This is depressing: police are being warned that "detergent suicides" can be hazardous to their health as well. According to the Daily News, an internal order says many people who decide to kill themselves in this manner are often courteous enough to post warning signs so anyone entering knows to watch out for deadly fumes. But the NYPD's Weapons of Mass Destruction Team allegedly determined the technique could be used to intentionally kill officers in confined spaces, such as elevators or subway cars. The mixture of household cleaners and detergents creates hydrogen sulfide, a colorless, flammable, poisonous gas which often smells of rotten eggs.