Here's an interesting article about the gases produced by volcanoes. I never knew about CO2 pockets or about gases coming out of the ground near the volcano, ground that looks perfectly innocent.

you can look but don't breathe

I saw two young children at the site yesterday. That strikes me as a very bad idea.

I wonder if the gases emitted by a given volcano are steady, or do they spike and drop in concentration over time? I read that the H2S level here is three times the legal limit, but if it might spike, there is very serious danger.