Narrative:

During cruise at FL250 the first officer (first officer) and I were having a conversation and mid-sentence we simultaneously noticed a strange odor. There was no visible smoke in the cockpit and we both agreed that it was not an electrical smell but something we could not identify. At that moment the flight attendant (flight attendant) used the cabin emergency button to notify us that there was smoke coming out of the passenger vents. I immediately turned off the recirculating fan and radioed ATC and needed to land as soon as possible. He asked what airport and I asked what was closest. He mentioned ZZZ was only 20 miles away and knowing the runway is long and the weather in the area is good chose that and asked to immediately start a descent and vectors for the airport. At that point I had the first officer take the radios and start getting down. We were given a lower altitude and he started a 3000 fpm descent. I then turned my attention to the QRH and ran the appropriate checklist. After turning off the gasper fan as well I wanted to know if that got rid of the smoke. I called the flight attendant back and she said that the smoke was no longer coming out just some residual smoke in the cabin. She also said that they were all ok and there was no need for passenger oxygen and then continued with the QRH. It seemed that the smoke was no longer as big a threat; so having coming to an end point in the QRH I then began to prepare for landing. Even though there didn't seem to be any new smoke; the possibility that there was still a fire we could not see was a huge concern. I used the speed cards to get landing numbers and since the QRH was out quickly looked at the landing distance. We were now approximately 3000 feet and I ran the descent checklist. Looking at our current weight I realized that were about 450 lbs. Overweight but decided it didn't matter. We were now getting vectored for approach and I just focused on landing. After landing we stopped on the runway and I told the passengers to remain seated. I communicated with ATC that I would like the fire trucks to check the aircraft for any issues we may not be aware of. At this point I made an announcement to the passengers to not be alarmed by the trucks; that we were just being overly cautious; that at this time there was no danger and to remain seated. After I called the flight attendant and asked if she and everyone else was ok. She said yes. After the fire trucks notified us that they could not see any damage or issues; we taxied to the gate; and deplaned normally.the smell was obvious to us and the cabin crew saw the smoke. It seemed to be an issue with either the recirculating fan; gasper fan or pack 2. I had meled pack 1 before we left the gate 3 flights prior. I believe we did everything we needed to and we landed with no injuries or damage to the aircraft. This has been an issue that to my knowledge has happened several times in the past few weeks and needs to be resolved. Not sure if it is the same aircraft or multiple ones.

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Original NASA ASRS Text

Title: EMR-145LR flight crew reported a strong unidentifiable odor at cruise; which resulted in a diversion.

Narrative: During cruise at FL250 the FO (First Officer) and I were having a conversation and mid-sentence we simultaneously noticed a strange odor. There was no visible smoke in the cockpit and we both agreed that it was not an electrical smell but something we could not identify. At that moment the FA (Flight Attendant) used the cabin emergency button to notify us that there was smoke coming out of the passenger vents. I immediately turned off the recirculating fan and radioed ATC and needed to land as soon as possible. He asked what airport and I asked what was closest. He mentioned ZZZ was only 20 miles away and knowing the runway is long and the weather in the area is good chose that and asked to immediately start a descent and vectors for the airport. At that point I had the FO take the radios and start getting down. We were given a lower altitude and he started a 3000 fpm descent. I then turned my attention to the QRH and ran the appropriate checklist. After turning off the gasper fan as well I wanted to know if that got rid of the smoke. I called the FA back and she said that the smoke was no longer coming out just some residual smoke in the cabin. She also said that they were all OK and there was no need for passenger oxygen and then continued with the QRH. It seemed that the smoke was no longer as big a threat; so having coming to an END point in the QRH I then began to prepare for landing. Even though there didn't seem to be any new smoke; the possibility that there was still a fire we could not see was a huge concern. I used the speed cards to get landing numbers and since the QRH was out quickly looked at the landing distance. We were now approximately 3000 feet and I ran the descent checklist. Looking at our current weight I realized that were about 450 lbs. overweight but decided it didn't matter. We were now getting vectored for approach and I just focused on landing. After landing we stopped on the runway and I told the passengers to remain seated. I communicated with ATC that I would like the fire trucks to check the aircraft for any issues we may not be aware of. At this point I made an announcement to the passengers to not be alarmed by the trucks; that we were just being overly cautious; that at this time there was no danger and to remain seated. After I called the FA and asked if she and everyone else was OK. She said yes. After the fire trucks notified us that they could not see any damage or issues; we taxied to the gate; and deplaned normally.The smell was obvious to us and the cabin crew saw the smoke. It seemed to be an issue with either the recirculating fan; gasper fan or pack 2. I had MELed pack 1 before we left the gate 3 flights prior. I believe we did everything we needed to and we landed with no injuries or damage to the aircraft. This has been an issue that to my knowledge has happened several times in the past few weeks and needs to be resolved. Not sure if it is the same aircraft or multiple ones.

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.