Texas Tech University

Improper handling of nitric acid waste damages a cabinet and scatters glass shards throughout laboratory – October 2011

What happened?

Graduate students were performing a procedure they had used successfully in the past. The procedure used four materials: nitric acid, hydrofluoric acid, hydrochloric acid and peroxide, and hydrofluoric acid with ethanol. At the end of the procedure, they disposed of each material in a separate waste bottle in a cabinet beneath the hood.

Several hours after the procedure ended, after the students had left the lab, a waste bottle exploded. The blast blew open the doors to the cabinet and propelled 0.5 inch glass shards about 35 feet over the length and breadth of the lab. No one was in the lab, and there were no injuries. The Lubbock Fire Department (LFD) and HAZMAT team responded and cleaned up the laboratory.

 

Area where incident occurred before LFD HAZMAT team cleanup.

Area where incident occurred before LFD HAZMAT team cleanup.

One of two 500 ml bottles of nitric acid that were broken.

One of two 500 ml bottles of nitric acid that were broken.

Two 500ml bottles of Hydrofluoric acid that were punctured.

Two 500 ml bottles of hydrofluoric acid that were punctured.

Red dots on floor indicate glass shards at end of lab farthest from explosion in hood.

Red dots on floor indicate glass shards at the end of the lab farthest from explosion in the hood.

What was the cause?

The explosion was likely caused by a reaction between nitric acid and ethanol, created when nitric acid waste was mixed with the hydrofluoric acid + ethanol waste. These wastes were mixed in a glass bottle, the expected oxidative reaction occurred, pressure built up, and the bottle exploded. This is the reaction expected when nitric acid is combined with organics – no surprises at all.

Why did the wastes get mixed together? Likely reasons:

What corrective actions were taken?

EH&S closed the laboratory, reviewed chemical storage and waste handling procedures with the students and PIs, and retrained laboratory personnel in appropriate handling, storage, and waste procedures for nitric acid.

Extensive guidance about waste handling was provided to the TTU community via e-mails and a website story about hazardous waste procedures:

How can we prevent incidents like this?

Resources

  1. Bretherick’s Handbook of Reactive Chemical Hazards, 6th Edition, P.G. Urben, ed., 1999
  2. Prudents Practices in the Laboratory, Handling and Management of Chemical Hazards, National Research Council, 2011