Valvu ndi imodzi mwa mavavu abwino kwambiri ogwiritsidwa ntchito mafakitale monga kutentha kwa mzinda, mpweya wa mzinda, makampani opangira mankhwala, mphamvu, mapaipi a mpweya wachilengedwe, makampani ovula, chakudya, nsalu ndi zina zotero. Pambuyo pa zaka zambiri za mayeso a msika, khalidwe la mankhwala likufika pamlingo wofanana ndi mankhwala ofanana kunja. Choncho ili ndi mbiri yabwino pakati pa ogwiritsa ntchito.

Makampani a nyukiliya, makampani a mankhwala a mafuta, makampani a zamagetsi ndi makampani a ndege, komanso ukadaulo wa njira basi. . . . . . kufunika kwa mavavu a mafakitale padziko lonse lapansi, kuphatikizapo kubola.