Whenever you search for any standard do-it-at-home chemistry demo, most of the time you will come across an entry on About.com. About.com is a site that tries to gobble up pageviews so it can attract advertisers, and one method they use for doing this is to pay “guides” to write about popular topics within a particular subject area.
The guide for chemistry is Anne Marie Helmenstine, who earned a Ph.D. in biomedical sciences from the University of Tennessee. Probably sensing an opportunity to gobble up pageviews, Dr. Helmenstine jumped on the liquid nitrogen pool party story. If all she wanted to do was attract hits, that was an excellent plan. Yesterday alone, ChemBark got 21k pageviews, which is about 7-10 times what the site gets on a typical day with a fresh post. But, if your job is to educate and inform, I would not recommend writing this:
Nitrogen is principal gas in air, so it it’s quite safe on its own, but the liquid nitrogen was believed to have reacted with treatments in the pool, releasing toxic gas. How do you avoid hospitalizing your party, if you want liquid nitrogen fog? Simply add the nitrogen to ordinary water, not chemical-treated water. You’ll get fog without additional compounds. The principal risk from liquid nitrogen fog is from asphyxiation. Adding more nitrogen to the air decreases the relative amount of oxygen. This isn’t an issue so much in an outdoor pool, but should be a consideration if you have an enclosed pool. It’s safer to use a fog machine or make real water-based fog in that situation.
That is Dr. Helmenstine’s expert advice, and it is atrocious. First, there is very little chance the nitrogen reacted with the hypochlorite in the pool. Second, adding the liquid nitrogen to non-chlorinated water would have posed the same danger to life as adding it to chlorinated water. Finally, to write that this “isn’t an issue so much in an outdoor pool” is not only wrong, it is a public health hazard. The pool party disaster took place at an outdoor pool.