The vapor pressure of mercury is extremely low. It would take a long time for mercury to evaporate.
How many of you as kids played with mercury. Did it evaporate?
The vapor is poisonous, but staying away from it for 20 minutes does not resolve the problem.
What is this “professor” smoking?
We played with mercury, rubbing it onto dimes with our fingers. It made the silver dimes very shiny. We then spent the dimes after tiring of them. Hey, we were kids and didn't know any better. I don't recall seeing it evaporate.
I’m guessing it’s a mercury compound rather than metallic mercury, so it might have different properties.
True enough, but the rate at which the mercury evaporates is also affected by the surface area of the sample.
A cup of mercury sitting on the table exposes only its top surface to the air, and very little vapor comes off. But tip that cup over and spill it on the floor and you have a different situation.
Mercury splatters enthusiastically, much more so than water, for ex., and it forms lots of tiny droplets that scatter everywhere. Each one of those has its own (approximately) spherical surface which ramps up the evaporation rate quite a lot.
One solution that I have heard of is to keep flowers of sulfur handy and scatter that over the spill. It reacts with the mercury to form the harmless sulfide, which you can sweep up later.
The mercury in a CFL is miniscule, but if that bulb shatters it splatters, and if it was lit at the time, the stuff is already vaporized. So you will get a snootful from it if you're in the area.