"FRAME" is probably THE MOST COMPREHENSIVE , TRANSPARANT and PRACTICAL calculation method for fire risks in buildings. It is a tool to help a fire protection engineer to define a sufficient and cost effective fire safety concept for new or existing buildings. Unlike building codes that are mostly meant to assure a safe escape or rescue for the occupants, "FRAME" also aims at protecting the building, its content and the activities in it. This method can easily be used to evaluate fire risks in existing situations, and to find out whether alternative designs have also comparable efficiencies.

The "FRAME" method calculates the fire risk in buildings for the property and the content, for the occupants and for the activities in it. A systematic evaluation of all major influence factors is given, and the final result is a set of values which express in numbers, what otherwise has to be said by a long description of positive and negative aspects. The method is not suitable for open-air installations.


"FRAME" is developed from a method proposed by the Swiss engineer M. GRETENER in the early sixties, and from various other similar approaches such as: ERIC (Évaluation du Risque d’Incendie par le Calcul), a method developed in France by SARAT and CLUZEL; the German DIN 18230, the Austrian TRBV100, insurance rating systems, etc...

The GRETENER-method was originally made for the property fire risk. Some reports of fires with minor property damage but with fatalities indicated a need for a similar but distinct approach for human fire safety. Consequential loss or business interruption is a third aspect of fire risk that is considered in "FRAME", following the same reasoning as for the property and life safety.

The method is based on empirical formulas and a large professional experience of several persons. Although it is not possible to proof the method by actual fire tests, "FRAME" has been frequently checked on real case studies in the following ways:

  • a) For a series of buildings that are considered by experts to be well protected, the calculated values indicate also well protected buildings.
  • b) For a series of real building fires, which have been described in detail in the professional press, the calculated values indicate the same weak points that became evident by the real fires.
  • c) The balance of influence factors that is used in "FRAME" is comparable to what is found in most international fire codes.

After more than twenty years of application of the method, the author has hundreds of practical calculations to illustrate the use and effectiveness of the "FRAME"-method.

  • Designing good fire protection concepts

The first aim of "FRAME" is to guide a fire protection engineer to a balanced and well design fire protection concept. The experienced professional will "feel" the weak points as they show up during the calculation. Looking through the details will reveal the areas of possible improvement, and a new calculation can be made to get as final result: a well designed fire protection system.

  • Checking existing situations

"FRAME" is used to check an existing situation without any attempt to design improvements: the calculation will balance the weak points and the strong points and indicate how far the real situation is away from a good one.

"FRAME" can be used to demonstrate that fire protection that complies only with legal requirements for life safety can still result in inadequate protection for the building or the activities.

  • Loss estimates

Experience has shown that there is a relationship between the calculated Risk R and the amount of damage that can be expected after a serious fire situation. "FRAME" can thus be used to define "normal" loss expectancy. In some cases of abnormal high damage, it may trigger the quest for arson. In fact, where the difference between what can be expected under "normal" conditions and the real damage is high, some "help from the outside" is the most likely explanation.

  • Comparing the method with the building fire codes.

"FRAME" differs in some way from the approach of building codes. The method is conceived in such a way that the designer looks first for an adequate protection for the property before verifying life safety. In this way, he will check if additional protection is required for the occupants of an already well protected building. Codes and regulations limit often the theoretical possible choices to those construction methods that have built-in safety. Fire proofing for low hazard buildings can therefore be preferred to sprinklers, and is in most cases less expensive. However, "FRAME" make the balance between risk factors and protection in the same way as it is done in most fire codes.

  • Trade-offs.

Because of the careful built-in balance, "FRAME" can be used to check alternative designs or trade-offs in cases where older buildings are to be adapted to new requirements, but where the explicit rules ask for costly modifications. A first calculation shall be made for the building according to the rules to define the required level of protection, and a second calculation with the proposed trade-off will find out if the same or a lower risk level is obtained.

  • Quality control for the fire protection engineer

One of "FRAME"'s best applications is for self-control of the fire protection engineer: as the method requires a systematic review of most of the influence factors of a fire risk, it obliges the engineer to think in a professional way and it helps him to reduce the influence of subjective appreciation.


There are five basic ideas for the method:

  • 1.In an adequately protected building there is an equilibrium between the risk and the protection.

When both are expressed in numbers, one can say that the value of both must be equal, or that the quotient " risk divided by protection " is equal or smaller than 1. A higher value will indicate some lack of protection compared to the risk; a lower value represents a better situation.

The equilibrium between the fire risk and the fire protection that can be expected by "FRAME" is similar to what we may find "at home" in a modern non combustible house in an urban area: Property damage can be limited to the room of origin of a fire, there are no deaths, and life can be "back to normal" after a short period of time, necessary for clean-up and (temporary) repairs.

  • 2. The possible severity and the frequency of the risk can be expressed as the result of a number of influence factors.

A first set of influence factors will define numerical values for the worst cases, and these values will be named the Potential Risks, reflecting the severity.

A second set of values will define numerical values that measure the acceptability of a fire. The major factor is the probability of the fire, but the value of the contents, the circumstances of an evacuation; the economic importance will also be used to define how well the risk of a fire situation can be tolerated. These points will give the values of the Acceptance Levels.

  • 3. The level of fire protection can also be expressed as a combination of values for the different protection techniques. These values will represent the following elements:
  • -The most universal extinguishing agent: water
  • -The design of escapes routes
  • -The fire proofing of the construction
  • -The methods of detection and notification
  • -The manual fire fighting means
  • -The automatic fire extinguishing systems
  • -The public and private fire brigades
  • -The physical separation of risks
  • -The organisation for rescue and salvaging
  • 4. The risk assessment in a building is made separately for the property (building and content), for the occupants and for the activities in it.

These three calculations are necessary because the worst case will be different for buildings, persons or activities, as well as there are differences in the effectiveness of the protection.

- For the building and its content, total destruction is assumed to be the worst case.
- For the occupants, any beginning fire is already a threat and is therefore "the worst case".
- For the activities, a fire that damages everything, even without complete destruction is considered to be the most harmful.
  • 5. A separate calculation of the risk and the protection shall be made for each compartment.

Within one building several different situations can exist: For this reason, "FRAME" uses a one level fire compartment as the basic unit for the calculations. For multi-storey buildings, each level has to be considered separately. For buildings with more than one fire compartment, each compartment shall be reviewed on its own.


1. Building and content:

The Fire Risk R is defined as the quotient of the P

Potential Risk P by the Acceptance Level A and the Protection Level D

R = P / (A * D)

The Potential Risk P is defined as the product of the fire load factor q, the spread factor i, the area factor g, the level factor e, the venting factor v, and the access factor z.

P = q * i * g * e * v * z

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.

A = 1.6 - a - t - c

The Protection Level D is defined as the product of the water supply factor W, the normal protection factor N, the special protection factor S and the fire resistance factor F.

D = W * N * S * F

2. Occupants:

The Fire Risk R1 is defined as the quotient of the Potential Risk P1 by the Acceptance Level A1 and the Protection Level D1

R1 = P1/ (A1 * D1)

The Potential Risk P1 is defined as the product of the fire load factor q, the spread factor i, the level factor e, the venting factor v, and the access factor z.

P1 = q * i * e * v * z

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.

A1 = 1.6 - a - t - r

The Protection Level D1 is defined as the product of the normal protection factor N and the escape factor U.

D1 = N * U

3. Activities:

The Fire Risk R2 is defined as the quotient of the Potential Risk P2 by the Acceptance Level A2 and the Protection Level D2

R2 = P2 / ( A2 * D2)

The Potential Risk P2 is defined as the product of the spread factor i, the area factor g, the level factor e, the venting factor v, and the access factor z.

P2 = i * g * e * v * z

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.

A2 = 1.6 - a - c - d

The Protection Level D2 is defined as the product of the water supply factor W, the normal protection factor N, the special protection factor S and the salvage factor Y.

D2 = W * N * S * Y

These formulas show the similarity between the three parts of each calculation


The Potential Risks P, P1 and P2 are defined as products of the fire load factor q, the spread factor i, the area factor g, the level factor e, the venting factor v, and the access factor z.

The fire load factor q indicates how much can burn per area unit (m²). In practice, "FRAME" provides t tables with reasonable estimates of the values of Qi (fire load immobile) and Qm ( fire load mobile) based on building construction types and occupancy classification.

The fire spread factor i indicates how easy a fire can spread through a building. It is calculated from the average dimension of the content m, the flame propagation class M, and the destruction temperature T. "FRAME" gives guidelines how to define these parameters.

The area factor g indicates the horizontal influence of the fire. The factor g is calculated with the values of l, the theoretical length of the compartment, and of b, the equivalent width, expressed in meter. The length "l" of a compartment is the longest distance between the centres of two sides of the compartments’ perimeter. The equivalent width "b" is the quotient of the total area of the compartment by the theoretical length.

The level factor e indicates the vertical influence of the fire and will be calculated from the level number E. The main access level has number E = 0. Levels above the access are numbered 1, 2, 3, etc. Levels below the access level are numbered -1, -2, -3, etc.

The venting factor v indicates the influence of smoke and heat inside the building. It compares the venting capacity of the compartment with the sources of smoke

The access factor z indicates how difficult it is for outside help to get into the fire area.


The acceptance level reflects the fact that people can live with the threat of fire up to a certain level, as long as fire is an unlikely event, and as long as the consequences are not too irreversible.

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 only way to define the activation factor a is to go through a review of possible fire sources, and to sum 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 evacuation time factor t is calculated with the dimensions of the compartment, the number of people, exit units and exit paths, and the mobility factor.

Content factor c will evaluate the possibility to replace the building and its content, and the monetary value.

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.

"FRAME" calculates the Initial Risk Ro that indicates which level of protection can already be obtained from the built-in safety measures, such as compartimentation, risk separation, smoke venting, fire proofing, and give will a good guideline to choose an adequate fire protection system.


The protection levels are calculated with W, the water supply factor; N, the normal protection factor; S, the special protection factor; F, the fire resistance factor; U, the escape factor and Y, the salvage factor.

Water supply factor W considers the type and capacity of water storage and distribution network.

Normal protection factor N considers guard services, manual fire fighting, time delay of fire brigade intervention, personnel training.

Special Protection factor S considers automatic detection, reliability of water supplies, automatic protection, and fire brigade force.

Fire resistance factor F considers of the structural elements, outside walls, ceiling or roof and inner walls

Escape factor U considers every measure that speeds up the evacuation or slows down the early development of fire.

Salvage factor Y considers protection of critical items, and contingency planning.

All "FRAME" calculations and reports can be made with an EXCEL worksheet that is available in several languages: English, Dutch, French, German, Spanish and Portuguese.