The Swiss cheese model is a organizational model, proposed by James Reason of the University of Manchester and Dante Orlandella[1], used to analyze the causes of systematic failures or accidents, commonly used in the fields of aviation, engineering and healthcare. It describes accident causation as a series of events which must occur in a specific order and manner for an accident to occur, which it compares to the holes of several unique pieces of Swiss cheese lining up. A system is analogous to a stack of slices of Swiss cheese. The holes are opportunities for a failure or accident to occur, and each of the slices are layers of the system[1]. A 'hole' may allow a problem to pass through a hole in one layer, but in the next layer the holes are in different places, and the problem may be stopped. Each layer is a defense against potential problems.[2]
For a catastrophic failure or accident to occur, the holes need to align for each step in the process allowing all defenses to be defeated and resulting in an error. The model differentiates between two types of 'holes', latent failures and active ones. Latent ones are existing problems, and active ones are the acute failures that lead to an accident[1] If the layers are set up with all the holes lined up, this is an inherently flawed system that will allow a problem at the beginning to progress all the way through to adversely affect the outcome. Each slice of cheese is an opportunity to stop an error. The more layers, the less likely an accident is to occur.
Although the Swiss cheese model is respected and considered to be a useful method of relating concepts, it has been subject to some criticism, including that it is used over broadly, and without enough other models or support. However, it is viewed as a decent model when supported.[1]