The symptoms of nicotine overdose are some combination of:
- nausea
- dizziness
- headache
Some people also get the hiccups as an early warning sign. Overdose is quite unpleasant, but it's exceedingly difficult for most people to get a toxic level of nicotine from
vaping (drinking it would be a different story). With
vaping, it takes effect so quickly that you feel dreadful and stop
vaping before you get to a harmful level. If you do get 'nic sick', put down the vape and you should feel better within about 20 minutes. Then start again with less vaping or lower concentration juice.
You're correct that older equipment generally delivered less vapour. Current setups usually fall into three categories:
- Pod mods: low power, deliver little juice and therefore usually use high concentrations of nicotine in the range of 25 mg/ml - 50 mg/ml, which is sometimes written as 2.5% - 5%
- MTL: the middle option; nicotine levels are most often 3 mg/ml - 20 mg/ml
- DL: high power, lots of ejuice per puff so less nicotine per ml; often 1.5 mg/ml - 6 mg/ml
Older equipment fell in the lower-powered end of the modern MTL range, and ejuice at the time could go up to 24 - 30 mg/ml for some people.
Can you tell us what tank you're using? I'm wondering if it's MTL or DL.
Izan's recommendation is a solid strategy. Vape whenever you crave an analog and see if you can get by with that instead. The 'right amount' of nicotine is enough to keep you off the cigarettes and not enough to make you sick.
Good luck!