Chemical reactions

People should be careful with chemical reactions because they can do something good or something bad after the reaction. Like in some restaurants or homes they still mix Clorox and Ammonis to clean, until is too late and there's people dead or in a hospital. Those 2 things make chlorine gas and other bad things that can kill you. We use chemical reaction like burning gasoline for cars, but they dont do anything bad or using copper as tubes for water. Those 2 dont do anything bad to kill you.
http://chemistry.about.com/od/toxicchemicals/a/Mixing-Bleach-And-Ammonia.htm