CALCULATING THE ACCEPTANCE LEVELS

The acceptance level reflects the fact that people can live with the threat of fire up to a certain level, i.e. when the exposure to fire is limited. The exposure is linked to the presence of ignition sources, to egress conditions for people and to economical data for property and business.
A higher exposure results in a lower acceptance level. The Acceptance Levels are calculated with the activation factor a, the evacuation time factor t, the environment factor r and the dependency factor d. The activation factor a represents the presence of ignition sources, the environment factor r and the evacuation time factor t evaluate the egress conditions. The content factor c and the dependency factor d evaluate the economic data.

For property, the Acceptance Level A is defined as the maximum value 1.6 minus the activation factor a, the evacuation time factor t, and the value factor c.

For the occupants, the Acceptance Level A1 is defined as the maximum value 1.6 minus the activation factor a, the evacuation time factor t, and the environment factor r.

For the activities, the Acceptance Level A2 is defined as the maximum value 1.6 minus the activation factor a, the value factor c, the dependency factor d.

The activation factor a is defined through a review of possible fire sources, as a sum of all relevant values, referring to the following types of fire sources: Main activities, secondary activities, process and room heating systems, electrical Installations, presence of flammable gases, liquids and dusts. The "FRAME" calculation sheet provides lists and guidelines.

The evacuation time factor t is calculated by a formula including the dimensions of the compartment, the number of people, exit units and exit paths, and the mobility factor. "FRAME" allows also the use of an evacuation time defined by simulation or by evacuation drills. The formula used is:

The content factor c will evaluate the possibility to replace the building and its content, and the monetary value. The calculation allows for various currencies and building cost inflation.

The environment factor r will reflect the running speed of fire, and the dependency factor d will measure how much a business can be touched by fire.