30 CFR § 7.28 Test for flame resistance of rigid ventilation tubing.
(a)Test procedures. (1) Prepare 6 samples of ventilation
tubing 48 inches in length with all flared or thickened ends removed. Any
sample with a cross-sectional dimension greater than 24 inches must be tested
in a 24-inch size.
(2) For each test, suspend the sample in the center of the
gallery by running a wire through the 48-inch length of tubing.
(3) Use a front exhaust system to remove smoke escaping
from the gallery. The exhaust system must remain on during all testing but
not affect the air flow in the gallery.
(4) Set the methane-fueled impinged jet burner to yield a
flame height of 12 inches as measured at the outermost tip of the flame.
(5) Apply the burner to the front lower edge of the tubing
so that two-thirds of the burner is under the tubing and the remaining third
is exposed to allow the flames to curl onto the inside of the tubing. Keep
the burner in contact with the material for 60 seconds. If melting material
might clog the burner orifices, rotate the burner slightly during application
of the flame.
(6) Test 3 samples in still air and 3 samples with an
average of 125 ft./min. of air flowing past the sample.
(7) Record the propagation length and duration of burning
for each of the 6 samples. The duration of burn is the total burning time of
the specimen during the flame test. This includes the burning time of any
material that falls on the floor of the test gallery during the igniting
period. However, the suspended specimen is considered burning only after the
burner is removed. Should the burning time of a suspended specimen and a
specimen on the floor coincide, count the coinciding burn time only once.
(8) Calculate the average duration of burning for the
first 3 samples (still air) and the second 3 samples (125 ft./min. air
(b)Acceptable performance. The ventilation tubing shall meet
each of the following criteria:
(1) Flame propagation of less than 4 feet in each of the 6
(2) An average duration of burning of less than 1 minute
in both groups of 3 tests.
(3) A duration of burning not exceeding 2 minutes in each
of the 6 tests.