Accidental Mixing of Bleach and Acid

What was the cause?

The cause of the accident was a momentary period of inattention and a poorly labeled tub, with the experienced researcher expecting a white tub to contain a bleach solution and not to contain HCl. Glassware soaking tubs can contain solutions with detergent, bleach, caustic bath, or (less frequently) an acid bath. The acid bath in this case was not clearly labeled; there was only a small piece of tape with "5%HCl" on the lid. There was no label on the actual container.

What corrective action was taken?

This incident impressed upon the lab how important it is to have all containers of chemicals clearly labeled with the contents. It is also important to label the primary hazard of any chemical mixture. In this case the acid bath should have been labeled as containing "5% hydrochloric acid, corrosive". After this incident, the lab properly labeled all their chemical containers, even containers of water.

In the future they plan to use physically different containers or tubs so the bleach and acid baths are not confused again. Normally, the acid bath is used in an orange bucket and the bleach bath in the white square tub. If your lab has acid and bleach baths, EH&S suggests that you use very different looking containers, but always clearly label the container (not just the lid) with the contents and hazard.

There were previously written standard operating procedures (SOP) on how to work with the bleach and acid baths. The procedures described what types of protective equipment must be worn and what to do if there is an accidental spill; however, the procedures were hidden and dusty, so they were re-posted and discussed in a group meeting.

How can incidents like this be prevented?

• Clearly label all chemical containers with the chemical's name and hazards.

• Use physically different containers for bleach and acid baths.
• Emphasize the hazard of accidentally mixing acid and bleach. If your lab has acid or bleach baths discuss this incident in your lab group meeting. Document the training.
• For work with acids, bases, or bleach, have a written SOP that includes protective clothing and emergency procedures for an accident. There should be an eyewash and safety shower if acid or bleach is being handled.
• Consider placing the acid baths inside fume hoods to contain any acid vapors or hazardous gases that might be produced. The fume hood sash can also be used as a splash shield.