Article by Ahmed Elsotouhy

Peroxide-forming chemicals are common in academic research laboratories and are often used without incident for years. However, when these materials are stored too long, concentrated, or improperly disposed of, they can quietly become one of the most serious explosion hazards in the research environment. Solvents such as diethyl ether and tetrahydrofuran (THF), as well as unintentionally formed organic peroxides, can accumulate shock-sensitive compounds that pose significant risk to researchers, facilities, and operations.

A review of peroxide-related laboratory incidents at universities over the past several decades shows a clear pattern: most accidents did not occur during complex experiments, but during routine activities like laboratory clean-outs, rotary evaporation, or hazardous waste handling. In several well-documented cases, aged solvents that had not been tested for peroxides detonated when containers were opened, concentrated, or discarded. In others, peroxide residues in “empty” bottles exploded when handled as ordinary glass waste. These incidents highlight that peroxide hazards are not theoretical—they are predictable and repeatable when controls fail.

Major University Peroxide Incidents

• UCSF (1995): Ten-year-old diethyl ether containers exploded during a laboratory clean-out, shattering windows.
  Cause: Long-term storage and high peroxide accumulation.
• UC Berkeley (2006): Unstabilized THF (>100 mg/L peroxides) detonated during rotary evaporation, injuring a student.
  Cause: Concentration of peroxide crystals during near-dry evaporation.
• University of Minnesota (2017): An “empty” solvent bottle containing dry peroxide crystals exploded when discarded.
  Cause: Shock-sensitive peroxide residues in an untreated container.
• University of Bristol (2017): Approximately 30–40 g of TATP formed unintentionally during an acetone/hydrogen peroxide reaction; a controlled detonation was required.
  Cause: Unintended peroxide byproduct and insufficient hazard mitigation.
• Hong Kong Laboratory (2016): Expired hydrogen peroxide decomposed violently when poured into a metal waste drum, injuring eight individuals.
  Cause: Incompatible container and degraded oxidizer.

Peroxide-Forming Chemicals: What Goes Wrong—and How to Prevent It

Common Failure Modes

• Long-term storage of ethers and THF
• Lack of container dating or routine peroxide testing
• Evaporation or distillation to near-dryness
• Disposal of untreated “empty” containers
• Inadequate assessment of unintended peroxide-forming reaction pathways

Prevention Essentials

• Date all peroxide-forming chemicals and enforce strict expiration timelines
• Test for peroxides before evaporation, distillation, or disposal
• Store materials in cool, dark locations and minimize quantities on hand
• Treat “empty” containers as hazardous; avoid metal containers for oxidizers
• Provide regular, peroxide-specific safety training
• Require PI and EHS review of aging or high-risk peroxide-forming chemicals

Root Causes and Prevention

Across institutions, common root causes emerge. Prolonged storage of peroxide-forming chemicals, lack of routine peroxide testing, underestimation of risks associated with near-dry evaporation, and improper disposal practices were present in nearly every documented incident. Importantly, these hazards were already well documented in safety literature, underscoring that the issue is not a lack of knowledge, but inconsistent application of best practices across the chemical lifecycle.

Preventing peroxide incidents starts with strong inventory management: dating containers upon receipt and opening, limiting storage time, and removing aged materials before they become dangerous. Peroxide testing should be performed before evaporation, distillation, or disposal, and “empty” containers must be treated as potentially hazardous until verified safe. Just as critical is ongoing training—for students, staff, and faculty—so that peroxide risks remain visible even when experiments become routine.

Faculty and principal investigators play a central role in this process by setting expectations for safe solvent handling, prohibiting near-dry evaporation without verification, and prioritizing laboratory clean-outs during personnel transitions or lab closures. From an EHS perspective, peroxide hazards should be explicitly addressed in inspections, waste procedures, Chemical Hygiene Plans, and safety training programs, using real incident examples to reinforce why these requirements matter.

To support these efforts, MU Environmental Health & Safety is happy to provide peroxide-forming chemical test strips to laboratories, including a starter kit with instructions for use and reordering. This service is intended to make routine peroxide testing easy, accessible, and consistent across campus.

Peroxide-forming chemical incidents are preventable when vigilance, testing, and oversight are consistently applied. By managing these materials from procurement through disposal—and by learning from past incidents—we can protect our researchers and facilities while strengthening our shared safety culture. By working Safer Together, we help ensure that innovation and discovery continue without unnecessary risk.