Deflagration ability in an open system: UN Series C, Test C.2
This test is used to determine whether a test substance is able to propagate a deflagration in an open system. The test substance as well as the Dewar vessel (see figure) are heated to a test temperature of approx. 50 °C. The Dewar vessel is then used for the test. The test substance is then filled into the Dewar vessel approx. 20 mm below the rim. The mass and temperature of the test substance are recorded. The Dewar vessel is then placed behind a shield in a fume chamber. The test substance is heated at the top with a gas burner (propane burner) for at least five minutes.
If ignition occurs, the gas burner is removed. The time taken for the reaction zone to pass the distance between the marks of 50 and 100 mm from the top of the Dewar vessel is measured. If no ignition occurs within five minutes or if the reaction zone stops before reaching the lower mark, the test substance is considered as not deflagrating.
If an ignition occurs and the reaction zone reaches the lower mark, the shortest time interval is used to calculate the deflagration rate.
| Result | Classification according to UN Test C.2 |
| The deflagration rate is greater than 5.0 mm/s. | “Yes, rapidly” |
| The deflagration rate is less than or equal to 5.0 mm/s and greater than or equal to 0.35 mm/s. | “Yes, slowly” |
| The deflagration rate is less than 0.35 mm/s or the reaction stops before reaching the lower mark. | “No” |
(A) Height of filling 20 mm below rim
(B) 30 mm region for deflagration to be established
(C) 50 mm region for measuring the deflagration rate