Class 4 Flammable Solids (pg 1 of 2)
These pages provide US DOT (U.S. Department of Transportation) definitions for class 4 flammable solids. Title 49 of the United States Code of Federal Regulations (49CFR) also known as the Federal Motor Carriers Safty Regulations (FMCSR) requires the use hazardous materials placards when shipping hazardous materials cargo and dangerous goods in the United States. Canada, Mexico and many other countries have simular regulations that also require the use of these placards.
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Division 4.1 Flammable Solid
Flammable solid (Division 4.1) means any of the following three types of materials:
- Desensitized explosives that-
- When dry are Explosives of Class 1 other than those of compatibility group A, which are wetted with sufficient water, alcohol, or plasticizer to suppress explosive properties; and
- Are specifically authorized by name either in the 49CFR 172.101 Table or have been assigned a shipping name and hazard class by the Associate Administrator for Hazardous Materials Safety under the provisions of-
- An exemption issued under subchapter A of this chapter; or
- An approval issued under 49CFR 173.56(i) of this part.
- Self-reactive materials are materials that are thermally unstable and that can undergo a strongly exothermic decomposition even without participation of oxygen (air). A material is excluded from this definition if any of the following applies:
- The material meets the definition of an explosive as prescribed in subpart C of this part, in which case it must be classed as an explosive;
- The material is forbidden from being offered for transportation according to 49CFR 172.101 of this subchapter or 49CFR 173.21;
- The material meets the definition of an oxidizer or organic peroxide as prescribed in subpart D of this part, in which case it must be so classed;
- The material meets one of the following conditions:
- Its heat of decomposition is less than 300 J/g; or
- Its self-accelerating decomposition temperature (SADT) is greater than 75°C (167°F) for a 50 kg package; or
- The Associate Administrator for Hazardous Materials Safety has determined that the material does not present a hazard which is associated with a Division 4.1 material.
- Generic types. Division 4.1 self-reactive materials are assigned to a generic system consisting of seven types. A self-reactive substance identified by technical name in the Self-Reactive Materials Table in 49CFR 173.224 is assigned to a generic type in accordance with that Table. Self-reactive materials not identified in the Self-Reactive Materials Table in 49CFR 173.224 are assigned to generic types under the procedures of paragraph (a)(2)(iii) of this section.
- Type A. Self-reactive material type A is a self-reactive material which, as packaged for transportation, can detonate or deflagrate rapidly. Transportation of type A self-reactive material is forbidden.
- Type B. Self-reactive material type B is a self-reactive material which, as packaged for transportation, neither detonates nor deflagrates rapidly, but is liable to undergo a thermal explosion in a package.
- Type C. Self-reactive material type C is a self-reactive material which, as packaged for transportation, neither detonates nor deflagrates rapidly and cannot undergo a thermal explosion.
- Type D. Self-reactive material type D is a self-reactive material which-
- 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; or
- Does not detonate or deflagrate at all and shows a medium effect when heated under confinement.
- Type E. Self-reactive material type E is a self-reactive material which, in laboratory testing, neither detonates nor deflagrates at all and shows only a low or no effect when heated under confinement.
- Type F. Self-reactive material type F is a self-reactive material which, in laboratory testing, 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.
- Type G. Self-reactive material type G is a self-reactive material which, in laboratory testing, does not detonate in the cavitated state, will not deflagrate at all, shows no effect when heated under confinement, nor shows any explosive power. A type G self-reactive material is not subject to the requirements of this subchapter for self-reactive material of Division 4.1 provided that it is thermally stable (self-accelerating decomposition temperature is 50 °C (122 °F) or higher for a 50 kg (110 pounds) package). A self-reactive material meeting all characteristics of type G except thermal stability is classed as a type F self-reactive, temperature control material.
- Procedures for assigning a self-reactive material to a generic type. A self-reactive material must be assigned to a generic type based on-
- Its physical state (i.e. liquid or solid), in accordance with the definition of liquid and solid in 49CFR 171.8 of this subchapter;
- A determination as to its control temperature and emergency temperature, if any, under the provisions of 49CFR 173.21(f);
- Performance of the self-reactive material under the test procedures specified in the UN Recommendations on the Transport of Dangerous Goods, Tests and Criteria and the provisions of paragraph (a)(2)(iii) of this section; and
- Except for a self-reactive material which is identified by technical name in the Self-Reactive Materials Table in 49CFR 173.224(b) or a self-reactive material which may be shipped as a sample under the provisions of 49CFR 173.224, the self-reactive material is approved in writing by the Associate Administrator for Hazardous Materials Safety. The person requesting approval shall submit to the Associate Administrator for Hazardous Materials Safety the tentative shipping description and generic type and-
- All relevant data concerning physical state, temperature controls, and tests results; or
- An approval issued for the self-reactive material by the competent authority of a foreign government.
- Tests. The generic type for a self-reactive material must be determined using the testing protocol from Figure 14.2 (Flow Chart for Assigning Self-Reactive Substances to Division 4.1) from the UN Recommendations on the Transport of Dangerous Goods, Tests and Criteria.
- Readily combustible solids are materials that-
- Are solids which may cause a fire through friction, such as matches;
- Show a burning rate faster than 2.2 mm (0.087 inches) per second when tested in accordance with UN Manual of Tests and Criteria; or
- Any metal powders that can be ignited and react over the whole length of a sample in 10 minutes or less, when tested in accordance with UN Manual of Tests and Criteria.
Division 4.2 Spontaneously Combustible
Spontaneously combustible material (Division 4.2) means-
- A pyrophoric material. A pyrophoric material is a liquid or solid that, even in small quantities and without an external ignition source, can ignite within five (5) minutes after coming in contact with air when tested according to the UN Manual of Tests and Criteria.
- A self-heating material. A self-heating material is a material that, when in contact with air and without an energy supply, is liable to self-heat. A material of this type which exhibits spontaneous ignition or if the temperature of the sample exceeds 200 °C (392 °F) during the 24-hour test period when tested in accordance with paragraph 3.b.(1) of appendix E to this part, is classed as a Division 4.2 material.
Division 4.3 Dangerous When Wet
Dangerous when wet material (Division 4.3) means a material that, by contact with water, is liable to become spontaneously flammable or to give off flammable or toxic gas at a rate greater than 1 liter per kilogram of the material, per hour, when tested in accordance with UN [United Nations] Manual of Tests and Criteria.
Last updated: March 2000
- Guide for Handling Household Chemicals
Things you can do to make your home safer.
- USDOT Hazardous Materials Table 49 CFR 172.101
An online version of the USDOT hazardous materials table from 49CFR 172.101. This table can be sorted by proper shipping name, UN/NA ID and/or by primary hazard class/division.
- ERG (Emergency Response Guidebook)
Have you ever wondered what those four digit numbers on the placards on the side of trucks and rail cars mean? Our online 2004ERG will give you your answer. This is an online version of the guidebook produced by the USDOT for first responders during the initial phase of a Dangerous goods/HazMat incident.
- Chemical Database
This database focuses on the most common chemical compounds used in the home and industry.
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Kenneth Barbalace. USDOT HazMat Placards - Class 4 Flammable Solids. EnvironmentalChemistry.com. 1995 - 2023. Accessed on-line: 9/23/2023
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