Narrative:

At cruise flight at FL260 there was a faint smoke smell. After querying with the PIC if it was just me; we confirmed that we both smelt it. Four passengers in the back also confirmed the smell and that it was from the back of the cabin. There were no indication of anything abnormal on any system; no warning or caution lights and no abnormalities in the pressurization or environmental systems. We ran memory items for electrical smoke and as the smell was from the back turned off the interior master switch. At this point we communicated with ATC our intent to divert due to a smoke smell and coordinated a diversion to [a nearby alternate]. The PIC was flying and I was pilot monitoring. I proceeded to pull and run the checklist for electrical smoke. There was never more than a fumes smell (prior to donning oxygen) and a slight haze in the aft cabin. In the descent we manually deployed the passenger oxygen. After getting configured and set up for the approach we landed uneventfully; stopped briefly on the runway and talked with [ground personnel] as they did a brief inspection prior to us taxiing to the ramp. With nothing more than a faint smell at this time we decided it would be safe to taxi to the ramp and shut down and deplane there. We talked with the [ground] personnel who checked over the plane and found nothing more than a faint smell at that time.

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Original NASA ASRS Text

Title: BE300 First Officer reported diverting to an alternate airport after noticing smoke odor in the aircraft.

Narrative: At cruise flight at FL260 there was a faint smoke smell. After querying with the PIC if it was just me; we confirmed that we both smelt it. Four passengers in the back also confirmed the smell and that it was from the back of the cabin. There were no indication of anything abnormal on any system; no warning or caution lights and no abnormalities in the pressurization or environmental systems. We ran memory items for electrical smoke and as the smell was from the back turned off the interior master switch. At this point we communicated with ATC our intent to divert due to a smoke smell and coordinated a diversion to [a nearby alternate]. The PIC was flying and I was Pilot Monitoring. I proceeded to pull and run the checklist for electrical smoke. There was never more than a fumes smell (prior to donning oxygen) and a slight haze in the aft cabin. In the descent we manually deployed the passenger oxygen. After getting configured and set up for the approach we landed uneventfully; stopped briefly on the runway and talked with [ground personnel] as they did a brief inspection prior to us taxiing to the ramp. With nothing more than a faint smell at this time we decided it would be safe to taxi to the ramp and shut down and deplane there. We talked with the [ground] personnel who checked over the plane and found nothing more than a faint smell at that time.

Data retrieved from NASA's ASRS site 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.