Very helpful information. I would of thought to go to the basement. It's good to know that the chemical would be heavier than air and sink. It's tips like these, easily remembered, that are the most helpful.
Yes, a lot of the chemical casualties in WWI were from soldiers taking shelter from gas attacks in bunkers and trenches. Gas, being heavier than air, followed them right in and pooled there. Oops.
Be sure to get and read Are You Ready?!