On this day in 1985, British Airtours Flight 28M was beginning its takeoff run at Manchester Airport, bound for Corfu. An engine failed, and fire broke out. The aircraft was brought to a stop and the takeoff abandoned, but fire and smoke reached the cabin very quickly. Fifty-five people died, most of them from smoke inhalation. Eighty-two survived.
The cabin crew stayed at the doors, working in smoke to get people out. The investigation that followed looked hard at how long an evacuation really takes, and how little time there is when a cabin fills with smoke. Out of it came changes carried on aircraft still: floor-level lighting to mark the path to an exit when the air above is unbreathable, fire-blocking seat covers, and clearer access to the exits themselves, so that a row of seats does not stand between a passenger and the door.
I have read the report more than once. It is a careful document about a short span of time. Fifty-five people set out on a summer holiday flight and did not come home, and the safety card in the seat pocket in front of you is different because of them. The Wikipedia article is linked below.
The medical work that followed mattered a great deal. Post-mortem findings pointed to carbon monoxide and other combustion gases rather than burns, and later research showed that in dense smoke a person can be incapacitated within a minute or two, well before injury from heat. That is why the certification standard is framed in seconds, and why the lighting sits at floor level.
Harold, thank you for writing it plainly. The floor-proximity lighting came directly from the finding that smoke banks down from the ceiling, so the survivable air is low and people move on hands and knees; the strips are set low precisely so a crawling passenger can still see the way to a door.