Part of the problem is a misunderstanding of the duct tape and plastic sheeting to seal up a room. Yes you can seal it up well enough to die by using up the air inside and that is how the design is suppose to seal a room.

The errors come from the idea is this is for all situations. The original design was for shelter rooms in case of chemical attacks nothing else. The idea is that most military chemical attacks do not use what are called presistant agents. That means that they disipate in a short [a couple of hours] so your own troops can move in without the need of protection gear. The idea originated and has been most used in Israel speially during the gulf war.

The idea is for short term duration and being cheap enough for large masses of people. Even something like a dirty bomb it can allow the majority of the contamination to settle. Then you can would have time [such as an attack in the middle of the night] to don protective gear, plan an escape route out of the effected area. and then exicute it as quickly as possable. Thus minimizing exposure. The time such a shelter would provide will allow a more controlled and efficent escape over a grab and run situation.