Alaska Airlines (hdq south of Seattle) was the first company I'd heard of to go all gestapo on nic with random testing, pre employment tests and some employees freak out about second hand smoke showing up. That was about thirty years ago when it started. The laws up there are insane. I wouldn't be surprised if someday landlords were given the right to test renters for nic.
But from what I've read, blood tests are less sensitive than urine tests, so having a little in your system isn't going to show up as promently. There is still a threshold amount, re: second hand smoke. Say your partner smokes. That'd be crazy if your employer required you to get a divorce or break off from a relationship. It might take something so ridiculous to get the point across how stupid this is.
Meanwhile I think every vaper should claim non smoking rates. Even with nicotine, it seems unlikely to be higher than second hand smoke levels. Make insurance companies figure out ways of detection because they don't have one now.
Your asorbtion rate of nic varies with how you vape as well. It doesn't all show up in plasma unless your doing lung hits. I don't fully understand this, but asorbtion in the blood is lessened with mouth/nose yet your brain still gets the benefits.
Unrelated, here's another chart I found
