GHS / HazCom term · Glossary
Self-Reactive Substance
Verified vs OSHA sources · 2026-10-05
A GHS/HazCom physical hazard class (Appendix B.8 of 29 CFR 1910.1200) covering thermally unstable liquid or solid chemicals liable to undergo a strongly exothermic decomposition even without the participation of oxygen (air). Self-reactive substances are sorted into seven types, A through G, by how violently they react when heated or confined: Type A can detonate or deflagrate rapidly as packaged, while Type G is thermally stable and shows no hazardous reaction. Types with explosive or fire properties carry the GHS01 (exploding bomb) and/or GHS02 (flame) pictogram.
Also known as: self-reactive chemical, self-reactive material, GHS self-reactive class
Self-Reactive Substance at a glance
- Defined in 29 CFR 1910.1200 Appendix B.8 — thermally unstable, self-decomposing without oxygen.
- Seven types, A through G, graded by decomposition/explosion behavior under heat and confinement.
- Type A: can detonate or deflagrate rapidly as packaged; Type B: has explosive properties and may thermally explode in the package.
- Types C–F: progressively lower explosive/deflagration severity; Type G: thermally stable, not classified for self-reactive labeling.
- Controlled by SADT (Self-Accelerating Decomposition Temperature) — many require temperature control during storage/transport.
- Pictograms: GHS01 (exploding bomb) for Types A/B; GHS02 (flame) for Types B–F; Type G carries no self-reactive label.
- Explicitly EXCLUDES chemicals already classified as explosives, organic peroxides, or oxidizers.
In plain English
A chemical that can decompose violently on its own when it gets too warm — no oxygen or spark needed. Because the reaction is strongly exothermic (heat-releasing), it can feed itself and run away. GHS grades them from Type A (can detonate in its package) down to Type G (stable enough that it isn't a labeling concern). They behave a lot like organic peroxides, which are a closely related class.
What the source says, in summary
Self-reactive chemicals are thermally unstable liquid or solid chemicals liable to undergo a strongly exothermic decomposition even without participation of oxygen (air). This definition excludes chemicals classified under this Appendix as explosives, organic peroxides, oxidizing liquids or oxidizing solids.
In context
A classification or labeling concept from the UN Globally Harmonized System, adopted into US law through OSHA's Hazard Communication Standard (29 CFR 1910.1200) and its appendices.
Where this is written in OSHA's rules
- 29 CFR 1910.1200 App B.8Read on eCFR / OSHA.gov
- 29 CFR 1910.1200Read on eCFR / OSHA.gov
Example
A specialty chemical decomposes exothermically when warmed, and testing shows it has explosive properties but will not detonate or deflagrate rapidly in its packaging — behavior matching Type C. It is classified as a self-reactive substance Type C, labeled with the GHS02 flame pictogram and the signal word 'Danger,' and its SDS specifies a control temperature and emergency temperature based on its SADT. During shipping it must be kept below the control temperature, because allowing it to self-heat toward its SADT could trigger a runaway decomposition.
Why it matters
Self-reactive substances cause fires and explosions without any external ignition source or oxygen — a runaway decomposition can start simply because the material got too warm in storage or transit. That makes temperature control (SADT-based) and correct type classification safety-critical. Because self-reactives overlap with explosives and organic peroxides, mislabeling one as an inert chemical removes exactly the temperature-control and handling warnings that prevent a thermal runaway.
Self-reactive vs. organic peroxide vs. self-heating
All three involve a substance reacting on its own, but the mechanism differs. A SELF-REACTIVE substance (B.8) is thermally unstable and decomposes exothermically without oxygen, driven by heat. An ORGANIC PEROXIDE (B.15) is a specific structural family (containing the –O–O– bivalent peroxide group) that is essentially a self-reactive substance defined by chemistry rather than test behavior — it uses the same Type A–G scheme. A SELF-HEATING substance (B.11), by contrast, reacts slowly WITH oxygen in air and only ignites in large quantities over long periods — it needs air, whereas self-reactives and peroxides do not. GHS deliberately classifies organic peroxides separately even though they are chemically a subset of self-reactive behavior.
Self-Reactive Substance Types (29 CFR 1910.1200 App B.8)
| Type | Behavior |
|---|---|
| A | Can detonate or deflagrate rapidly as packaged |
| B | Has explosive properties; may thermally explode in the package |
| C / D | Explosive properties present, but cannot detonate; partial/slow deflagration |
| E / F | Low or no explosive power; low or no effect when heated under confinement |
| G | Thermally stable (SADT 60–75°C); no hazardous reaction — not labeled self-reactive |
Self-Reactive Substance: frequently asked questions
- What is a self-reactive substance?
- It is a thermally unstable liquid or solid chemical that can undergo a strongly exothermic (heat-releasing) decomposition even without oxygen from the air. Because the decomposition releases heat, it can accelerate and run away once the material warms past a critical point. GHS classifies self-reactive substances into seven types (A–G) based on how violently they react under heat and confinement, and many require temperature-controlled storage.
- What do the self-reactive Types A through G mean?
- The types grade decreasing severity. Type A can detonate or deflagrate rapidly in its package; Type B has explosive properties and may thermally explode when packaged; Types C and D have explosive properties but cannot detonate and deflagrate more slowly; Types E and F show low or no explosive power; and Type G is thermally stable with no hazardous reaction and is not labeled as self-reactive. The type determines the pictograms, signal word, and whether temperature control is required.
- How is a self-reactive substance different from an organic peroxide?
- Chemically, organic peroxides are a subset of self-reactive behavior — but GHS classifies them separately. An organic peroxide is defined structurally by its –O–O– peroxide bond, whereas a self-reactive substance is defined by its thermal decomposition test behavior. Both use the same Type A–G scheme and both are temperature-sensitive. The self-reactive class explicitly excludes chemicals already classified as organic peroxides, explosives, or oxidizers.
Related terms
Free tools for this
Governing OSHA standards
More GHS terms
A GHS health-hazard class for the harmful effects that follow a single dose, several doses within 24 hours, or a 4-hour inhalation exposure. Chemicals are sorted into categories by route (oral, dermal, inhalation) using LD50/LC50 cut-offs — Category 1 is the most toxic. OSHA's HazCom standard uses Categories 1–4.
Aspiration HazardA GHS health-hazard class for chemicals that can be fatal if swallowed and then enter the airways — directly or by vomiting — causing chemical pneumonia or lung injury. Thin, low-viscosity hydrocarbons (gasoline, kerosene, lamp oil) are the classic example. It is Category 1, with the health-hazard pictogram (GHS08) and signal word “Danger.”
CarcinogenicityA GHS health-hazard class for chemicals that cause cancer or increase its incidence. GHS (and OSHA's HazCom standard) sorts carcinogens into Category 1A (known human carcinogen), 1B (presumed, from animal evidence), and Category 2 (suspected). Carcinogens carry the health-hazard pictogram (GHS08) and a hazard statement such as H350 (“May cause cancer”).
Chemicals Under PressureA physical-hazard class added by OSHA's 2024 HCS update (aligning with GHS Revision 7) for liquids or solids pressurized with a gas, held in pressure receptacles other than aerosol dispensers and not classified as gases under pressure. It is categorized by the flammability of its contents and always carries the gas-cylinder pictogram (GHS04) for the pressure hazard.
ClassificationThe process of evaluating the available scientific evidence for a chemical against the GHS criteria to decide whether it is hazardous and, if so, the hazard class and category of each effect. Classification is the first step in HazCom — its result determines every label element (pictogram, signal word, hazard and precautionary statements) and SDS content.
Corrosive to MetalsA GHS physical-hazard class for chemicals that, by chemical action, will materially damage or even destroy metals. It is a single category (Category 1), determined by corrosion-rate testing on steel and aluminum, and uses the corrosion pictogram (GHS05) with the hazard statement H290. It is a separate hazard from skin corrosion, even though both use GHS05.
Desensitized ExplosivesA physical-hazard class added by OSHA's 2024 HCS update (GHS Revision 7) for solid or liquid explosives that have been phlegmatized — wetted or diluted — to suppress their explosive properties for safe transport and storage. It has four categories based on the corrected burning rate, and uses the flame pictogram (GHS02), not the exploding-bomb.
Globally Harmonized System (GHS)An internationally agreed framework created by the United Nations (first adopted in 2003) that standardizes how chemical hazards are classified and communicated — using common hazard classes, pictograms, signal words (Danger / Warning), and coded hazard (H) and precautionary (P) statements on labels and safety data sheets. The US adopted GHS into law through OSHA's 2012 Hazard Communication Standard update.
Sources & verification
- 29 CFR 1910.1200 App B.8 (eCFR / OSHA.gov)
- 29 CFR 1910.1200 (eCFR / OSHA.gov)
- OSHA — 1910.1200 Appendix B.8 (Self-Reactive Chemicals)
- OSHA — Hazard Communication (Physical Hazards)
Reviewed by HazComFast against eCFR, OSHA.gov, NIOSH, and the Federal Register. Last reviewed 2026-10-05. This glossary is general information, not legal advice; OSHA State-Plan states (e.g. California, Michigan) may adopt stricter requirements.
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