fire - egress

8/13/2019 Fire - Egress

1/28

CHAPTER 1. Literature review


2/28


3/28

The variables that help to determine the most appropriate technology of life safety for a

particular situation and about escape route definitions and its components & principles of design

is briefly discussed in the book A complete guide to Fire & Buildings (ERIC.W.Marchant,

1972). He discusses on some aspects of building design and their influence on the rescue of

people in building fires and of the main techniques of rescue. Some case studies are included to

illustrate some of the dangers inherent in common types of buildings. Author brings into light,

more concepts of importance to life safety, like smoke load and enabling of smoke control

techniques and some of the problems of smoke control in tall buildings are also discussed.

1.2.2 Identification of means of egress componentsBukowski.R.W.(2008), documented current regulatory requirements for means of

egress in fires, their origins and scientific basis, and the approaches used in US and in other

countries, along with a review of the international code requirements for egress stairs. Author

also explains on the scientific study of exit width based on ergonomics and the studies on the

earliest of stair geometry. The paper questions the adequacy of the basic 22 inch dimensionsbeing used, owing to the increasing size and weight of a typical person especially in US. It also

explains studies in tread geometry conducted by an architect in France named Francois Blondel

and also reviews international code requirements for egress stairs. Where stairs are the primary

means of vertical egress in fires and other emergencies such stairs shall be a minimum width of

1400 mm (56 in). Where protected elevators are provided as the primary means of vertical egress

in fires and other emergencies stairs shall be a minimum width of 1100 mm (44 in).

Bukowski.R.W.(2008), in his paper throws light to the importance of incorporation of refuge

floors in tall buildings in Asia. Horizontal transfer corridors designed as means of egress

components shall be provided every 25 floors (generally on mechanical floors) to link all egressstairs and to provide the ability to safely move between stairs.

Shimshoni 2007( cited in Collier.P.C.R, 2008) study shows that exit stairways wider than both

the required 1120 mm and 1420 mm proposed for the NFPA documents are already being

designed into major high-rise buildings. Designers are cautioned however, not to make the clear

width between handrails larger than 1525 mm as extensive crowd use puts people in the middle

of the stair beyond the reach of a handrail. Thus, 1725 mm is the largest nominal width

recommended for exit stairways. Wide stairs of 1725 mm provide more people flow per width

than narrower stairs. For example, a 1420 mm nominal width stair performs about 38% more

effectivelyfor flowthan a traditional 1120 mm nominal width stair even though the former is

only 27% wider (Collier.P.C.R, 2008).

1.2.3 Principles of evacuation time and travel distanceCollier.P.C.R.(2008) in his study has demonstrated that with the changed demographics of the

worldwide population, people have increased in size considerably in the period since provisions

for egress and minimum exit widths were implemented for buildings and assembly areas on the

basis of contemporary population mobility studies. The current situation is that the existing


4/28

egress provisions are unlikely to deliver the evacuation times required by fire safety designs.

Suggested means of correcting this potentially serious shortfall in egress capacity go beyond the

obvious solution of simply increasing exit widths which, apart from new buildings, would be

considered uneconomic and impractical. His study reviews the existing minimum exit width

requirements in the New Zealand Building Code (NZBC) Compliance Document C/AS1 (DBH

2005) prompted by a recent paper by Fruin and Pauls (2007) expressing concern about current

practices. The study focuses on cultural, anthropometric and mobility differences internationally,

and with time the impact on the specification of minimum exit widths needed for emergency

egress.

Life safety features (United States Fire administration) describes the emergency evacuation plans

and the purpose of it. The evacuation plan is tied directly to fire drills, which must occur in such

occupancy on a regular basis; the building manager or owner should keep records to show

compliance. Many fire departments hold open houses at their stations some time during National

Fire Prevention Week, which is an excellent time to provide home fire safety information, but it

takes place only once a year; fire safety must be presented on a continuing, year-round basis.

Whereas Schanchenmayr.M.P., Quade.P.B & Douglas, (sep.1998) in their paper studies the

evacuation requirements for train ways alone, addresses the train way egress requirements and

provide recommendations and general guidelines for the application of the NFPA 130 egress

element for a broader range of transit systems and modes, including commuter rail and light rail

transit stations.

1.2.4 Role of elevators in modern means of egressBukowski.R.W.(2008), emphasizes on the use of Protected Occupant Egress Elevators Where

required, all elevators except any designated fire service elevator(s) shall be designed andarranged to permit their safe use for occupant evacuation. These occupant elevators shall be

powered by normal and emergency power, with both power and control wiring protected by fire

resistant construction at least equal to the fire resistance requirement applicable to the primary

structural frame. Occupant egress elevators shall operate in a hoistway protected from the

adverse effects of water and opening into a protected lobby on each floor that serves as an area of

refuge while awaiting the elevator.

Bukowski, 2007( as cited in Collier.P.C.R.,2008) wrote in response to the potential need for

more timely evacuation of occupants in tall buildings that new provisions allowing the use of

elevators in certain situations prior to Phase I Emergency Recall Operation (as mandated by the

Firefighters Emergency Operation provision of ASME A17.1 Safety Code for Elevators andEscalators) be put forward. Elevators remain usable after initiation of the building fire alarm

system, provided that the elevators have not been recalled upon detection of smoke in the

elevator lobbies, machine room or hoist ways. In such situations the elevators remain operable

and are available for occupant evacuation. Similarly a new standard is proposed (ISO 2006) that

suggests new technologies and strategies for evacuations using elevators coupled with means

of providing information to people (evacuees) to make correct decisions in their use.


5/28

1.2.5 Studies on density and flow rateRoytman.M.Ya, (1969) in his book describes about the distinctive features of the movement of

people during emergency evacuation and stages of evacuation, with brief descriptions on various

terms & standards to be followed in Evacuation exits and routes. Approximate methods for

calculating the permissible and actual evacuation times and building design requirements for safeevacuation of people are described. According to him the parameters characteristic of the

movement of people include streams of people, width of streams, densities of streams of people,

length of stride, speed of motion and traffic clearing capacity of an exit.

Bukowski.R.W (2008), in his paper says that 1935 NBS report clearly stated the correlation

between width and flow. The committee (Bukowski.R.W.,2008)agreed that, rates of 45

persons per 22-inch unit per minute for travel down stairways, and 60 persons per 22-inch unit

per minute through doorways, which had been in use on the basis of earlier observations, were

sufficiently confirmed to warrant their retention in connection with the requirements under

development. Paper also describes about effective space requirement and the concepts ofeffective width of a stair, as discussed by Pauls and Fruin in their publishing.

Fruin and Pauls (2007) draw attention to concerns about current practices and methods of

calculating egress capacity. In particular, they suggested that recent and ongoing demographic

changes in the population warrant reconsideration of the long accepted and established beliefs,

data and formulae that are the basis for design requirements in codes, standards and handbooks

which are used for performance predictions affecting life safety in existing and proposed

facilities. The basis of the established calculation methods subject to change are:

Human body mass and sizes have increased significantly since the 1960s. The original basis used for determining the movement characteristics of the general

population is not universally applicable. Studies of the movement of relatively fit

commuter people that were used to measure egress characteristics may not be applicable

to the general population who may not, on average, be so physically able.

1.2.6 Methods for analysis of means of egressAccording to Bukowski.R.W.(2008), in the U.S., Australia and Japan, the design of egress

systems are based on the population of the largest, single floor. In U.K., Spain, and China the

number of floors served by the stair impacts the total number of people served by a stair of a

given width. Yet in any performance analysis of an egress system in these or other countries,

(Design and Construction of Building exits, 1935)regulators require a timed egress analysis to

estimate Required Safe Egress Time (RSET) which is compared against Available Safe Egress

Time (ASET). ASET is generally determined by fire modeling to estimate conditions in the

egress path that might lead to injury or death.


6/28

Averill.J.D., Reneke.P. and Peacock.R.D, (2007), study identifies sources of uncertainty in

RSET (required safe egress time) calculations, with focus on data and modeling. A model for

efficiently calculating the range of egress solutions for a particular design is presented. The

importance of the two central concepts of performance-based design, ASET (available safe

egress time) and RSET (required safe egress time to achieve performance objectives. The

limitations in quantity and quality in existing data sets for model inputs are validated. The paper

sets out definite explanations for egress model theory with examples. The paper brings out three

recommendations for future research. First, future data collections and model inputs should

utilize distributions. Second, future data collections should focus on emergency evacuation data

rather than fire drill data. Finally, modeling output should utilize cumulative distribution

functions to visualize the range of egress solutions. (Bukowski.R.W., 2008)

1.2.7 Occupant load and its calculationsBukowski.R.W.(2008), in his studies explains why the US designs exits for capacity and why

the capacity is based on the population of a single floor. The building regulations from variouscountries and the methods used for egress is summarized and the factors influencing

characteristics of egress stair design like minimum number of egress stairs provided, maximum

travel distance to a stair, width of doors and passageways, interior finish, headroom, handrails etc

are also discussed.

Muha.T, 2012, in his research project Evaluating Occupant Load Factors for Business

Operations recommends i) an increase in the value of the occupant load factor for general

business use in the Life Safety Code from 100 ft2/person to 150ft2/person, and ii) a new

category of business use in the form of high density business use spaces, such as call centers.

This study investigates the origins of the 100ft2/person factor, previous occupant load studies,

changes in office space planning and use, availability of office furnishings, and current officeoccupant load preferences, then recommends alternate occupant load factors and business use

categories.

Life safety features, discusses on the factors that determine occupant load, and how occupant

load will determine the number of exits required from a room or building and their total width.

Paper also explains on the method of calculating net and gross floor area for buildings with

examples and also cited occupant load calculation examples.

1.2.8

Special requirements for healthcare and mass transit terminalsApplication Guidelines for the Egress Element of the Fire Protection Standard for Fixed

Guideway Transit Systems (Schanchenmayr.M.P., Quade.P.B & Douglas, sep.1998)reviews The

theoretical concepts that underlie the egress requirements supports a more enlightened

application of the NFPA 130 Standard, particularly in non-conventional settings. The NFPA 130

egress element is placed in a broader context in order to illustrate the overall intent of the egress

requirements as well as their consistency with, and departure from, model building codes.


7/28

Schanchenmayr.M.P., Quade.P.B & Douglas, (sep.1998) throws light into the following

concerns:

Insufficient industry understanding of NFPA 130 emergency egress element. The definitions, instructions, and sample calculations published with the NFPA 130

Standard do not adequately guide practitioners and have led to inconsistent application of

the NFPA 130 egress element, potentially leading to overly conservative design solutions

or to inadequate designs that are extremely costly to remedy retroactively.

Although the NFPA 130 Standard technically addresses only rail rapid transit modes anddoes not cover requirements for ... passenger railroad systems including those which

provide commuter services. Despite this widespread practice, no guidance is offered for

the application of the NFPA 130 Standard for non-rapid transit systems and facilities

The NFPA 130 Standard contains minimum design criteria with regard to emergencyegress only; however, in the absence of standard specifications for transit stations,

designers frequently view the NFPA 130 requirements as the principal design guidelines

for transit stations. This application often occurs without sufficient understanding of the

relationship between the NFPA 130 Standard and the underlying requirements of the

NFPA 101 Code.

The book provides an overview and detailed technical discussion of the NFPA 130 egress

requirements as they apply to transit stations, evacuation requirements for train ways, application

guidelines and sample calculations.

1.2.9 Social behaviors in emergency situationsChu and Law (2012), in their paper A Computational Framework Incorporating Human

Behaviors for Egress Simulation talks about a comprehensive review of various social theories

about crowd behaviors. Social scientists and disaster management researchers have been

studying human behaviors in emergency situations and have developed a variety of theories

about crowd behaviors in emergency situations. Examples of prevalent theories on crowd

behaviors include the panic theory (Le Bon, 1960), the decision-making theory (Mintz, 1951),

the normative theory (Aguirre et al., 2011; McPhail, 1991; Turner and Killian, 1987), the

affiliative theory (Mawson, 2005; Sime, 1983), and the place script theory (Donald and Canter,

1990). Earlier theories in crowd behavior suggest that people tend to behave individually and

show non-adaptive behaviors in dangerous situations. For example, the panic theory suggests

that people become panicked in an emergency situation and act irrationally. In contrast, the

decision-making theory argues that people act rationally to achieve a better outcome in the

situation. Recent theories, on the other hand, emphasize the sociality of the crowd (such as pre


8/28

existing social relationships or emerging identity during an emergency situation) in explaining

the occupants reactions in past accidents.

Different social theories explain human behaviors in emergencies using different mechanisms

and variables. In order to systematically study different social theories and incorporate them

into a computational framework, we classify the theories into three behavior categories; namely,

individual, group, and crowd. As is evidenced from the selected prevailing social theories on

human behaviors, social characteristics of individuals play an important role in determining their

behaviors during emergencies. It is conjectured that human behaviors in egress is influenced at

three levels: individual experience, social group, and crowd interactions. The staged

representation of social effects forms the basis in the design of our egress simulation

framework.(Chu and Law, 2012)

Hoskin, (2004) investigated emergency egress considerations of stadia by examining occupant

characteristics and discussing how effective crowd management can be used to improve

evacuation procedures in his paper Crowd characteristics and egress at Stadia. The findings are

based on recent research on fire protection and evacuation procedures of stadia venues primarily

in New Zealand. To the authors knowledge the research that this paper is based on is the sum

total of high density crowd egress studies performed on the New Zealand populous, in order to

test the appropriateness of recommended occupant densities used to calculate egress capacities

for such venues in New Zealand. Hoskin also discusses about the potential components of a

stadium evacuation that differs from normal egress.

Safe egress is one of the key design issues identified by facility planners, manager and

inspectors. Computational tools are now available for the simulation and design of emergency

evacuation and egress. However, these tools rely heavily on assumptions about human individual

and social behaviors, which have been found to be oversimplified, inconsistent and even

incorrect. Furthermore, the behaviors are usually incorporated into the computational model in

an ad hoc manner. Xiaoshan.P et al., (2004) presents a framework for studying human and social

behavior from the perspectives of human decision-making and social interaction and to

incorporate such behavior systematically in a dynamic computational model suitable for

emergency egress analysis through his paper on Human and Social Behavior in Computational

Modeling and Analysis of Egress.

Xiaoshan.P et al., (2004) , in their study discusses briefly on the topics - human and social

behavior and crowd dynamics, Non-adaptive crowd behavior (According to the author existing

theories on crowd behavior in emergency situation can be classified into three basic categories:

(1) panic , (2) decision-making , and (3) urgency levels. ), Computational models etc. According

to the author Social behaviors are complex phenomena emerged from the interactions among a

group of autonomous agents. The paper describes that the prototype system can demonstrate


9/28

social emergent phenomena including competitive, queuing, and herding behaviors, and bi-

directional crowd flow.

1.2.10 Egress simulation models and human behavior modelingGrosshandler et al., 2005 (As mentioned in Chu and Law (2012)) describes the system

framework and the features currently incorporated in the prototype, through implementing

several well-studied social behaviors in the prototype model, and study the effects of such social

behaviors on an evacuation scenario based on the historical fire accident at the Station Nightclub

in Warwick, Rhode Island.

In their paper Chu and Law (2012), describes the basic framework and the implementation of

several social behaviors, which are based on recent social science studies about human response

in emergency situations. Simulation results from the prototype reveals that social behaviors

exhibited by the evacuating crowd can lead to changes in the overall egress time and pattern. By

representing the virtual agents and the environment specific to evacuation situation, the researchaddresses the issues in incorporating human and social behaviors in egress simulation.

In this paper, Chu and Law have described an ongoing research effort in developing a modular

and flexible computational framework to incorporate human and social behavioral models for

egress simulations. In the following, they discuss the results for possible effects of social

behaviors on evacuation and then an overall framework for the multi-agent based simulation

system. The three most common approaches based on the systems virtual representation of the

building environment and the occupants are the particle systems, cellular automata and agent-

based systems.

Due to the high variability of human behaviors in different situations, a single

behavioral theory may not be sufficient to explain the response of people in differentemergency scenarios. A flexible simulation platform, which can account for various

social theories in different emergency scenarios, is therefore desirable. The ability to

model social behavioral theories in a computational program not only provides more

realistic simulation results, but also provides a means to test and validate the

corresponding behavioral theories.(Chu and Law, 2012)

Xiaoshan.P et al., (2004) through their paper, presented a crowd simulation model that takes

into account human and social behavior. According to them the three main reasons for

developing computer simulation for crowd behaviors: 1) to test scientific theories and

hypotheses; 2) to test design strategies; 3) to create phenomena about which to theorize. Each

crowd setting (i.e., crowd attributes and physical environment) is unique. A full understanding of

non adaptive crowd behaviors normally requires exposing real people to the specific

environment for obtaining empirical data, which is difficult since such environments are often

dangerous in nature. In addition to study crowd behavior based on observations and historical

records, computer simulation is a useful alternative that can provide valuable information to

evaluate a design, to help planning process, and for dealing with emergencies.


10/28

1.3 SummaryThis chapter gives a list of literature that is available and will be used in the seminar. The

literature has been divided into various topics and in each topic, the corresponding literatureavailable have been discussed.

The salient points that have been covered in literature, is further discussed on each chapters and

its sub sections. The study on literature has helped in formulating survey and in supporting the

case studies.


11/28

CHAPTER 2. Components of means of egress and their planning principles2.1 Means of egress

Means of egress is a continuous and unobstructed way of travel from any point in a building or

structure to a place of comparative safety.An exit may be a doorway; corridor, passageway(s) to

an internal staircase, or external staircase, or to a VERANDAH or terrace(s), which have access to

the street, or to the roof of a building or a refuge area. An exit may also include a horizontal exit

leading to an adjoining building at the same level. Lifts and escalators shall not be considered as

exits. Every exit, exit access or exit discharge shall be continuously maintained free of all

obstructions or impediments to full use in the case of fire or other emergency.

2.1.1

Components: Exit, Exit access, Exit door, Exit dischargeExitis that portion of a means of egress that is separated from all other spaces of a building or

structure by construction or equipment as required to provide a protected way of travel to the exit

discharge. A Horizontal Exit is a way of passage from one building to an area of refuge in

another building on approximately the same level, or a way of passage through or around a fire

barrier to an area of refuge on approximately the same level in the same building that affords

safety from fire and smoke originating from the area of incidence and areas communicating

therewith.

Exit Access isthat portion of a means of egress that leads to an exit and Exit Dischargeis that

portion of a means of egress between the termination of an exit and a public way. A door or

access point along the path of egress travel from an occupied room, area or space where the path

of egress enters an intervening room, corridor, unenclosed exit access stair or unenclosed exit

access ramp, is termed as Exit access door.

2.1.2 Common path of travelThe common path of egress travel, or CPET, is defined in the IBC as: That portion of exit

access which the occupants are required to traverse before two separate and distinct paths of

egress travel to two exits are available. Paths that merge are common paths of travel. Common

paths of egress travel shall be included within the permitted travel distance.


12/28

Common Path of Travel is that portion of exit access that must be traversed before two separate

and distinct paths of travel to two exits are available. A common path of travel shall be permitted

for the first 20 ft (6100 mm) from any point where the common path serves any number of

occupants, and for the first 75 ft (23 m) from any point where the common path serves not more

than 50 occupants.Dead-end corridors shall not exceed 20 ft (6100 mm). Common path of travel

shall not exceed 100 ft (30 m) in a building protected throughout by an approved, supervised

automatic sprinkler system. Common path of travel shall not exceed 75 ft (23 m) in a building

not protected throughout by an approved, supervised automatic sprinkler system.[NFPA]

2.1.1 Common path of egress travel

2.1.3 Travel distanceThe distance to be travelled from any point in a building to a protected escape route, external

escape route or final exit (NFPA). Although not specifically defined in the International Building

Code (IBC), travel distance is described in Section 1016.1 (2009 IBC) as, the maximum length

of exit access travel, measured from the most remote point within a story along the natural and

unobstructed path of egress travel to an exterior exit door at the level of exit discharge, an

entrance to a vertical exit enclosure, an exit passageway, a horizontal exit, an exterior exit

stairway or an exterior exit ramp, [which] shall not exceed the distances given in Table 1016.1.

(Ronald L. Geren, 2009)

In essence, it is the total distance an occupant must cover to reach an exit as defined by the IBC

(See Figure). The concern with travel distance is to ensure that occupants can reach an exterior


13/28

door or protected exit enclosure without having to take an extremely long path to get there, thus

reducing the occupants exposure to a potential hazard.(Ronald L. Geren, 2009)

2.1.2 Determining travel distance

Table 1016.1 provides the limitations on travel distance based on occupancy and the installation

of a sprinkler system. For most non-sprinklered occupancy groups, this distance is 200 feet. With

a sprinkler system installed, this distance increases to 250 feet, but for B occupancies, it

increases to 300 feet. Non-sprinklered Groups F-2, S- 2, and U are limited to 300 feet (400 feet

when sprinklered). Group I and H occupancies have various travel distances listed, but are

limited to only sprinklered buildings, since these occupancies are required to be sprinklered.

(Ronald L. Geren, 2009)

According to NBC, Exits shall be so located that the travel, distance on the floor shall not exceed

the distance given in Table 22. The travel distance to an exit from the dead end of a corridor shall

not exceed half the distance specified in Table 22, except in assembly and institutional

occupancies in which case it shall not exceed 6 m. Whenever more than one exit is required for

any room space or floor of a building, exits shall be placed as remote from each other as possible

and shall be arranged to provide direct access in separate directions from any point in the area

served.


14/28

NFPA 101 states, the travel distance to an exit shall be measured on the floor or other walking

surface as follows:

(1) Along the centerline of the natural path of travel, starting from the most remote point subject

to occupancy

(2) Curving around any corners or obstructions, with a 12 in. (305 mm) clearance there from

(3) Terminating at one of the following:

(a) Center of the doorway

(b) Other point at which the exit begins

(c) Smoke barrier in an existing detention and correctional occupancy


15/28

2.2 Minimum width & Clear widthAccording to NFPA, The width of an exit passageway shall be sized to accommodate the

aggregate required capacity of all exits that discharge through it, unless one of the following

conditions applies, Where an exit passageway serves occupants of the level of exit discharge as

well as other stories, the capacity shall not be required to be aggregated.

In new construction, the minimum width of any exit passageway into which an exit stair

discharges, or that serves as a horizontal transfer within an exit stair system, shall meet the

following criteria:

(1) The minimum width of the exit passageway shall be not less than two-thirds of the width of

the exit stair.

(2) Where stairs are credited with egress capacity in accordance with 7.3.3.2, the exit

passageway width shall be sized to accommodate the same capacity as the stair, with such

capacity determined by use of the capacity factors in Table 7.3.3.1.

NBC, states that all required exits that serve as egress from hospital or infirmary sections shall be

not less than 2 m in clear width including patient bedroom doors to permit transportation of

patients on beds, litters, or mattresses. The minimum width of corridors serving patients

bedrooms in buildings shall be 2400 mm. For detailed information on recommendations for

buildings and facilities for the physically handicapped, reference may be made to good practice

2.3 Staircases2.3.1 Staircase construction

All buildings, which are 15 m in height or above, and all buildings used as educational,

assembly, institutional, industrial, storage, and hazardous occupancies and mixed occupancies

with any of the aforesaid occupancies, having area more than 500 m2 on each floor shall have a

minimum of two staircases. They shall be of enclosed type; at least one of them shall be on

external walls of buildings and shall open directly to the exterior, interior open space or to an

open place of safety. Further, the provision or otherwise of alternative staircases shall be subject

to the requirements of travel distance being complied with.


16/28

2.3.1.1 Internal staircasesInternal stairs shall be constructed as a self contained unit with an external wall of the building

constituting at least one of its sides and shall be completely enclosed. A staircase shall not be

arranged round a lift shaft.Hollow combustible construction shall not be permitted.

2.3.1.2 External staircasesAn external staircase is desirable to be provided for high rise buildings. External stairs, when

provided shall always be kept in sound operable conditions. All external stairs shall be directly

connected to the ground. The route to the external stairs shall be free of obstructions at all times.

Entrance to the external stairs shall be separate and remote from the internal staircase. No

external staircase, used as a fire escape, shall be inclined at an angle greater than 45 from the

horizontal.

2.3.1.3 Codal provisions on staircasesN

o: FEATURES INTERNAL STAIRCASE EXTERNAL STAIRCASE

1Material of

construction

Shall be constructed ofnoncombustible materials

throughout.

No combustible material shall be

used for decoration/wall panelingin the staircase.

The external stairs shall be constructed

of noncombustible materials, and any

doorway leading to it shall have therequired fire resistance.

Unprotected steel frame staircase will

not be

accepted as means of escape. However,steel staircase

in an enclosed fire rated compartment

of 2 h will be accepted as means of

escape.

2 Minimum width

External stairs shall have straight flight

not less

than 1250 mm wideThe use of spiral staircase shall be

limited to low occupant load and to abuilding not exceeding 9 m

in height. A spiral stair case shall be not

less than 1500 mm in diameter and shall

be designed to give adequateheadroom.


17/28

3 Stair dimensions

The minimum width of treadwithout nosing

shall be 250 mm for internalstaircase of residential buildings.

This shall be 300 mm for

assembly, hotels, educational,institutional, business and otherbuildings. The treads shall be

constructed and maintained in a

manner to prevent slipping.

External stairs shall have 250 mm

treads

The maximum height of riser shall

be 190 mmfor residential buildings and 150

mm for other buildings and the

number shall be limited to 15 per

flight.

The maximum height of risers shall berisers

not more than 190 mm. The number of

risers shall be

limited to 15 per flight.

5 Mid- Landing

The minimum headroom in apassage underthe landing of a staircase and under

the staircase shall be 2.2 m.

All landings of floor shall havefloor indicating boards prominently

indicating the number of floor as

per bye-laws.

6 Handrail

Handrails shall be provided at a

height of

1000 mm to be measured from the

base of the middle of the treads to

the top of the handrails.Balusters/railing shall be provided

such that the width of staircasedoes not reduce

Handrails shall be of a height not less

than

1000 mm and not exceeding 1200 mm.

There shallbe provisions of balusters with

maximum gap of150 mm.

8Openings into

staircases

Care shall be taken to ensure that nowall

opening or window opens onto or close

to an external


18/28

stairs.

9

Entry to staircase (

Door , Direction of

opening, Entrancelobby)

No living space, store or other firerisk shall

open directly into the staircase orstaircases.

Entrance to the external stairs shall be

separateand remote from the internal staircase.

External exit door of staircase

enclosure atground level shall opendirectly to the openspaces or

through a large lobby, if necessary.

The main and external staircasesshall be

continuous from ground floor to

the terracelevel.

2.3.2 Pressurization of staircasesThough in normal building design, compartmentation plays a vital part in limiting the spread of

fire, smoke will readily spread to adjacent spaces through the various leakage openings in the

compartment enclosure, such as cracks, openings around pipes ducts, airflow grills and doors, as

perfect sealing of all these openings is not possible. It is smoke and toxic gases, rather than

flame, that will initially obstruct the free movement of occupants of the building through the

means of escape (escape routes). Hence the exclusion of smoke and toxic gases from the

protected routes is of great importance.

Pressurization is a method adopted for protected escape routes against ingress of smoke,

especially in high-rise buildings. In pressurization, air is injected into the staircases, lobbies or

corridors, to raise their pressure slightly above the pressure in adjacent parts of the building. As a

result, ingress of smoke or toxic gases into the escape routes will be prevented. The

pressurization of staircases shall be adopted for high rise buildings and building having mixed

occupancy/ multiplexes having covered area more than 500 m2. The pressure difference for

staircases shall be as under:


19/28

If possible, the same levels shall be used for lobbies and corridors, but levels slightly lower may

be used for these spaces if desired. The difference in pressurization levels between staircase and

lobbies (or corridors) shall not be greater than 5 Pa. Pressurization system may be of two types:

a) Single-stage, designed for operation only in the event of an emergency, and

b) Two-stage, where normally a level of pressurization is maintained in the protected escape

routes and an increased level of pressurization can be brought into operation in an emergency.

2.4 RampRamps shall comply with all the applicable requirements for stairways regarding enclosure,

capacity and limiting dimensions except for special uses and occupancies. The slope of a ramp

shall not exceed 1 in 10. In certain cases steeper slopes maybe permitted but in no case greater

than 1 in 8. For all slopes exceeding 1 in 10 and wherever the use is such as to involve danger of

slipping, the ramp shall be surfaced with approved non-slipping material.

2.5 Fire TowerFire towers are the preferred type of escape route for storeyed buildings and these shall be

considered as the safest route for escape. Their number, location and size shall depend on the

building concerned, and its associated escape routes. In high rise buildings with over 8 storeys or

24 m in height, at least one required means of egress shall preferably be a fire tower. The fire

towers shall be constructed of walls with a 2 h fire resistance rating without openings other than

the exit doorways, with platforms, landings and balconies having the same fire-resistance rating.


20/28

2.6 Occupant loadOccupant Load is for determining the exits required, the number of persons within any floor area

or the occupant load shall be based on the actual number of occupants, but in no case less than

that specified in Table 20, NBC. Occupant load in dormitory portions of homes for the aged,

orphanages, insane asylums, etc, where sleeping accommodation is provided, shall be calculated

at not less than 7.5 m2 gross floor area/person. The gross floor area shall include, in addition to

the main assembly room or space, any occupied connecting room or space in the same storey or

in the storeys above or below, where entrance is common to such rooms and spaces and they are

Available for use by the occupants of the assembly place. No deductions shall be made in the

gross area for corridors, closets or other sub-divisions; the area shall include all space serving the

particular assembly occupancy.


21/28

2.7 Occupant load of mezzanine floorThe occupant load of a mezzanine floor discharging to a floor below shall be added to that floor

occupancy and the capacity of the exits shall be designed for the total occupancy load thus

established.

2.8 Number of occupants per unit widthOccupants per unit exit width shall be in accordance with Table 21, NBC 2005


22/28

2.9 Capacity of egress elements2.9.1 Capacity of exit door

Size of the exit door of exit way should be calculated accordingly keeping in view the travel

distance as per Table 22 of NBC.

2.9.2 Capacity of exit accessThe unit of exit width, used to measure the capacity of any exit, shall be 500 mm. A clear width

of 250 mm shall be counted as an additional half unit. Clear widths less than 250 mm shall not be

counted for exit width. Occupants per unit exit width shall be in accordance with Table 21 of

NBC

2.9.3 Capacity of exit dischargeDischarge through Areas on Level of Exit Discharge shall not more than 50 percent of the

required number of exits, and not more than 50 percent of the required egress capacity, shall

discharge through areas on the level of exit discharge, unless otherwise permitted in 7.7.2.1 and

7.7.2.2 and provided that the criteria of 7.7.2.3 through 7.7.2.7 also are met.

7.7.2.1 One hundred percent of the exits shall be permitted to discharge through areas on the

level of exit discharge in detention and correctional occupancies

7.7.2.2 In existing buildings, the 50 percent limit on egress capacity shall not apply if the 50

percent limit on the required number of exits is met.

7.7.2.3 The discharge specified in 7.7.2 shall lead to a free and unobstructed way to the exterior

of the building, and such way shall be readily visible and identifiable from the point of discharge

from the exit.

7.7.2.4 The level of discharge shall be protected throughout by an approved automatic sprinkler

system in accordance with, or the portion of the level of discharge used for discharge shall be

protected by an approved automatic sprinkler system in accordance with Section 9.7 and shall be

separated from the non-sprinklered portion of the floor by a fire resistance rating meeting the

requirements for the enclosure of exits.


23/28

The requirement of 7.7.2.4 shall not apply where the discharge area is a vestibule or foyer that

meets all of the following criteria:

(1) The depth from the exterior of the building shall be not more than 10 ft (3050 mm), and the

length shall be not more than 30 ft (9140 mm).

(2) The foyer shall be separated from the remainder of the level of discharge by construction

providing protection not less than the equivalent of wired glass in steel frames.

(3) The foyer shall serve only as means of egress and shall include an exit directly to the outside.

2.9.4 Capacity of staircasesThe effective capacity of stairways has been shown by research to be proportional to the

effective width of the stairway, which is the nominal width minus 12 in. (305 mm). This

phenomenon, and the supporting research, were described in the chapter, Movement of People,

in the first, second, and third editions of the SFPE Handbook of Fire Protection Engineering and

was also addressed in Appendix D of the 1985 edition of NFPA 101, among several other

publications. In 1988, this appendix was moved to form Chapter 2 of the 1988 edition of NFPA

101M, Alternative Approaches to Life Safety. (This document was later designated as NFPA

101A, Guide on Alternative Approaches to Life Safety, and this chapter remained in thedocument through the 1998 edition.) In essence, the effective width phenomenon recognizes that

there is an edge or boundary effect at the sides of a circulation path. It has been best examined in

relation to stairway width, where the edge effect was estimated to be 6 in. (150 mm) on each

side, but a similar phenomenon occurs with other paths, such as corridors and doors, although

quantitative estimates of their edge effect are not as well established as they have been for

stairways, at least those stairways studied in Canada during the late 1960s through the 1970s in

office building evacuation drills and in crowd movement in a variety of buildings with assembly

occupancy.

More recent studies have not been performed to determine how the edge effect might be

changing (or has changed) with demographic changes to larger, heavier occupants moving more

slowly, and thus swaying laterally, to maintain balance when walking. The impact of such


24/28

demographic changes, which are significant and influential for evacuation flow and speed of

movement on stairs, for example, has the effect of increasing the time of evacuation in a way that

affects all stair widths, but will be most pronounced for nominal widths less than 56 in. (1422

mm).

Without taking into account occupant demographic changes in the last few decades that affect

evacuation performance, especially on stairs, the formula for enhanced capacity of stairways

wider than 44 in. (1120 mm) assumes that any portion of the nominal width greater than 44 in.

(1120 mm) is as effective proportionally as the effective width of a nominal 44 in. (1120 mm)

stair, that is, 32 in. (810 mm). Thus, the denominator (0.218) in the equation is simply the

effective width of 32 in. (810 mm) divided by the capacity of 147 persons that is credited, by the

0.3 in. (7.6 mm) capacity factor in Table 7.3.3.1, to the corresponding nominal width, 44 in.

(1120 mm). The resulting permitted stairway capacities, based on occupant load of single stories

(in accordance with 7.3.1.4), for several stairway widths are shown in Table below.

2.10 Exit access ventilation2.10.1 Natural ventilation2.10.2 Mechanical ventilation

2.11 Exit Discharge Lobby2.12 Exit marking

The exit sign with arrow indicating the way to the escape route shall be provided at a suitable

height from the floor level on the wall and shall be illuminated by electric light connected to


25/28

corridor circuits. All exit way marking signs should be flush with the wall and so designed that

no mechanical damage shall occur to them due to moving of furniture or other heavy

equipments. Further, all landings of floor shall have floor indicating boards prominently

indicating the number of floor as per bye-laws.

The floor indication board shall be placed on the wall immediately facing the flight of stairs and

nearest to the landing. It shall be of size not less than 0.5 m x 0.5 m.

2.12.1 Type2.12.2 Size2.12.3 Placement

2.13 IlluminationThat part of emergency lighting which is provided to ensure that the escape route is illuminated

at all material times, for example, at all times when persons are on the premises, or at times the

main lighting is not available, either for the whole building or for the escape routes.

The floors of areas covered for the means of exit shall be illuminated to values not less than 1 ft

candle (10 LUX) at floor level. In auditoriums, theatres, concert halls and such other places of

assembly, the illumination of floor exit/access maybe reduced during period of performances to

values not less than 1/5 ft candle (2 lux).

According to NFPA 101, for the purposes of Illumination of means of egress, exit access shall

include only designated stairs, aisles, corridors, ramps, escalators, and passageways leading to an

exit. For the purposes of this requirement, exit discharge shall include only designated stairs,

aisles, corridors, ramps, escalators, walkways, and exit passageways leading to a public way.

Illumination of means of egress shall be continuous during the time that the conditions of

occupancy require that the means of egress be available for use. Artificial lighting shall be

employed at such locations and for such periods of time as are necessary to maintain the

illumination to the minimum criteria values herein specified. Automatic, motion sensortype

lighting switches shall be permitted within the means of egress, provided that the switchcontrollers are equipped for fail-safe operation, the illumination timers are set for a minimum 15-

minute duration, and the motion sensor is activated by any occupant movement in the area served

by the lighting units.


26/28

2.13.1 SourceIllumination of means of egress shall be from a source considered reliable by the authority

having jurisdiction. Battery-operated electric lights and other types of portable lamps or lanterns

shall not be used for primary illumination of means of egress. Battery-operated electric lights

shall be permitted to be used as an emergency source to the extent permitted.

2.13.2 Alternate source2.13.3 Illumination level

The floors and other walking surfaces within an exit and within the portions of the exit access

and exit discharge designated in 7.8.1.1 shall be illuminated as follows:

(1) During conditions of stair use, the minimum illumination for new stairs shall be at least 10 ft-

candle (108 lux), measured at the walking surfaces.

(2) The minimum illumination for floors and walking surfaces, other than new stairs during

conditions of stair use, shall be to values of at least 1 ft-candle (10.8 lux), measured at the floor.

(3) In assembly occupancies, the illumination of the walking surfaces of exit access shall be at

least 0.2 ft-candle (2.2 lux) during periods of performances or projections involving directed

light.

(4)*The minimum illumination requirements shall not apply where operations or processes

require low lighting levels.

Required illumination shall be arranged so that the failure of any single lighting unit does not

result in an illumination level of less than 0.2 ft-candle (2.2 lux) in any designated area.

The equipment or units installed to meet the requirements of Section 7.10 also shall be permitted

to serve the function of illumination of means of egress, provided that all requirements of Section

7.8 for such illumination are met.

2.13.4 Illumination intensity2.14 Refuge area

2.14.1 RequirementFor buildings more than 24m in height, refuge area of 15m2 or an area equivalent to 0.3m2 per

person to accommodate the occupants of two consecutive floors, whichever is higher, shall be

provided as under.

The refuge area shall be provided on the periphery of the floor or preferably on a cantilever

projection and open to air at least on one side protected with suitable railings.


27/28

a) For floors above 24m and up to 39m, one refuge area on the floor immediately above 24 m.

b) For floors above 39m, one refuge area on the floor immediately above 39m and so on after

every 15m. Refuge area provided in excess of the requirements shall be counted towards FAR.

2.14.2Location

2.14.3 Access2.14.4 Connectivity2.14.5 Protection2.14.6 Illumination

2.14.7Marking

2.15 Horizontal exitAccording to NFPA 101, Horizontal exit is a way of passage from one building to an area of

refuge in another building on approximately the same level, or a way of passage through or

around a fire barrier to an area of refuge on approximately the same level in the same building

that affords safety from fire and smoke originating from the area of incidence and areas

communicating therewith. Horizontal exits shall be permitted to be substituted for other exits

where the total egress capacity and the total number of the other exits (stairs, ramps, dooropenings leading outside the building) is not less than half that required for the entire area of the

building or connected buildings, and provided that none of the other exits is a horizontal exit,

unless otherwise permitted.

The width of horizontal exit shall be same as for the exit door ways. A horizontal exit shall be

equipped with at-least one fire/ smoke door of minimum one hour fire resistance of self closing

type. Further, it is required to have direct connectivity to the fire escape staircase for evacuation.

For buildings more than 24m in height, refuge area of 15m2 or an area equivalent to 0.3m2 per

person to accommodate the occupants of two consecutive floors, whichever is higher, shall be

provided. Where there is a difference in level between connected areas for horizontal exits,

ramps, not more than 1 in 10 m slope shall be provided; steps shall not be used. Doors in

horizontal exits shall be operable at all times from both sides.


28/28

2.15.1 Requirement2.15.2 Minimum width2.15.3 Access2.15.4 Protection2.15.5 Marking2.15.6 Illumination

2.16 Exit door hardware2.17 Fire Check Door2.18 Means of egress: Underground Structures

INSERT

fire - egress

Documents