12-7A-4.7 Part A. Under-Deck Flame Test
- Burner. A 12 × 12 inch (300 × 300 mm) sand diffusion burner shall be used. Natural gas, methane or propane shall be supplied to the burner through a metered control system. The gas supply to the burner shall produce a net heat output of 80 ± 4 kW throughout the flame exposure. Burner output can be determined from HRR or calculated from the gas flow rate, temperature, and pressure.
- Oxygen depletion calorimeter. The equipment shall include a hood, associated ducting, and instrumentation to provide HRR data by oxygen depletion calorimetry.
See Figure No. 1.
- Deck support assembly. The assembly that holds the test deck over the burner.
- Baffle panels and joist support. Horizontal metal plates to support the deck joists along their full length, and also to confine burner flames to the underside of the deck boards located between the support joists.
- Back wall. Ceramic fiber board or another noncombustible panel product for the back wall material. Total height of the back wall shall be 8 feet (2.4 m).
- Ledger board. A 4-foot-long (1.2 m) simulated 2 x 6 ledger board shall be constructed of layers of ceramic fiber board (or other noncombustible panel product) and attached to the wall at a height slightly below the overhang of the rear deck board of the test deck.
- Airflow. The test shall be conducted under conditions of ambient airflow.
- Number of tests. Conduct the test on three replicate assemblies.
- Burner output verification. Without a deck in the apparatus, set the output of the burner to 80 ± 4 kW. Conduct a verification run of 3 minutes to ensure the heat release rate, and then turn off the burner.
- Measurement of heat release rate. HRR is measured during the tests with a properly calibrated oxygen depletion calorimeter. Since HRR is typically a post-test analysis, this criterion for Acceptance may be determined at the end of the test.
- Burner positioning. Center the burner directly under the middle deck board, midway between the joists. The distance from the top of the burner to the bottom of the deck boards shall be 27 inches (690 mm).
- Moisture content. Measure the moisture content of the wooden members of the assembly using a moisture meter (ASTM D 4444).
- 7.1. Ignition. Ignite the burner, controlling for a constant 80 ± 4 kW output.
- 7.2. Flame exposure. Continue the exposure for a 3-minute period. Extinguish the burner.
- 7.3. Continued combustion. Continue observation for an additional 40 minutes or until all combustion has ceased.
- Observations. Note physical changes of the deck boards during the test, including structural failure of any deck board, location of flaming and glowing ignition, and loss of material (i.e., flaming drops of particles falling from the deck). It is desirable to capture the entire test with a video recorder to allow review of the details of performance.
The report shall include a description of the deck board material and the time of any degradation (effective net peak heat release rate, structural failure, flaming drops or particles falling from the deck) during the test.
- 1.1. During the first 5 minutes of the test (the 3 minutes during which the ignition source burner is operating and the immediately following 2 minutes) the effective net peak HRR of the test assembly shall be reported as: effective net peak HRR = (peak heat release rate — 80 kW) / (deck surface area).
- 1.2. During the remaining test duration the effective net peak heat release rate of the test assembly shall be reported as: effective net peak HRR = (peak heat release rate) / (deck surface area).
Should one of the three replicates fail to meet the Conditions of Acceptance, three additional tests may be run. All of the additional tests must meet the Conditions of Acceptance.
- Effective net peak heat release rate of less than or equal to 25 kW/ft2(269 kW/m2).
- Absence of sustained flaming or glowing combustion of any kind at the conclusion of the 40-minute observation period.
- Absence of falling particles that are still burining when reaching the burner or floor.