12
(Class A) Wood-smoldered smoke generate method
The combustible for this test is to be to ten Ponderosa pine sticks (non-resinous, free from knots or
pitches) placed in a spoke pattern on the hotplate so that sticks are 36 degrees (0.63 rad) apart. The
end of each stick is to be flush with the edge of the hotplate. Each stick is to be 3 by 1 by 3/4 inches
(76.2 by 25.4 by 19.1 mm) with the 3/4 by 3 inch (19.1 by 76.2 mm) face in contact with the hotplate.
All surfaces of each stick are to be relatively smooth and free from burrs or holes. The grain of the
wood is to be parallel to the stick length. Each stick is to be conditioned for not less than 48 hours at
52°C (125°F) in an air-circulating oven. The stick weight is to be 16 ±2 grams (0.56 ±0.07 oz)
following the oven conditioning.
Exception: The above stick dimensions and the number and placement of sticks are variable as long
as the correct smoke buildup rates are achieved.
The heat source is to be a 240 volt, 1550 watt hotplate
m
having a steel plate 8-1/2 inches (216 mm) in
diameter and 1/4 inch (6.4 mm) thick, the top most portion of which is to be 8 inches (200 mm)
above the floor. The temperature of the hotplate is to be monitored by an iron constant an No. 30
AWG (0.05 mm
2
) (Type J) thermocouple attached to the edge of the steel plate by placing its junction
in a hole 0.015 inch (0.38 mm) in diameter and 1/4 inch (6.4 mm) deep and peening over the opening
to secure it. The thermocouple is to be connected to a proportioning temperature controller that is
able to be precisely set for the specified hotplate temperature. The controller sensitivity is to be
adjusted so that all conditions for this test are met. Once set for a specific temperature, the hotplate is
to be maintained at that temperature, (as monitored by a temperature measuring meter). Prior to the
start of the test, the hotplate temperature is to be 23 ±2°C (73 ±4°F). The initial proportioning
controller temperature setting is to be 205°C (401°F). The hotplate and controller are then to be
energized and the test time started (T = 0). The proportioning controller setting is to be increased to
obtain the temperature sequence specified in Table 40.1 and Figure 40.1 (the hotplate temperature
normally lags the controller setting by 2 minutes during the incremental increases).
