of a single smoker's mouth for the entire hour.
Say the doorman is standing 25m (~80ft) away. (if he lets a crowd of smokers gather much closer to his door, he's not really doing his job properly)
So that's distance times 80, meaning volume times 512,000. But it's a wispy wind-blown cone gushing in the specific direction of our poor doorman, so divide by 3, is 170,000 times the volume.
THEN, you multiply by the busy number of 200 people that are there all the time (very busy smoker's spot, this).
I get 2.6µg per hour. But only on the days when the wind has it in specifically for him. Standing within 25 metres from a crowd of 200 people constantly smoking e-cigs all day.
Two different situations. One a bunch of people smoking outside. Where each sig release 11-19mg of smoke with 500mg being a potentially lethal dose. And someone near it getting 1/2% of that is reasonable.
Case two, people thinking e-sigs are 100% safe and smoking inside.
In both cases each persion thinks there harm is meaningless but they add up.
However, your friends are not the only smokers. A doorman may be slightly down wind of a 'smokers area' which get's a long swath of people over the day. Sure, he might get 0.1mg per smoker but multiply that by 200 people who go out twice a day and that's 40mg which is probably not lethal but still plenty to cause issues. Not to mention withdrawal issues on his days off.
In terms of e-sigs, the second hand dose is likely lower. Assuming the unregulated doses are as described. But, if people assume a poorly ventilated break room is ok then people who work next to it may also get a fairly high dose.