Safety precedence sequence

The fourth fundamental involves something called the safety precedence sequence. It is a prioritized list of controls that should be considered and applied, in sequence, to eliminate or control identified hazards. 

For most operations, a combination of controls must be used. Correct application of the safety precedence sequence dictates that lower-level controls are not considered until all practical efforts have been exhausted at higher levels. 

The safety precedence sequence originated as part of the system safety effort and is one of the few tools that is common to nearly all system safety efforts. 

It is not, however, always called the safety precedence sequence. It is also known as the system safety precedence, the hazard reduction precedence sequence, the hazard control precedence sequence, fhe risk control sequence, and several other names. The fifth step (accept residual risks) is not always included. 

Safety is achieved by continuing to use the safety precedence sequence to control hazards until all identified hazards are eliminated or controlled to an acceptable level and residual risks are formally accepted. The detailed procedures for hazard tracking and risk resolution should be included in the SSPP. 

The system safety requirements paragraph discusses program objectives, general design requirements, the system safety precedence (safety precedence sequence), and risk assessment descriptions of both severity and probability categories (Tables 3-1 and 3-2). 

The prioritized list of controls for hazards may be called the safety precedence sequence, the hazard reduction precedence, the hazard control sequence, the system safety sequence, or any of several other terms. The only real difference between an operating hazard analysis (OHA) and an operating and support hazard analysis (O SHA) is the name. 

Hazard control involves applying the safety precedence sequence to identified hazards that present unacceptable risks until the risks are controlled to an acceptable level. Inherent in the analysis and control process is verification... 

Another means of improving overall system reliability is by application of the system safety precedence (or safety precedence sequence or hazard reduction precedence sequence). 

List the steps in the system safety precedence sequence. 

Energy control provisions Were the safest forms of energy used, consistent with operational requirements Were adequate barriers provided Was the safety precedence sequence properly applied Were energy flows carefully considered and routed away from vulnerable targets where possible ... 

The safety precedence sequence is a method of reviewing safety options. Clearly, the most effective option to reduce hazards is to ehminate them altogether. This is rarely possible. Most options are controlled cost, technical capabihty and informatioa As we select options lower down the sequence, the controls become less rehable and less effective. In most cases, some compromise has to be reached in order for work to continue. 

Hazards, and the risks they present, can be prioritized and control measures adopted based on the safety precedence sequence (see Chapter 1) or the hierarchy of controls (see Chapter 2). 

Risk control status is achieved through field observations, regular and independent inspections, statistical analysis and in discussion with all levels of the workforce. The task is to ensure, as accurately as possible, that the barriers in place to control hazards are appropriate and effective. The safety precedence sequence mentioned in Chapter 1 is useful as a guide in establishing the adequacy of risk control strategies ... 

It is necessary to be aware that some corrective measures are better able to produce the desired results than others, and that some are very ineffective indeed as controls. The safety precedence sequence shows the order of effectiveness of measures ... 

---