manufacturing variability affect a resistor; they do not affect software. Failure modes with identical effects can be combined and summarized in a Failure Mode Effects Summary. When combined with criticality analysis, FMEA is known as Failure Mode, Effects, and Criticality Analysis or FMECA, pronounced "fuh-MEE-kuh". Fault tree analysis Fault tree analysis (FTA) is a top-down, deductive analytical method. In FTA, initiating primary events such as component failures, human errors, and external events are traced through Boolean logic gates to an undesired top event such as an aircraft crash or nuclear reactor core melt. The intent is to identify ways to make top events less probable, and verify that safety goals have been achieved. Fault trees are a logical inverse of success trees, and may be obtained by applying de Morgan's theorem to success trees (which are directly related to reliability block diagrams). FTA may be qualitative or quantitative. When failure and event probabilities are unknown, qualitative fault trees may be analyzed for minimal cut sets. For example, if any minimal cut set contains a single base event, then the top event may be caused by a single failure. Quantitative FTA is used to compute top event probability, and usually requires computer software such as CAFTA from the Electric Power Research Institute or SAPHIRE from the Idaho National Laboratory. Some industries use both fault trees and event trees. An event tree starts from an undesired initiator (loss of critical supply, component failure etc.) and follows possible further system events through to a series of final consequences. As each new event is considered, a new node on the tree is added with a split of probabilities of taking either branch. The probabilities of a range of "top events" arising from the initial event can then be seen. Oil and gas industry offshore (API 14C; ISO 10418) The offshore oil and gas industry uses a qualitative safety systems analysis technique to ensure the protection of offshore production systems and platforms. The analysis is used during the design phase to identify process engineering hazards together with risk mitigation measures. The methodology is described in the American Petroleum Institute Recommended Practice 14C Analysis, Design, Installation, and Testing of Basic Surface Safety Systems for Offshore Production Platforms. The technique uses system analysis methods to determine the safety requirements to protect any individual process component, e.g. a vessel, pipeline, or pump. The safety requirements of individual components