In the TV show Breaking Bad, Walter White, a high school chemistry teacher learns he has stage three lung cancer, so expecting to die in the not too distant future he decides to make some money for his family by making and selling methamphetamine.
The cooking of meth involves a chemical reduction of pseudoephedrine or ephedrine via red phosphorus and hydriodic acid. Red phosphorus is produced by heating white phosphorus, which on its own can self-ignite catch fire but when it is mixed with sodium hydroxide, phosphine gas is produced.
Phosphine is a flammable gas with a lower explosive limit of 1.8% by volume, but it is also highly toxic with an eight hour occupational exposure limit of just 0.1ppm and is immediately a danger to life and health (IDLH) at 50ppm.
In industry phosphine is found in the semiconductor industries where it is used as a precursor for the deposition of compound semiconductors, but it is most commonly found being used as a commercial pesticide. Phosphine is an attractive fumigant because it is lethal to insects and rodents, but ultimately degrades to phosphoric acid, which is non-toxic. It is widely used in the shipping of materials, typically being added before embarkation and killing any unwanted creepy crawlies whilst on the way to its destination.
Phosphine is only fully effective if a lethal concentration is maintained for a period of time that can be as little as 3 days or as much as 3 weeks. The actual time needed will vary according to the cargo temperatures, insect species that may be present, and the system of fumigation. This is the reason why fumigation with phosphine is almost always carried out during the voyage so that the voyage time can be used to ensure a fully effective treatment. It is routine therefore to check cargo containers for any residual phosphine before they are unloaded.
While Walter White's on a ride-along with his DEA brother-in-law Hank Schrader, Hank mentions that a meth lab can be dangerous on a good day because if you mix the wrong chemicals, you get mustard gas. Walt corrects it to phosphine gas which Hank comments can kill you if you get one whiff of it.
Later, when forced to cook meth by the gangsters Krazy-8 and Emilio Koyama, Walt mixes red phosphorous into a pan of water he has over a burner after taking and holding a deep breath. While Walt escapes, Krazy-8 and Emilio fall victim to the phosphine gas created by the combination. Walt holds the door closed so to prevent escape, and both men eventually succumb to the poisonous gas.
So whether its fruit flies or fly guys, phosphine is used to kill them all, and is so good at it that anyone else working in an environment where it is present definitely needs to be able to detect it and protect against it.