Technical Booklet E Fire Safety·Page 13·0.2
Smoke control in escape routes
Early fire danger comes primarily from smoke and combustion products rather than flame. Means of escape provisions must include measures to limit smoke spread to protect occupants and maintain visibility of escape routes.
The primary danger in the early stages of a fire is not flame but smoke and other products of combustion which can directly affect the occupants of the building and obscure the escape routes. Measures designed to provide safe means of escape must therefore include provisions to limit the spread of smoke and other products of combustion.
Source — /Users/richardhill/Documents/planning-arch-project/data/documents/regional/Technical Booklet E - Fire Safety.pdf