In applied physics and engineering, an improvised apparatus is one that solves a problem using existing tools and materials. Examples include heating using a gas cooktop instead of a Bunsen burner or using a DC battery and mechanical pencil lead to electrolyze water.
Improvised apparatuses may prove critical to survival in life or death situations. Examples include the re-engineering of carbon dioxide scrubbers using on-hand materials during the Apollo 13 mission to avert carbon dioxide poisoning or the usage of a knife to turn a screw.
Obsolescence without a definitive replacement plan may lead to improvisation. An organization incapable of purchasing a new computer system or vital software may upgrade its existing architecture using in-house ingenuity, thereby extending the lifetime of this existing equipment. Such improvisation may also arise if manufacturer support is no longer available for the existing product.
Improvised apparatuses may also result from censorship or embargo. Military forces may improvise explosive devices that are constructed and deployed in nonconventional ways. Such tactics are popular among rebel and guerrilla forces that have limited access to state-of-the-art weapons.
Fields with a highly accelerating rate of innovation, such as communications and computer science, require more frequent upgrading or replacement than those in less accelerated fields, such as music or traditional crafting.