"... it is usually the smoke that kills people, not the fire."
Approved Document B Volume 1, 2019 edition Section B1 states:
In the Secretary of State’s view, requirement B1 is met by achieving all of the following:
- There are sufficient means for giving early warning of fire to people in the building.
- All people can escape to a place of safety without external assistance.
- Escape routes are suitably located, sufficient in number and of adequate capacity.
- Where necessary, escape routes are sufficiently protected from the effects of fire and smoke.
- Escape routes are adequately lit and exits are suitably signed.
- There are appropriate provisions to limit the ingress of smoke to the escape routes, or to restrict the spread of fire and remove smoke.
- For buildings containing flats, there are appropriate provisions to support a stay put evacuation strategy.
The extent to which any of these measures are necessary is dependent on the use of the building, its size and its height.
Building work and material changes of use subject to requirement B1 include both new and existing buildings.