Narrative:

During climb; the captain noted a smell similar to a 'rub strip' odor; normal during a 737 first flight. Because this was a first flight and no secondary indications were noted; we continued climb. Neither I nor other flight personnel initially smelled the odor. Later in the climb; other crewmembers also began to faintly smell the same odor. After cruise; the faint odor was again noted and seemed to intermittently dissipate. After completing high altitude checks and entering the lower altitude block of 14;000-16;000 ft; the flight analyst came forward to announce that he could smell fumes in the flight deck but not in the aft passenger cabin. The captain and I elected to don oxygen masks for the remainder of the flight. At that point; the crew elected to terminate further flight checks and return to the airport. We also ran appropriate checklists. While being vectored for final approach; we declared an emergency with approach control for priority handling and an uneventful approach and landing ensued. The fumes and actions taken were fully described during debrief with quality assurance and maintenance.

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Original NASA ASRS Text

Title: A B-737 flight test crew declared an emergency; donned oxygen masks; and returned to their departure airport due to recurring fumes in the cockpit.

Narrative: During climb; the Captain noted a smell similar to a 'rub strip' odor; normal during a 737 first flight. Because this was a first flight and no secondary indications were noted; we continued climb. Neither I nor other flight personnel initially smelled the odor. Later in the climb; other crewmembers also began to faintly smell the same odor. After cruise; the faint odor was again noted and seemed to intermittently dissipate. After completing high altitude checks and entering the lower altitude block of 14;000-16;000 FT; the Flight Analyst came forward to announce that he could smell fumes in the flight deck but not in the aft passenger cabin. The Captain and I elected to don oxygen masks for the remainder of the flight. At that point; the crew elected to terminate further flight checks and return to the airport. We also ran appropriate checklists. While being vectored for final approach; we declared an emergency with Approach Control for priority handling and an uneventful approach and landing ensued. The fumes and actions taken were fully described during debrief with Quality Assurance and Maintenance.

Data retrieved from NASA's ASRS site as of July 2013 and automatically converted to unabbreviated mixed upper/lowercase text. This report is for informational purposes with no guarantee of accuracy. See NASA's ASRS site for official report.