An anhydrous hydrogen fluoride (AHF) lecture bottle spontaneously exploded in a laboratory. No one was injured, but the lab was extensively damaged. The lecture bottle had split along its seam. Its cap and valve assembly were located to the immediate left.
Cause
The explosion was caused by hydrogen gas pressure build up in the cylinder. AHF comes in carbon steel cylinders as a liquefied gas under a pressure of 0.9 psi at 70 oF (i.e., the vapor pressure of the liquid). Though cylinders should be passivated with fluorine, which forms a protective coating, over time AHF may slowly react with the iron in a cylinder to form iron fluoride and hydrogen gas. The generation of hydrogen gas may produce cylinder pressures as high as several hundred psi.
Recommended Actions:
- The recommended safe storage time for AHF is two years. Contact the vendor for pick up and disposal for cylinders more than two years old. (Unused gas should also be returned, even if it has been less than two years since it was obtained.)
- If the cylinder is less than two years old and there is a desire to keep it, then: Check the pressure of the cylinder. It must be within the maximum pressure stamped on the neck of the bottle. If the pressure is at or above the cylinder's maximum pressure, contact the vendor for pick up and disposal. Do not attempt to move the cylinder yourself.
If below the cylinder's maximum pressure, vent excess pressure through an appropriate medium. Use a two-person team. Conduct venting in a fume hood. Control all ignition sources during venting, since most of the vent gas will be H2. At a minimum, wear chemical goggles, nitrile gloves, and a lab coat for protection against gaseous HF. Keep an HF exposure kit on hand. An eyewash and safety shower must be readily accessible (within a ten-second travel distance). Any skin, eye or respiratory irritation may be indicative of a possible exposure. Follow the first aid procedures listed on the exposure kit.