Build-up of
Dangerous Perchloric Acid Salts Due to Lack of a Hood
Preventive Maintenance Program
Identifier: Laboratory
Safety Incidents (American Industrial Hygiene Association)
At an unnamed University in 2002, it was
discovered that a perchloric acid fume hood was heavily contaminated with
potentially explosive perchloric acid salts.
Due to a malfunction in the wash-down system,
only the interior of the hood was subjected to a water spray. The duct from the
top of the hood to the stack on the roof had not been washed down for an
undetermined length of time while perchloric acid continued to be heated in the
hood.
As a result, perchloric acid salts formed on many
locations along the length of the duct, particularly where the stainless steel
welds were made.
Although only visible on the outside, it was
presumed contamination was worse on the interior of the stainless duct.
Of special concern would be organic materials
being contaminated with perchloric acid.
These materials can become flammable and/or explosive with heat or
friction. As a result of the non-functional wash-down system, the fan located
on the roof was completely destroyed by the acid.
Non-functional
wash-down system Destroyed
fan
Analysis of Lessons Learned:
To prevent this type of situation when working with perchloric acid, any user of perchloric acid must:
1. Review the existing SOP for use of perchloric acid [SOP for Non-Heated Perchloric Acid <70% (available from EH&S)]
2. Provide training for all employees
3. REMEMBER:
o Never heat perchloric acid in a chemical hood unless the hood has been designed for use with perchloric acid and has a functioning wash-down system.
o If your protocol requires solutions of perchloric acid above 70% and/or heating of perchloric acid, contact EH&S for guidance on the development of a High-Hazard SOP.
4. Always store acids separately from organic solvents.