The oxidizing solids test is a procedure used to determine the oxidizing properties of solid substances. These tests are essential for classifying and identifying hazardous materials, especially those that have the potential to promote or contribute to combustion. The primary objective of the test is to assess whether a solid substance, when in contact with combustible or reducing materials, can cause or significantly aid in the combustion of those materials. Substances identified as oxidizing solids are assigned specific hazard classifications, labels, and identification numbers according to international transportation regulations (such as the UN/DOT classification system) for safe handling and transportation.
TESTING PRINCIPLE AND METHODOLOGY
The Procedure determines potential of solid substances to increase the burning rate of other combustible substances when they are mixed together. The selected substance is mixed with fibrous cellulose and tested against a reference sample (potassium bromate mixed with cellulose).
The test sample is mixed in 4:1 and 1:1 mass ratio to cellulose while reference sample is mixed in 3:7 (and if needed 2:3, 3:2) mass ratio to cellulose. The Cellulose used is a fiber with length between 50 and 250 μm and mean diameter of 25 μm. It is dried in a layer of maximum 25 mm thick at 105 °C to constant mass (at least 4 hours) and is kept in desiccator (with desiccant) until cool and required to use.
The Reference sample is technically a pure potassium bromate that is sieved (not grounded) and fraction with nominal particle sizes in the range 0.15 to 0.30 mm. It is dried for at least 12 hours in 65 °C to achieve constant mass and kept in desiccator (with desiccant) until cool and required for use.
The sample is tested in the form in which it will be transported. The substance is inspected for any particles less than 500 μm in diameter. If that powder constitutes more than 10% (mass) of the total, or if the substance is friable, then the whole of the test sample is ground to a powder before testing to allow for a reduction in particle size during handling and transport.
The first test is performed with the reference sample in 3:7 ratio. 30 g ± 0,1 g of mixture is used to form a truncated conical pile using funnel. Pile base should be 70 mm in diameter. Pile should cover the looped of the ignition wire. Once sealed, the sample is placed inside the funnel. The funnel with the sample is then placed on the heating wire. At the same time, the heating element is turned on and the timer started. The time to completion of the main reaction (eg, flame, glow, or glow) is recorded. Intermittent reactions such as arcing or spraying after the main reaction are ignored. If the mixture does not ignite and does not burn within 3 minutes, the test is ended.
Applicable Standard
The test is performed according to UN Recommendation on the Transport of Dangerous Goods. Manual of Tests and Criteria; Test O.1: Test for oxidizing solids.
Data Interpretation
The mean burning time from five tests is compared to burning time of reference sample in 3:7 ratio. If test sample does not burn or ignite or burning time is greater than that of reference sample, test sample is classified as “Not Division 5.1”. Otherwise test reference sample in 2:3 ratio and 3:2 ratio if needed. Final classification is done using following criteria:
Packing group I: Any substance which, in the 4:1 or 1:1 sample to cellulose ratio (by mass) tested, exhibits a mean burning time less than the burning time of a 3:2 mixture, by mass, of potassium bromate and cellulose.
Packing group II: Any substance which, in the 4:1 or 1:1 sample to cellulose ratio (by mass) tested, exhibits a mean burning time equal to or less than the burning time of a 2:3 mixture (by mass) of potassium bromate and cellulose, and which does not meet the criteria for packing group I.
Packing group III: Any substance which, in the 4:1 or 1:1 sample to cellulose ratio (by mass) tested, exhibits a mean burning time equal to or less than the burning time of a 3:7 mixture (by mass) of potassium bromate and cellulose, and which does not meet the criteria for packing group I and II.
Not Division 5.1: Any substance which, in both the 4:1 and 1:1 sample to cellulose ratio (by mass) tested, does not ignite or burn, or exhibits mean burning times greater than that of a 3:7 mixture (by mass) of potassium bromate and cellulose.
When to perform Oxidizing Solids test
The oxidizing solids test is recommended in several scenarios, primarily to assess the oxidizing properties of solid substances and identify potential fire hazards associated with these materials. The test is recommended before transporting or handling solid substances, especially in industrial or commercial settings for appropriate hazard classification and labeling as per regulatory requirements, when developing or during SDS creation to include the appropriate hazard information and before shipping solid substances, particularly for long distances or storage in confined spaces to determine appropriate packaging, segregation, and transport conditions to prevent potential fire hazards.
Why work with Prime Process Safety Center
- Prime Process Safety Center is a leader in process safety testing with very experienced laboratory personnel. At Prime Process Safety Center our goal is to provide accurate, reliable and defensible data that meets industry and regulatory standards. We understand the need for the quality of your data, and we work assiduously to achieve just that.
- We are knowledgeable and experienced in performing oxidizing solids tests, ensuring accurate and reliable results.
- We have state-of-the-art oxidizing solids testing equipment, providing precise and sensitive measurements.
- We follow strict testing protocols and quality control measures to ensure consistent and reliable test results.
- Our team can interpret and analyze the data obtained from the tests, providing valuable insights and recommendations for your specific application or research.
FAQS
What Are Oxidizing Solids?
Answer: Oxidizing solids are substances that, in contact with combustible or reducing materials, can cause or significantly aid in the combustion of those materials by providing oxygen, even without atmospheric oxygen.
How Are Oxidizing Solids Identified?
Answer: Oxidizing solids are identified through laboratory tests that assess their ability to promote or intensify combustion. The testing determines if the substance exhibits oxidizing properties under specific conditions.
Why Are Oxidizing Solids Hazardous?
Answer: Oxidizing solids pose a fire hazard because they have the potential to initiate or accelerate the combustion of other materials, increasing the risk of fire or explosion in their presence.
What Are the Safety Precautions for Handling Oxidizing Solids?
Answer: Safety precautions include storing oxidizing solids separately from flammable materials, using appropriate containers to prevent contamination, avoiding heat sources, and following proper handling and disposal procedures.
What Regulations Govern the Handling and Transport of Oxidizing Solids?
Answer: The transportation and handling of oxidizing solids are regulated by various international standards and guidelines, such as those established by the UN, DOT, and other regulatory bodies, outlining specific packaging, labeling, and transportation requirements.