Narrative:

Passing through approximately FL260 notified by B flight attendant that aft lav smoke detector had activated. As pilot monitoring; I initially handled this call. Captain then gave me the aircraft and radios and said he would talk with the flight attendant. During the course of his conversation; the smoke alarm went out. The captain then consulted with me and we agreed we needed to run the cabin/lavatory fire checklist in the QRH. The captain also was able to quickly speak with dispatch; who concurred with running the same checklist. ZZZ was the closest suitable divert airfield (approximately 46-50 miles south) and we notified ATC of our need to divert. We explained the nature of our problem and eventually declared an emergency. We accomplished the QRH and diversion checklist; got ZZZ ATIS; and programmed the performance computer. Planned a flaps 40 overweight landing and knew we needed to run the brake cooling module after landing.after landing; we stopped straight ahead on the runway and had the fire department look over the aircraft. Initially had trouble contacting them on their radio frequency; but soon made contact. After their survey; fire department said the aircraft appeared safe to taxi clear and head to the gate. During the course of their inspection; I ran the brake cooling module; which showed we had a long brake cooling period (60+ minutes?) and potential for fuse plugs releasing. As soon as the fire department cleared us; I began to coordinate with ops for a gate that was ok for a hot brake aircraft. At this point a flight attendant called from the back and the captain handled the call. I heard something about smoke/wire burning smell and then evacuation. I stopped talking with operations and began to run the passenger evacuation checklist from the QRH as directed by the captain. Egress down the slides was uneventful and we gathered crew/passengers together to await transportation to terminal.

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Original NASA ASRS Text

Title: B737 flight crew was informed by the cabin crew of a lavatory smoke alarm activation for no apparent reason at FL260. The crew elected to divert and declared an emergency. After landing a Flight Attendant reported smelling electrical fumes and during the discussion with the Captain an evacuation occured without being ordered.

Narrative: Passing through approximately FL260 notified by B Flight Attendant that Aft Lav Smoke Detector had activated. As pilot monitoring; I initially handled this call. Captain then gave me the aircraft and radios and said he would talk with the Flight Attendant. During the course of his conversation; the smoke alarm went out. The Captain then consulted with me and we agreed we needed to run the Cabin/Lavatory Fire checklist in the QRH. The Captain also was able to quickly speak with Dispatch; who concurred with running the same checklist. ZZZ was the closest suitable divert airfield (approximately 46-50 miles south) and we notified ATC of our need to divert. We explained the nature of our problem and eventually declared an emergency. We accomplished the QRH and Diversion Checklist; got ZZZ ATIS; and programmed the performance computer. Planned a Flaps 40 overweight landing and knew we needed to run the Brake Cooling Module after landing.After landing; we stopped straight ahead on the runway and had the Fire Department look over the aircraft. Initially had trouble contacting them on their radio frequency; but soon made contact. After their survey; Fire Department said the aircraft appeared safe to taxi clear and head to the gate. During the course of their inspection; I ran the Brake Cooling Module; which showed we had a long brake cooling period (60+ minutes?) and potential for fuse plugs releasing. As soon as the Fire Department cleared us; I began to coordinate with Ops for a gate that was OK for a hot brake aircraft. At this point a Flight Attendant called from the back and the Captain handled the call. I heard something about smoke/wire burning smell and then evacuation. I stopped talking with Operations and began to run the Passenger Evacuation checklist from the QRH as directed by the Captain. Egress down the slides was uneventful and we gathered crew/passengers together to await transportation to terminal.

Data retrieved from NASA's ASRS site as of April 2012 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.