What Does Self-Reactive Chemical Mean?
Self-reactive chemicals are thermally unstable liquid or solid chemicals that can undergo exothermic decomposition without interacting with oxygen.
Self-reactive chemicals can start decomposing due to:
- Contact with acids
- Contact with heavy metal compounds
- Contact with bases
Safeopedia Explains Self-Reactive Chemical
The Occupational Safety and Health Administration’s (OSHA) Hazard Communication Standard (HCS) defines self-reactive chemicals as:
"thermally unstable liquid or solid chemicals liable to undergo a strongly exothermic decomposition even without the participation of oxygen (air). This definition excludes chemicals classified as explosives, organic peroxides, oxidizing liquids, or oxidizing solids."
Self-Reacting Chemical Classifications
This classification considers self-reactive chemicals other than those classified as explosives, organic peroxides, oxidizing solid or liquid except the mixture contains 5% or more of combustible organic substances, with the heat of decomposition less than 300 J/g, or having self-accelerating decomposition temperature (SADT) greater than 75°C (167°F) for a 50 kg package.
The classifiation criteria for self-reacting chemicals is as follows:
Self-Reactive Type A
Can detonate or deflagrate rapidly, as packaged.
Self-Reactive Type B
Possessing explosive properties and which, as packaged, neither detonates nor deflagrates rapidly, but is liable to undergo a thermal explosion in that package.
Self-Reactive Type C
Possessing explosive properties when the chemical as packaged cannot detonate or deflagrate rapidly or undergo a thermal explosion.
Self-Reactive Type D
Meets one of the following criteria in laboratory testing:
- Detonates partially, does not deflagrate rapidly, and shows no violent effect when heated under confinement
- Does not detonate at all, deflagrates slowly, and shows no violent effect when heated under confinement
- Does not detonate or deflagrate at all, and shows a medium effect when heated under confinement
Self-Reactive Type E
In laboratory testing, it neither detonates nor deflagrates at all and shows low or no effect when heated under confinement.
Self-Reactive Type F
In laboratory testing, it neither detonates in the cavitated state nor deflagrates at all and shows only a low or no effect when heated under confinement, as well as low or no explosive power.
Self-Reactive Type G
In laboratory testing, it neither detonates in the cavitated state nor deflagrates at all and shows no effect when heated under confinement nor any explosive power, provided it is thermally stable.
Self-Reactive Chemical Hazards
The primary hazards associated with self-reactive chemicals are fire and explosion. The explosion hazard associated with some of these chemicals ranges from thermal explosion to deflagration or detonation.
Some self-reactive chemicals can be dangerously reactive and can decompose when exposed to sunlight, heat, friction, or shock. Azo compounds may have an SADT or a temperature below which storage can be hazardous. Some of these chemicals gradually decompose giving off gas, while some may crystallize below certain temperatures, concentrating them.
Mitigating Self-Reactive Chemical Risks
- Follow safe chemical handling practices
- Observe all specific safety procedures established for the facility or jobsite
- Wear appropriate personal protective equipment (PPE)
- Keep the amount of self-reactive chemical on hand to a minimum
- Select the most stable self-reactive chemical suitable for the job
- Opt for self-reactive chemicals that contain stabilizing diluents or inhibitors