IEC Category Ratings: Use the Right Tools for the Job


Using the proper tools for the job can help keep electrical workers safe. For example, insulated tools can help prevent an arc flash incident. In fact, test tools are some of the most important personal protective equipment (PPE) items electrical workers can use.

Forensic investigations have determined that sometimes inferior test equipment—without an IEC category rating or with a rating that does not match the task—can actually explode if used improperly.

The 2012 Edition of NFPA 70E references the ANSI IEC 61010-1 standard that defines test tool category ratings. The following partial list describes the IEC category ratings:

  • CAT I — Protected electronic equipment.
  • CAT II — Single-phase receptacle-connected loads such as appliances and portable tools.
  • CAT III — 3-phase distribution including single-phase commercial lighting and equipment in fixed locations such as switchgear and polyphase motors.
  • CAT IV — 3-phase at the utility connection, outdoor conductors, electricity meters, and service entrances.

It's important to note that CAT ratings as marked on test and measurement equipment have no relation to the PPE Hazard Risk Categories listed in NFPA 70E.