A crj-700 developed a strong odor accompanied by the smoke aft lav master caution warning after take...

Narrative:

On initial climbout; we noticed a strong odor which was followed by the illumination of the 'smoke aft lav' master warning (red) light. We declared an emergency and requested an immediate return to the field. I ran the checklist while the first officer took over ATC. Flight attendants confirmed there was a very strong odor but no significant or detectable smoke. After completing the checklist; we made a normal approach and landing at ZZZ. Crash fire rescue equipment checked and confirmed there was no indication of fire or damage to the aircraft; so we taxied to the gate for a normal deplaning. We did not detect any smoke in the flight deck. The initial master warning message extinguished after we completed the checklist; which included pulling several cbs. After arrival at the gate; maintenance personnel informed us that the aircraft had an engine wash overnight; and they suspected the fumes were caused by residual chemical substances in the engines. This has not been confirmed by me as the actual cause of this event.

Original NASA ASRS Text

Title: A CRJ-700 developed a strong odor accompanied by the SMOKE AFT LAV Master Caution Warning after takeoff. An emergency return to land was completed. The crew was told that an engine wash the previous night that may have left a chemical residue in the engines.

Narrative: On initial climbout; we noticed a strong odor which was followed by the illumination of the 'SMOKE AFT LAV' Master Warning (Red) light. We declared an emergency and requested an immediate return to the field. I ran the checklist while the First Officer took over ATC. Flight Attendants confirmed there was a very strong odor but no significant or detectable smoke. After completing the checklist; we made a normal approach and landing at ZZZ. CFR checked and confirmed there was no indication of fire or damage to the aircraft; so we taxied to the gate for a normal deplaning. We did not detect any smoke in the flight deck. The initial Master Warning message extinguished after we completed the checklist; which included pulling several CBs. After arrival at the gate; maintenance personnel informed us that the aircraft had an engine wash overnight; and they suspected the fumes were caused by residual chemical substances in the engines. This has not been confirmed by me as the actual cause of this event.

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.

Attributes
ACN	828138
Time
Date	200903
Local Time Of Day	0601-1200
Place
Locale Reference	ZZZ.Airport
State Reference	US
Aircraft 1
Make Model Name	Regional Jet 700 ER/LR (CRJ700)
Operating Under FAR Part	Part 121
Flight Phase	Takeoff
Flight Plan	IFR
Person 1
Function	Pilot Flying Captain
Qualification	Flight Crew Air Transport Pilot (ATP)
Person 2
Function	Flight Attendant (On Duty)
Events
Anomaly	Deviation - Procedural Maintenance Flight Deck / Cabin / Aircraft Event Smoke / Fire / Fumes / Odor

A crj-700 developed a strong odor accompanied by the smoke aft lav master caution warning after takeoff. An emergency return to land was completed. The crew was told that an engine wash the previous night that may have left a chemical residue in the engines.