Interpretation ID: nht92-2.21

DATE: November 18, 1992

FROM: L. J. Sharman

TO: NHTSA, Department of Transportation

TITLE: None

ATTACHMT: Attached to letter dated 3-23-93 from John Womack to L. J. Sharman (A40; Std. 302)

TEXT: Recently, two questions have arisen concerning the procedure to be followed when conducting the flammability test method specified in Motor Vehicle Safety Standard No. 302. Each of the questions, the writers answer and rationale are given on the attached sheets. I am writing to request an advisory opinion as to whether these answers are correct, if not what the correct interpretation should be.

Thank you for your prompt attention to this matter.

QUESTIONS CONCERNING THE FLAMMABILITY TEST PROCEDURE SPECIFIED IN MVSS-302

QUESTION 1.

MVSS-302, in Section S5.3(e), states that the timing for each specimen be started when the flame from the burning specimen reaches a point 1.5 inches from the open end of the specimen and, in Section S5.3(f), is stopped when the flame progresses to a point 1.5 inches from the clamped end of the specimen. Further, the Standard, in Section S5.2.2, states the specimen is oriented so that the surface closest to the occupant compartment air space faces downward on the test frame. The question that has been raised is whether the timing is started and stopped when the flame reaches the designated points on the surface of the specimen closest to the occupant compartment air spaces (the surface facing down during the test), or when the flame reaches the designated points on the surface of the specimen facing away from the occupant compartment air space (the surface facing up during the test).

ANSWER

Timing of the flame should start when the flame from the burning specimen reaches the 1.5 inch point on the surface facing up during the test and stopped when the flame progresses to a point 1.5 inches from the clamped end of the specimen on the surface facing up during the test.

RATIONALE

The Standard states that the bunsen burner and the specimen are positioned so that the center of the bottom edge of the open end of the specimen. While the Standard does not specify how far above the cabinet floor the specimen must be located, the bunsen burner and flame height specified above effectively define this distance. At that height, it is extremely difficult if not impossible to observe the flame front underneath the specimen. If the intent of the standard was to observe the flame front test cabinet floor or some other means of

observing the flame front. Since NHTSA did not make such requirements, the logical location points for starting and stopping the timing are on the surface facing up during the test.

QUESTION 2.

MVSS-302, in Section S5.3(f), states that the flame progression be measured to a point 1.5 inches rom the clamped end of the specimen under test. The standard does not specify actions to be taken after timing has stopped. Some laboratories put out the flame using a small amount of water from a spray bottle. The question has been raised as to whether using a small amount of water from a spray bottle to put out the flame is an acceptable procedure.

ANSWER

The use of a small amount of water from a spray bottle is believed to be acceptable.

RATIONALE

The primary concern with the use of water to put out the flame is whether the water would affect the humidity in the test chamber and, therefore, the test results. MVSS 302 states in Section S5.1.2 that prior to testing each specimen be conditioned at a temperature of 70 degrees F. and a relative humidity of 50 percent, and the test be conducted under those ambient conditions. The Standard does not specify the humidity limits within which the test must be conducted. Considering the short time the specimen is in the chamber before burning and the small amount of water used it is believed that the humidity would not be significantly affected and therefore the procedure to be both acceptable and a good safety precaution.