The Bird's Pyramid, also called accident pyramid theory, Frank Bird's pyramid and Heinrich's pyramid, is a graphic representation that indicates that prior alerts underlie a fatal accident.

Developed by Frank Bird, in 1969, based on the study of 1,750,000 people where it was concluded that, for every fatal accident, 10 serious accidents occurred and for every 10 serious accidents, 30 minor accidents occurred: that is, statistically, in a company where too many incidents occur, serious accidents will occur.

The levels of the pyramid show that to eliminate the most serious accidents, minor accidents must be prevented. The pyramid contains the following levels:

1 represents fatal accidents, which can be fatal or permanent disability;

10 are serious accidents, with loss of time, with or without material damage;

30 are minor accidents, with material damage, with or without injury;

600 are those risk cases where no injury or damage occurred.

The last level is made up of unsafe conditions, the amount of which is not easy to determine, since there is no general parameter for their creation or occurrence and, for an incident or accident to be generated, there may be one or several acts and unsafe conditions.

Frank Bird's theories have been very popular in the 1970s, although they were subsequently subject to critical reviews such as:

In general, it is criticized that the emphasis on the prevention of low-impact incidents - such as slips and falls at the same level - is detrimental to investment in technical and organizational improvements. Contrary to Heinrich's statement above, in industries affected by major accident risks there are significant differences between major accidents and minor incidents: these differences include: the activities involved, the amounts of energy released, the characteristics and number of safety barriers that were or could have been relevant to the event. Bird and Heinrich's ideas may lead some companies to focus excessively on individual behaviors (behavioral safety) instead of providing safety barriers. independent of human behavior, which is fallible by nature. Serious accidents in high-risk industries are generally caused by factors very different from “unsafe acts” and their management requires specific actions that are not related to behavioral safety.