I was cleaning out a chemical storage closet at work. A hydrogen chloride container leaked out onto some iodine containers. I picked one up (bare handed) and sat it down in the grass. About thirty seconds later, I noticed the steam boiling up from around the bottom of the container. This is about 45 seconds worth of contact.
I thought it was terrifying because this was a footprint of someone who was lurking around your house, looking through your windows.