Means of Egress
There are three distinct definitions
concerning the topic of egress and these are defined in OBC 1.1.3.2.(1). As a
general rule, the intent of the building code is to ensure that a minimum
standard is maintained with regards to the ability of any occupant to exit the
building safely from anywhere in the building at any time. That is the
objective. Providing for this objective to be met properly can be a complicated
and often time consuming activity – both in design and construction. Consider
the three main definitions for egress:
- Exit
- Access to Exit
- Means of Egress
A diagram to describe these three
conditions for a typical 2 or 3 storey building requiring 2 exits shows the hierarchical
order in which means of egress are considered. As a rule, means of egress is
from ‘anywhere in the building’. An access to an exit is a protected path where
the potential ‘crush’ or large and immediate congregation of persons might occur.
(I.e. a corridor). A corridor is not the only kind of access to exit but it is
the most common.
Figure 1 Diagram
showing egress conditions
An exit from any floor area shall be one of
the following used singly or in combination:
- an exterior doorway
- an exterior passageway
- an exterior ramp
- an exterior stairway
- a fire escape
- a horizontal exit
- an interior passageway
- an interior ramp, or
- an interior stairway
Access to Exits
As a general rule, each suite in a floor
area occupied by more than one suite shall have
- an exterior exit doorway, or
- a doorway to a public corridor or
to an exterior passageway
Where the doorway enters a public corridor
or exterior passageway it shall be possible to go in two directions to reach an
exit. The exception to this rule is indicated in article 9.9.7.2. Dead End
Corridors. This article provides for the maximum conditions for dead end
corridor lengths based on the occupancy served
Figure 2 Exit Diagram
Measurement of Travel Distance (9.9.8.1)
Subsection 9.9.8. defines travel distance
as the distance from any point in the floor area to an exit measured along the
path of exit travel. The following is a summary of maximum travel distances
permitted in Sentence 9.9.8.2.1.(1).
Occupancy Not
Sprinklered Sprinklered
Business and Personal Service 40m
(131 ft.) 45m (148 ft.)
Other Occupancies 30m
(98 ft.) 45m (148ft.)
The point at which this measurement for
travel distance may be taken is further described in Sentence 9.9.8.1.(2) –
where a room or suite is separated from the remainder of the floor area by a fire
separation having a fire-resistance rating of at least 45 min, or in
a sprinklered building, by a fire separation which is not required to
have a fire-resistance rating, the travel distance is permitted to be
measured from an egress door of the room or suite to the nearest exit
Number of Required Exits (9.9.8.2.)
A single exit from a storey is permitted
where:
Building does not exceed two storeys and
conforms to floor area, travel distance and occupant load calculations
described in 9.9.7.3.
Questions
1.
Describe the conditions where a single exit is
permitted from a Part 9 building
OBC Reference:
2.
As a general rule, how is Travel distance
measured?
OBC Reference:
3.
What conditions need to be satisfied in order to
avoid measuring the travel distance from the most remote point in a building to
an exit?
OBC Reference:
Flame Spread Ratings
Flame Spread Rating is defined as an index
or classification indicating the extent of spread of flame on the surface of a
material or an assembly of materials as determined in accordance with articles
9.10.3.2. and 3.1.12.1. When reading these articles it should be understood
that the general rule and intent is to limit flame spread in areas and pathways
that would lead occupants to a safe egress from a building. The following is a
list of requirements from Part 9 related to flame spread ratings (FSR)
OBC Reference Description
9.10.3.2.(1) Testing
9.10.3.2.(2) Cut surfaces
9.10.15.1 Compartmentation of
concealed spaces
9.10.16.1 Interior finishes,
general rule
9.10.16.2. Ceilings in exits
or public corridors
9.10.16.3. Walls in exits
9.10.16.4 Exterior exit
passageways
9.10.16.5 Walls in public
corridors
9.10.16.7 Interior finishes
for occupancies in public corridors or corridors used by the public
9.10.16.8 Light diffusers and
lenses
9.10.16.10 Foamed plastic wall
or ceiling finish in combustible construction
Flame Spread Rating of Interior Surfaces
As a general rule the exposed surface of
every interior wall and ceiling, including skylights shall have a surface flame
spread rating of not more than 150. Doors within dwelling units do not need an
assigned Flame Spread Rating. Other doors require FSR of 200.
Flame Spread Rating for Ceilings in Exits
At least 90% of the exposed surface of
every ceiling in a public corridor shall have a surface flame spread
rating of not more than 25. OBC 9.10.16.6. excludes certain items from the
calculation of ceiling area. These are skylights, glazing, combustible doors,
and combustible light diffusers and lenses shall not be considered in the
calculation of wall and ceiling areas
Flame Spread Rating for Walls in Exits
90% of the exposed surfaces of every wall
in an exit shall have a surface flame spread rating of not more than 25. For
lobbies this percentage is reduced to 75% of the wall area with an FSR of 25
(OBC 9.10.16.3.(2)
Flame Spread Rating for Walls in Corridors
90% of the total wall surface in any
unsprinklered public corridor shall have a surface flame spread rating of not
more than 75 or at least 90% of the upper half of such walls shall have a
surface flame spread rating of not more than 25.
Flame Spread Rating Chart
Area FSR
Interior Surfaces 150
Doors 200
Ceilings in Exits 25
(over 90% of the area)*
Walls in Exits 25
(over 90% of the area)*
Walls in Lobbies used as Exits 25
(over 75% of the area)*
Walls in Public Corridors 75
(over 90% of the area) OR
Walls in Public Corridors 25
(over 90% of the upper half of the walls)*
Walls and Ceilings in Bathrooms 200
Doors within dwelling units Unassigned
* Note: Skylights, glazing, combustible
doors, and combustible light diffusers and lenses shall not be considered in
the calculation of wall and ceiling areas
When reading into the requirements for
Flame Spread Ratings be sure to verify that the term ‘surface flame spread is
used. For instance, if the reference is to the required Flame Spread Rating
only and not the ‘surface’ Flame Spread Rating then the Requirements also apply
to the material if it were cut through.
9.10.3.2. Flame Spread Rating
This article makes a reference to Part 3
and the Supplementary Guidelines. The article states that where a flame spread
rating is required it shall be determined in accordance with the test methods
in Part 3 or the Supplementary Guidelines. Read 3.1.12.1 to find 2choices in
determining the FSR of various materials
- Determined on the basis of not less than
three tests conducted in conformance with CAN/ULC-S102.2)-M, “Standard
Method of Test for Surface Burning Characteristics of Building Materials
and Assemblies”. The same standard is also in place for floors but bear in
mind that floors are not assigned a required FSR until the building is
considered ‘high’ according to 3.2.6. So unless the building is a ‘high
building’ floors need not be given a FSR
- The second allowable method is to
determine the FSR using the Supplementary Guidelines (SG-2). This method
is easier.
Smoke Development Classification
Another important consideration to be made
with FSR is the Smoke Development classification. This is an index on the
general tendency of a material to propagate smoke under heated or flame
conditions. Part 9 does not explicitly refer to the Smoke Development
Classification of interior finishes. These are identified however in SG-2 along
side the Flame spread ratings for various materials