Let's see...you've got a gas, dirty bomb, whatever incident in the business district of Anytown, USA and you're either in the plume or at least generally downwind. Rather than maniacally trying to seal yourself in & hoping that you don't run out of air before the all clear is given, doesn't it make more sense to grab your loved ones & a BOB and get out of the danger area? Sheltering in place is a good option in some circumstances but when there's literally danger in the air it's time to leave.

Prior to 9/11 most people would never have even considered plastic sheeting and duct taping their homes against gas yet the threat has always been present. Not neccesarily from terrorists but train derailments, truck accidents, etc. In fact, an all too common train derailment is a much more likely threat than any terrorist.

Duct tape and plastic sheeting are feel good suggestions to give the public the impression that the government is really earning the 35% of your pay they collect in taxes.

That's my two cents

Ed