Date: 202102
Local time of day: 1201-1800
Location: PSM.Airport, NH
Aircraft: Commercial Fixed Wing
Operator: Air Carrier
Operating under: Part 121
Flight plan: IFR
Flight phase: Landing
ATC / advisory: Tower PSM
Reporter organization: Air Carrier
Reporter function: Captain; Pilot Flying
Reporter qualification: Flight Crew Multiengine; Flight Crew Air Transport Pilot (ATP); Flight Crew Instrument
Human factors: Troubleshooting; Workload; Confusion; Distraction
Anomaly: Flight Deck / Cabin / Aircraft Event Smoke / Fire / Fumes / Odor; Ground Event / Encounter FOD
Detector: Person Flight Crew
When detected: In-flight
Result: Flight Crew Requested ATC Assistance / Clarification
Contributing factors: Human Factors; Procedure
Primary problem: Procedure

Narrative: After an uneventful approach and touchdown with Captain as Pilot Flying; the aircraft was decelerating normally with speed brakes and reversers deployed. The crew accomplished a normal exit of the runway when smoke could be seen in the flight deck and sirens sounded in the cabin. Purser was immediately contacted and told flight crew that there was smoke in the cabin and detectors going off. The Purser was asked to assess the situation in the cabin as simultaneous contact was made with the Tower. Cabin was asked for any signs of a fire or source of smoke and none were present. The Tower advised crew that a runway treatment had been used two days prior and that upon crew request no signs of smoke or fire were visible coming from aircraft. Crew determined it was safe to exit the runway taxiway due to smoke being from possible ingestion into the packs or reversers from chemicals in the runway area and proceed to the ramp with constant contact with the cabin to ensure no escalation or fire warnings.A short time later an evacuation message and siren was triggered in the flight deck. Once again we verified with cabin crew that no fire or source of smoke could be assessed. We requested that the emergency equipment be available and accompany the aircraft to the gate out of an abundance of caution and increasing warnings in the flight deck. A normal shut down was accomplished and the flight mechanic entered the flight deck and informed crew that he had inadvertently set off the evacuate warning while trying to cancel the smoke detectors in the cabin.Crew was met by local airport authorities and emergency personnel. During the interaction with crew we were informed that two compounds 'Sodium Formate' a liquid treatment and 'Potassium Acetate' mixed in with 'aviation grade sand' had been used two days prior and could possibly have been ingested by reverser system and packs leading to smoke. A giant smoke cloud could also be seen at the midpoint of the runway at least 200 feet tall but centered in one location; the possible site where chemicals interacted with the aircraft. Crew taking over the flight was briefed on the situation and Maintenance was in the process of examining the aircraft. By all logic with no indications of a fire and smoke being generated inside the aircraft an external source was deemed the most likely cause. The pebble sized compound that may have been present along runway edge and some portions of runway; even though runway appeared perfectly clean and clear were brought by airports OPS Crew after an inspection of touchdown and mid runway areas.With the compounds mentioned not being familiar to crews not much comment can be given; I would suggest familiarizing crews with this event to help discern an actual fire with a foreign contaminant causing indications of smoke and fire. I would also point out that procedures need to be followed in regards to on board mechanics response to dealing with abnormalities; rather than helping in trying to cancel an alarm after it was deemed non-threatening the issue was compounded which could have forced an evacuation had flight deck and cabin crew had poorer communication.




Synopsis: Air Carrier Captain reported smoke in the flight deck and cabin due to the reversers or packs ingesting chemicals that had been used to treat the runway surface.