Interpretation ID: aiam3910
Manager
Photometric Division
ETL Testing Laboratories
Inc.
P.O. Box 2040
Cortland
NY 13045- 2040;
Dear Mr. Bonvallet: This is in reply to your letter of February 4, 1985, asking for a interpretation of the humidity testing procedure for replaceable bulb headlamps.; Paragraph S6.8 of Motor Vehicle Safety Standard No. 108 states i pertinent part that after completion of the test cycle in which the headlamp shall have been in an environment of 100 degrees Fahrenheit with a relative humidity of 90 *+* 10 percent, it shall then be in an environment with a temperature of 73 degrees Fahrenheit and relative humidity of 30 *+* 10 percent before removal for photometric testing. You believe that this implies an instantaneous transition in temperature/humidity conditions which, in your view, is 'impossible to achieve.' You have set forth three alternative procedures and ask which is the most acceptable to this agency.; Under your first alternative, the temperature and humidity in th humidity chamber would be reduced to 73 degrees Fahrenheit-43 percent, requiring about an hour, whereupon the headlamp would be removed to a 'dry box' chamber of the requisite temperature/humidity before photometric testing. In the second alternative, there would be no such removal before the photometric testing. In the third alternative, the headlamp would be removed from the humidity chamber and immediately carried to a 'dry box' with the requisite temperature/humidity, however, in your test set up this would require three to five minutes elapsed time between chambers.; Paragraph S6.8 does not specify a humidity of 43 percent in any of it test conditions, and a procedure incorporating the first and second alternatives clearly would not be in accordance with paragraph S6.8. That paragraph, however, does not specify that the temperature/humidity sequences must occur in the same chamber but it does imply that the lower temperature/humidity soak should take place directly following the higher temperature/humidity one. Therefore, your third alternative is the one that meets the intent of paragraph S6.8. To insure consistency of results, we recommend that no transfer period exceed three minutes and that the headlamp be exposed as briefly and as little as possible to the ambient temperature/humidity of the test laboratory.; Sincerely, Jeffrey R. Miller, Chief Counsel