Reactive chemicals are substances that can undergo uncontrolled reactions, alone or when mixed, heated or exposed to air or water, releasing heat, gas or pressure that can cause fires, explosions or toxic releases.
Reactive chemicals are substances that can undergo a hazardous chemical reaction, either on their own or when they contact other materials, air, water, heat or shock. The reaction can release large amounts of heat, gas or pressure very quickly, leading to fires, explosions, ruptured vessels or toxic gas releases.
Reactivity hazards come in two broad forms. Some chemicals are unstable and can decompose, polymerize or react with themselves. Others are dangerous because of what they react with, such as water, air or incompatible chemicals. A runaway reaction happens when a reaction generates heat faster than it can be removed, so the temperature and reaction rate keep climbing.
The U.S. Chemical Safety and Hazard Investigation Board (CSB) studied 167 serious reactive incidents that occurred in the United States between 1980 and 2001. Those incidents caused 108 deaths, and fewer than half involved chemicals covered by OSHA's Process Safety Management standard or EPA's Risk Management Program rule.
Many reactive incidents involve chemicals that are reasonably stable alone but react when mixed. Common examples include acids mixed with bases, bleach mixed with acids or ammonia, and oxidizers mixed with fuels or organic materials.
Under OSHA's Hazard Communication standard, 29 CFR 1910.1200, chemicals are classified using GHS-based physical hazard classes that include self-reactive substances, organic peroxides, pyrophoric and self-heating substances, substances that emit flammable gas in contact with water, and oxidizers. Section 10 of the safety data sheet, "Stability and reactivity," lists conditions to avoid, incompatible materials and hazardous decomposition products.
The NFPA 704 diamond uses the yellow section to rate instability from 0 to 4. A W with a line through it in the bottom section warns of unusual reactivity with water.
Where chemicals are processed, not just stored, data sheets are not enough. Reaction calorimetry and thermal stability testing show how much heat a reaction releases, how fast, and at what temperature a runaway could start.
On December 19, 2007, a reactor at T2 Laboratories in Jacksonville, Florida, burst and exploded while the company was producing a gasoline additive. The CSB found that a runaway exothermic reaction occurred during the process and that insufficient cooling was the only credible cause it identified. Four people were killed and 32 were injured, including members of the public at nearby businesses.
The CSB concluded that T2 did not recognize the runaway reaction hazard of the chemical it was producing. The cooling system lacked design redundancy and the pressure relief system could not handle a runaway reaction. The board also noted that reactivity hazard awareness was not a basic part of chemical engineering education, which is why reactive chemical training and testing are now emphasized across the industry.
A flammable liquid burns when its vapor meets an ignition source and air. A reactive chemical can release energy through a chemical reaction that does not need an outside ignition source, such as decomposition, polymerization or a reaction with water.
Only some. PSM applies to listed highly hazardous chemicals above threshold quantities and to certain flammables. The CSB found that more than half of the reactive incidents it studied involved chemicals not covered by PSM or EPA's Risk Management Program.
Start with Section 10 of the safety data sheet and the hazard classes on the label. For process work, use testing data and a qualified chemist or process safety engineer.
A runaway reaction occurs when a reaction produces heat faster than the system can remove it. The temperature rises, the reaction speeds up, and pressure can build until a vessel fails.
Store them according to the SDS, separated from incompatible materials, at the right temperature, away from water if they are water-reactive, and with dates tracked for materials that can degrade or form peroxides.
Part of SafetyIQ's EHS glossary: plain-English definitions of workplace health and safety terms.
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