The Duration of Burning

The duration of burning is determined with a stop-watch, and is of importance in the case of set pieces, in which several kinds of mixtures are present. The time can then be regulated by altering the depth of the mixture in the cases shorter cases for slower mixtures, and longer cases for quicker mixtures, can be used. 

The duration of the fire test for air accident qualification was set at 60 min. Statistical data on fires resulting from air accidents support the conclusion that the 60 min thermal test exceeds most severe fire environments that a package would be likely to encounter in an aircraft accident. Fire duration statistics are frequently biased by the duration of burning of ground structures and other features not related to the aircraft wreckage, as well as by the location of consignments involved in the accident. To account for this effect, information on fire duration was evaluated carefully to avoid bias by accounts of fires that did not involve the aircraft. The fire test has the same characteristics as those specified in para. 728. 

The scope of this test is to determine the ability of materials to self-extinguish (i.e., upon removal of an ignition source, the material ceases to burn.) The flame is applied to the sample twice for 10 sec. There are three possible ratings for this test based on the duration of burning after the ignition source has been removed and the dripping behavior of the material. The criteria for each rating are shown below ... 

After reviewing the results of the trial burn, U.S. EPA will modify the permit conditions again, as necessary, to ensure that the operating conditions of the incinerator are sufficient to ensure compliance with incinerator standards and protection of human health and the environment. Owners/ operators of incinerators must comply with the final permit conditions for the duration of the permit, or until the permit is modified. 

A flash fire occurs when a vapor cloud of flammable material burns. The cloud is typically ignited on the edge and burns toward the release point. The duration of a flash fire is very short (seconds), but it may continue as a jet fire if the release continues. The combustion of an unconfined vapor cloud will generate... 

Once a mass-burning rate of the fire is established, the duration of the fire (burn time) can be calculated as ... 

If it is assumed that the fuel spill burns at the maximum rate for the duration of the fire, the burn time, tb [Equation (5-8)] for the fuel spill fire will be ... 

An unprotected person exposed to H vapor will suffer simultaneously from skin burns, eye injury, and irritation of the respiratory tract.20 The acute effects of H depend on the concentration of the gas, the duration of exposure, the ambient temperature, the extent of protection, and the susceptibility of the person.23 Clothing will be contaminated and become a secondary source of poisoning even after a gas cloud has blown away. 

Duration of burning The incendiary materials must not only impart high temperatures but also maintain heat generation without replenishment of fuel. The heat must continue to radiate for an appreciable time and when the heated object is ready to bum, the fire must be present to ignite it. In fact two factors viz. intensity of heat and duration of burning are complementary to each other and must satisfy the purpose of incendiary materials. 

The duration of the flame produced by the explosion is another important factor. The flame of a high explosive is of extremely short duration and may not be sufficient to ignite firedamp. Conversely the flame produced by burning blackpowder lasts much longer and is therefore more dangerous. Clearly, the duration and temperature of the flame of explosion are the factors which determine the safety of an explosive used in mines. 

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