Incident Insights: Hazardous energy leads to a fan belt injury


On January 31, 2022, a UW employee was assigned to replace the motor-pulley V-belts on a supply air fan that was part of a multiple fan system. The maintenance worker turned off the electricity to the supply fan motor and removed the V-belt guard to gain better visibility of the belts. The fan stopped, but airflow from the other supply fans on the system caused the supply fan, under repair, to move in the reverse direction. The worker placed their gloved hand on the moving belts to stop the movement, and their hand was pulled into the belt and pulley system. As a result, the worker received lacerations on their hand and is receiving physical therapy to gain full use of their hand.

Root-causes and contributing factors

The root-cause of this incident was the source of hazardous energy created by the reverse movement of the fan energized by negative air pressure from the other fans on the system (called “windmilling”), which was not identified and isolated prior to starting work.

  • The mechanical hazard associated with the potential rotating fan, belt and pulleys associated with “windmilling,” had not been isolated and/or blocked to prevent movement of the fan and components.
  • The guard (to protect workers from moving parts) was removed without first verifying that zero hazardous energy existed in the system.
  • Lack of written equipment-specific energy control procedures for this maintenance activity.

How to prevent future incidents

  1. Conduct pre-task planning; develop a job hazard analysis or hazard review prior to performing work.
  2. When servicing or repairing equipment or systems, a specific energy control procedure is required to be documented prior to work being performed.
    1. It is important to identify all energy sources that need to be isolated by reviewing drawings, schematics, and/or equipment manuals for each distinct scope of work. A walk-down of the equipment and system is recommended.
    2. Download a hazardous energy control procedure form from the Hazardous Energy Control – Lockout/Tagout (LOTO) webpage on the EH&S website.
    3. Complete the hazardous energy control procedure form prior to starting work. The form must include the following information:
      • Scope of work to be performed
      • Affected personnel who will be notified that the equipment or system will be de-energized
      • Steps for shutdown of equipment (note if sequence is important)
      • Type and magnitude of energy of each hazardous energy source
      • Energy-isolating devices (EIDs) for isolating each hazardous energy source (tag #, Circuit Breaker#, etc.)
      • Procedures for releasing any stored or residual energy for each hazardous energy source, if applicable
      • Record application of lockout or tagout on energy sources by each person
      • Method for verifying zero energy for each hazardous energy source
      • Record removing lockout/tagout devices and re-energizing machine or equipment
  3. Make sure that you have been trained in LOTO and on the equipment that you are using and/or maintaining.
  4. Conduct an annual audit of the specific equipment hazardous energy control procedures and assessment of personnel performing LOTO on equipment or systems.
  5. Instruct workers to never place hands or any part of the body in proximity to moving parts or unguarded machinery.
  6. Report all accidents and near-miss incidents using the UW’s Online Accident Reporting System (OARS) within 24 hours.

We are sharing this information to support our continuing effort to promote a culture of safety and to prevent future serious incidents. Please share this alert with anyone you think would benefit from this information.

For more information, please contact EH&S’s Occupational Safety & Health Team at 206.543.7388 or