It also depends on how long and how frequently you've smoked. If it was one hit, one time only and ever, should be out of your system for a urine test within a couple weeks, if not days. If you're asking how long you stay high off one hit...depends on the weed and how often you smoke. But, usually not very long.
Manufacturers often design e-cigarettes to look like regular cigarettes, but they contain no tobacco and don't require a match -- or any flame at all. An e-cigarette is a battery-powered device that converts liquid nicotine into a mist, or vapor, that the user inhales. There's no fire, no ash and no smoky smell. E-cigarettes do not contain all of the harmful chemicals associated with smoking tobacco cigarettes, such as carbon monoxide and tar.
Thornburg and his colleagues tested the vapor from e-cigarettes using a new smoking machine built to replicate the physical experience of a 14-year-old boy using one of the devices. They first tested an e-cigarette liquid designed to create a tobacco flavor. That liquid produced particles about 184 nanometers in size.