The Structured What-If Analysis (SWIFT) technique is simple to use and has been effectively applied to a variety of large scale processes. It can be useful with mechanical systems such as production machines, with simple task analysis such as assembly jobs, as well as with reviewing tasks in chemical processing. No specialized tools or techniques are needed. Individuals with little hazard analysis training can participate in a full and meaningful way. It can be applied at any time of interest such as during construction, during debugging, during operations, or during maintenance. The results of the analysis are immediately available and usually can be applied quickly. This is especially true if the review team members also operate or maintain the system being assessed.

The technique uses a structure brainstorming technique to determine what can go wrong in specific scenarios and identify the likelihood and the resulting consequences. It relies heavily on the experience and intuition of the review team. It is somewhat more subjective than other methods, such as Hazard and Operability Analysis (HAZOP), which require a more formal and systematized approach. If all of the appropriate What-If questions are not asked, this technique can be incomplete and miss some hazard potentials. It may be appropriate to assign those more dangerous portions of the system to a more rigorous review such as HAZOP. A SWIFT analysis can address potential equipment failures and human errors and can point out the potentials for safety and health improvements; however, it is also an opportunity to minimize operating and quality problems.  


This technique requires minimal amount of formal training; however; it does require someone to be familiar with the equipment, processes, etc. It typically takes a skilled and strong facilitator to keep the discussions on track, and ensure that all the questions are asked, and addressed. An operating procedure and/or Piping and Instrument Diagram (P&ID) is helpful to keep the process on track.


At each step in the procedure or process, What-If questions are asked and answers generated. To minimize the chances that potential problems are not overlooked, moving to recommendations is held until all of the potential hazards are identified.


  • Simple research applications
  • Complex processes
  • Research environment, where teaching is the core mission
  • Assessing existing processes and experiments

As the “What-If” questions are being generated, the facilitator should ensure that each member of the team has an opportunity to input potential errors or failures. Determining the answer to each question as it is generated creates the danger of closing too soon on all possible upsets. The facilitator needs to assess if the team has really looked at all of the possibilities before going to the next step of answering the questions. Break up the analysis into smaller pieces if there is danger of just developing questions and not gaining the value of having them fresh in mind to answer those questions.

Failure to ask the right questions is one of the shortcomings of a What-if Analysis. Experienced personnel are knowledgeable of past failures and likely sources of errors and is therefore very important during this analysis. Their experience should be used to generate relevant “What-If” questions. Using the process and equipment documents and drawings/PID’s available and knowledge of the review team, “What-If” questions can be formulated around human errors, process upsets, and equipment failures. These errors and failures can be considered during normal production operations, during construction, during maintenance activities, as well as during de-bugging situations. The list below are some examples of scenarios that could be addressed

  • Procedures followed incorrectly or not followed at all
  • Procedures incorrect or latest procedures not used
  • Operator inattentive or not adequately trained
  • Procedures modified due to upset
  • Process conditions upsets
  • Equipment failure
  • Miscalibrated instrumentation
  • De-bugging errors
  • Utility failures such as power, steam, gas, vacuum
  • External influences such as weather, vandalism, fire
  • Outside malicious interference
  • Combination of events such as multiple equipment failures

Following is a list of sample What-if questions from the ACS website: to get your group thinking in the right directions. These questions can be modified according to experiment or process, biological agents etc.


Human errors occur regardless of training and experience. Human error factors may drive consideration of written SOPs, a decision for engineering controls, etc.

  • What if material used is too concentrated (or diluted)?
  • What if the valve/stopcock does not open (or close)?
  • What if the valve(s) are opened (or closed) in the wrong sequence?
  • What if inert gas is omitted?
  • What if unintended materials are mixed together?
  • What if readings are missed or ignored?
  • What if warnings are missed or ignored?
  • What if there are errors in diagnosis?


The following questions concern utilities, which are key to the support of any experiment or process:

  • What if power is lost?
    Consider: Automatic shutoffs and emergency power
  • What if power is restored automatically after loss?
    Consider: Manual restarts
  • What if laboratory ventilation is lost?
    Consider: Automatic shutoffs, emergency power, and redundant mechanical exhaust fans


Consideration of failure of materials or components may result in decisions for additional controls or changes to higher rated or alternative types of materials and components.

  • What if there’s unexpected over-pressurization?
    Consider: Pressure relief devices and barriers; personal protective equipment (PPE)
  • What if glassware breaks during reaction?
    Consider:Spill control; PPE
  • What if there’s a failure of equipment cooling?
    Consider:Alarms, automatic shutoffs, and emergency shut-off procedures


This should be included since, despite best efforts with hazard reviews and training, incidents will occur.

  • What if a body is impacted by liquids or solids?
    Consider:Physical barriers
  • What if someone is exposed to vapors or gases?
    Consider: PPE; ventilation
  • What if someone is exposed to respirable particles?
    Consider: Use of wet contamination control methods, ventilation controls, and respiratory protection


After being assured that the review team has exhausted the most credible “What-If” scenarios, then the team begins to analyze the consequences.


  • Ask What-If ….
  • Note the answers and the likelihood and consequences.
  • Evaluate if these are acceptable or not (wait with suggested recommendations)
  • Use an operating procedure and/or Piping and Instrument Diagram (P&ID), as the basis for the brainstorming
  • At the end of the brainstorming review the table and begin to discuss and list recommendations in preferred order
  • Submit to leadership for final decision of what mitigation measures that are to be included in the project
  • Assign responsibilities and milestones for implementation

 “What-If” questions can be formulated around human errors, process upsets, and equipment failures.  These errors and failures can be considered during normal production operations, unanticipated shut down due to power failure or similar, during construction, during maintenance activities, etc. It can be helpful to review past accident/incident and near-misses logs and root cause analyses. For example:

  • Failure to follow procedures or procedures followed incorrectly
  • Incorrect or out of date procedures
  • Operator inattentiveness or lack of training
  • Equipment failures
  • Lack of calibration
  • Utility failures such as power, steam, gas
  • External influences such as weather, vandalism, fire
  • Combination of events such as multiple equipment failures

The risk assessment should be done as efficiently and early as possible during the design project, and risk mitigation strategies should likewise be implemented in the programming phase as soon as possible in order to provide a safe environment for all personnel groups involved. However, the team should consider employing an independent, third-party risk assessment that documents and evaluates as many perspectives and ideas as possible.


If you want to read more, the references for some of the text above is: Handbook of Occupational Safety and Health, Second Edition, edited by Lou Diberardinis, “Chapter 6 Risk Assessment Techniques,” Thomas M. Dougherty, pp. 127-178, John Wiley and Sons, 1999 as well as and