Date: 202009
Local time of day: 1801-2400
Location: ZZZ.Airport, US
Flight conditions: VMC
Light: Night
Aircraft: Regional Jet 700 ER/LR (CRJ700)
Operator: Air Carrier
Operating under: Part 121
Flight plan: IFR
Mission: Passenger
Flight phase: Parked
Reporter organization: Air Carrier
Reporter function: Captain; Check Pilot; Pilot Not Flying
Reporter qualification: Flight Crew Instrument; Flight Crew Multiengine; Flight Crew Air Transport Pilot (ATP)
Human factors: Troubleshooting; Distraction
Second reporter function: Pilot Flying; First Officer
Anomaly: Deviation / Discrepancy - Procedural Published Material / Policy; Flight Deck / Cabin / Aircraft Event Smoke / Fire / Fumes / Odor
Detector: Person Flight Attendant; Person Flight Crew; Person Passenger
When detected: Aircraft In Service At Gate
Result: Aircraft Equipment Problem Dissipated; Flight Crew Overcame Equipment Problem; General Flight Cancelled / Delayed; General Maintenance Action
Contributing factors: Human Factors
Primary problem: Human Factors

Narrative: The FA (Flight Attendant) came up about 30 minutes prior to departure and said there was a smell; similar to when a gas stove is turned on but not lit; around the exit row. I was eating and asked the FO (First Officer) to go check it out. He came back and said the report was accurate; so I called Maintenance. I was busy eating and asked MX (Maintenance) if he wanted me to write it up; and he said no. He came on and said he had smelled something outside approaching the plane. Once I was done eating; I went back and smelled for myself. It was just as described. The confusing thing was that I had never smelled anything like it before; nor could myself; any passengers; Maintenance or the flight attendants determine what it could be. We continued trying to solve the problem; going up and down the cabin seeing if it was stronger one place versus the other; and seeing if it was dissipating. We did have a family of four leave the flight; English was not their first language so I am unsure if they understood my briefings. As we were dealing with that; we called OPS to notify them of the delay. Shortly after; our mechanic came up and said they noticed a ramp sweeping machine that runs on propane nearby. Then Operations called and said it was a tug nearby that was leaking fuel. With this information; we decided we would pushback and see if it goes away after we left the gate area. We did and checked with the flight attendant twice during taxi to get an update. The first time she said it was dissipating; and on the before takeoff check to the line; she said it was gone. During descent; in the mid-teens; we got a call saying the smell was back. It wasn't busy so we asked for a quicker route to the airport; which was granted and we landed uneventfully. I have no good answer as to why I didn't write this up. I have thought about it since I got off the phone with Maintenance in ZZZ1; and I cannot think of a reason why I decided to not write this up. Referring to [the] manual. Mechanical Irregularities; D. Reporting Mechanical Irregularities; it does not specifically state to write anything in the MX Log. It simply states if the item is notice prior to block out; to contact Maintenance and they will determine the action required to correct or defer the irregularity. I will re-write to read that any time Maintenance is contacted; a write muse ensue.


Second narrative: As we were doing preflight duties a FA (Flight Attendant) reported an odd smell in the cabin while passengers were boarding around the exit row. The Captain (CA) asked me to go back and see what I smelled and I did. It was like a natural gas smell mixed with garbage. Nothing I could place a finger on. I reported it to the CA and he went back to check it out. I continued preflight work and he called Mx (Maintenance) out. I didn't hear his and Mx conversation as I continued preflight activities But at the end he told me that the Mx guy could smell it outside and that there was a fuel spill reported from a ground truck in the gate next to us that was the most likely cause of the smell. I continued preflight activities as the Captain finished working with Mx. and he said we were good to depart as long as the smell disappeared when we taxied out. We called the FA on taxi and she said it had dissipated and we departed. On arrival the smell returned and after we reached the gate and shutdown the Captain determined that he had not written up the issue properly in the origin airport before we departed. I believe the Captain was distracted with many tasks and worrying about departing on time which caused him to forget to write up the issue. It's difficult to find a single reason on how to avoid this event. Perhaps more training on specific events that require Mx write ups.


Synopsis: CRJ-700 flight crew reported a fumes event during pre-flight; which was described as a natural gas" smell. Maintenance told the crew there was a fuel spill outside the aircraft which was most likely the cause of the smell.  The crew decided to depart and the smell dissipated on taxi-out."