Narrative:

Flying at FL360 direct; the flight attendants called us and reported an acrid smell in mid-cabin. We smelled it shortly after and donned the oxygen masks. First officer was the pilot flying so he kept aircraft control and worked the radios. The captain worked the checklists and communicated with the flight attendants. We requested a descent from ATC while telling them of smoke in the cabin. An emergency was declared. They told us the nearest airfield so we got vectors to that field. While descending and getting vectors; the checklist was run. At the appropriate points; the flight attendants were asked if any of the smell was dissipating. They said that it seemed to be weaker. We asked if they saw smoke. They acknowledged haziness to the air. Since the smell was dissipating; when we landed; we asked the fire department to look from the outside and notify us if they saw any obvious problems. They didn't so we taxied to the gate and deplaned the passengers. We landed ten minutes after the first indication. Maintenance was notified. Contract maintenance came and did the inspections. We found that the gasper fan had gone bad and had caused the smoke and odors. Upon review of the checklists; I realized that the gasper fan isn't named as a specific person's duty so I should be checking it on every flight. I have often left that to the flight attendant. Had this happened below 10;000 ft; though; it would have been even more difficult and more threats would have been added to the event. We need to either add gasper fans to the 10;000 ft checklist or disconnect them. I will remember to check the gasper fan switch at 10;000 ft.

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Original NASA ASRS Text

Title: A B737-300 Gasper Fan failed in flight and caused acrid cabin fumes; but not knowing the odors source the pilots donned oxygen; declared an emergency and diverted to a nearby airport where Maintenance discovered the cause.

Narrative: Flying at FL360 direct; the flight attendants called us and reported an acrid smell in mid-cabin. We smelled it shortly after and donned the oxygen masks. First Officer was the pilot flying so he kept aircraft control and worked the radios. The Captain worked the checklists and communicated with the flight attendants. We requested a descent from ATC while telling them of smoke in the cabin. An emergency was declared. They told us the nearest airfield so we got vectors to that field. While descending and getting vectors; the checklist was run. At the appropriate points; the flight attendants were asked if any of the smell was dissipating. They said that it seemed to be weaker. We asked if they saw smoke. They acknowledged haziness to the air. Since the smell was dissipating; when we landed; we asked the Fire Department to look from the outside and notify us if they saw any obvious problems. They didn't so we taxied to the gate and deplaned the passengers. We landed ten minutes after the first indication. Maintenance was notified. Contract Maintenance came and did the inspections. We found that the gasper fan had gone bad and had caused the smoke and odors. Upon review of the checklists; I realized that the gasper fan isn't named as a specific person's duty so I should be checking it on every flight. I have often left that to the flight attendant. Had this happened below 10;000 FT; though; it would have been even more difficult and more threats would have been added to the event. We need to either add gasper fans to the 10;000 FT Checklist or disconnect them. I will remember to check the gasper fan switch at 10;000 FT.

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.