Environmental, Health and Safety Services

Piranha Solution

Typically, there are two different piranha solutions used in the laboratory.

  • Acid piranha is a 3:1 mixture of concentrated sulfuric acid (H2SO4) with hydrogen peroxide (H2O2). It produces heat upon mixing and is self-starting, meaning it will react with organics without being heated.
  • Base piranha is a 3:1 mixture of ammonium hydroxide (NH4OH) with hydrogen peroxide (H2O2). It is equally dangerous as acid piranha when hot, although the base piranha must be heated to 60°C before the reaction takes off.

It is possible for the piranha reaction to accelerate out of control. The results could be as small as an overflowing container and a bench top to clean up, or as large as a major laboratory explosion. Most often, these out of control reactions are caused by the addition of organic compounds to piranha solutions. The rapid oxidation of these organic materials produces enormous quantities of heat and gas. In a closed container, this will lead to an explosion.

The handling of piranha solutions requires the use of personal protective equipment, such as safety goggles AND a full face shield, heavy-duty rubber gloves (or equivalent), and a protective apron over a lab coat.

It is imperative that safety equipment contaminated with organic material not come into contact with piranha solution. Remember, the addition of organics to fresh hot piranha solution produces an immediate and violent reaction.

  • It is imperative that the worker remembers that he or she IS organic.  Piranha solution on a person will produce an immediate and violent reaction. Avoid all skin exposures in the presence of piranha solutions.

Piranha can melt or otherwise attack plastic containers. Use only glass containers for piranha solution. All containers having piranha solution, including hazardous waste containers, must be clearly labeled as containing piranha solution. The label must also detail the hazards (corrosive, reactive) and be clearly visible to anyone working with or coming into contact with the material.

  • When preparing the piranha solution, always add the peroxide to the acid very slowly.  The peroxide is added immediately before the process because it immediately produces an energetic exothermic reaction with gas release.  Remember, piranha solutions will heat up during the mixing process.  The solution is likely to become very hot, over 100°C – handle with care.
  • Substrates and glassware that is being cleaned should be rinsed and dried before placing them in a piranha bath.  Piranha solution is used to remove organic residues, not the organic compounds themselves.
  • Leave the hot piranha solution in an open container until cool.  Don’t store hot piranha solutions because closed containers will likely explode.
  • Adding any acids or bases to piranha, or even adding water, will accelerate the reaction, producing more heat, gas, and potential for accidents.
  • Mixing piranha with organic compounds may cause an explosion.  This includes acetone, photo resist, isopropyl alcohol, and nylon.  It is imperative that organics are not stored or staged near the piranha solution mixing area or the bath.
  • Do not attempt to store hot piranha solution in an air-tight container – it will explode.  Leave the solution in an open container and allow to cool down several hours.  Make sure that the open container is clearly labeled and left in a safe area during this process.
  • Once cooled down, the solution can be transferred to a closed, glass container for waste storage.  Clearly label the container with “Hazardous Waste – Piranha Solution”.  No other materials must be mixed with this waste!
  • In case of exposure to piranha solution, such as skin or eyes, rinse the affected area thoroughly with large amounts of water (safety shower or eye wash station) for 15 minutes or more to reduce the likelihood of burns.  Remove all contaminated clothing immediately with appropriate gloves and safely discard.
  • In case of exposure to piranha solution from inhalation, the person should be assisted to an area with fresh, uncontaminated air.  Seek medical attention in the event of respiratory irritation, cough, or tightness in the chest.  Symptoms may be delayed.