Appendix B — Division B

Fire Safety in High Buildings

B-3.2.6. Smoke Control for High Buildings
Experience with high buildings has shown that the time required for complete evacuation can exceed that which is considered necessary for the safe egress of all occupants. Studies of the “chimney effect” and observations of smoke movement in actual fires have shown that fire compartmentation to contain a fire on any one storey will not usually prevent the movement of smoke through elevator, stair and other vertical shafts to the upper floors of a high building. Occupants of a high building in which an automatic sprinkler system is not installed, and particularly those on upper storeys, could be faced with severe smoke conditions from fires occurring in storeys below them before their own evacuation is possible. The requirements of Subsection 3.2.6. are intended to maintain safe conditions for occupants of a high building who may have to remain in the building during a fire, and to assist the firefighters by providing efficient access to the fire floor. The material in this Appendix is intended to assist a designer in complying with the requirements of Subsection 3.2.6. The knowledge requirements are well within the capabilities of a competent designer. The designer should appreciate, however, that successful application requires a clear understanding of the principles that govern smoke movement. Subsection 3.2.6. contains only those items that relate to the design and construction of a building; operation of the facilities and recommended actions to be taken by the building owner, occupant and fire department are covered by the British Columbia Fire Code.
The designer is cautioned that the tabular and graphical information in this Appendix has been developed for buildings having conventional configurations. The designer has to judge the extent to which the building under consideration has characteristics that will allow the application of this information; this is particularly true of designs employing air-handling systems for which a realistic assessment of the leakage characteristics of the enclosures of spaces may be critical.
It is assumed that buildings regulated by Subsection 3.2.6. will be in an area served by a fire department capable of an early response and that all firefighting and rescue situations will be under the direct control of the officer-in-charge of the fire department responding to the emergency. It is important that firefighters be provided with a smoke-free access to fire floors below grade. Provisions are included to separate exit stairways serving storeys above grade from those serving storeys below grade, and to limit entry of smoke into these shafts. Similarly, elevator hoistways and service shafts are required to be provided with a separation near grade, or be designed to limit their functioning as paths of smoke movement into upper floor areas from storeys below grade.
It is assumed that in the event of fire, occupants of the floor on which the fire occurs will leave by exit stairs immediately following the sounding of a fire alarm, and that occupants of the floor immediately above the floor on which the fire occurs will be advised to leave by the first fire department officer on the scene or other person assigned this responsibility. Occupants of all other floors may remain on their floors unless otherwise directed. It is also assumed that the owner of the building has complied with the Emergency Planning Section of the British Columbia Fire Code by preparing a comprehensive fire safety plan to safeguard the building occupants and that the building supervisory staff are familiar with the requirements of Subsection 3.2.6. and with their responsibilities under the fire safety plan.
The British Columbia Building Code requires that a check be made of the smoke control and mechanical venting systems. Testing will indicate deficiencies caused by inexact estimates of the leakage characteristics or of air supply requirements and, in all but the most extreme cases, will provide an opportunity for appropriate adjustments before the system is put into service.

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B-3.2.6.2.(2) Stairway Protection Below Lowest Exit Level
A stairway serving floors below the lowest exit level is considered to comply with the intent of Sentence 3.2.6.2.(2) if the following conditions are satisfied.
1) The stairway has a vent or door to the outdoors at or near the top of the stairshaft that has an openable area of not less than 0.1 m2 for each storey served by the stairway, less 0.01 m2 for each weatherstripped door and 0.02 m2 for each door that is not weatherstripped opening into the stairway.
2) The stairway is enclosed in a shaft that
  1. does not pass through the floor above the lowest exit level and is separate from a shaft that contains a stairway serving upper storeys, or
  2. contains a stairway serving upper storeys, but is separated from that stairway at the lowest exit level by a fire separation having a fire-resistance rating not less than that required for the shaft enclosure.
3) The stairway is provided with equipment capable of maintaining a flow of air introduced at or near the bottom of the stair shaft, at a rate equal to 0.47 m3/s for each storey served by the stairway.
B-3.2.6.2.(3) Pressurization of Stair Shafts
The purpose of providing open doors and vents at the bottom of a stair shaft is to create a positive pressure in the shaft relative to adjacent floor areas and thus keep it free of smoke. The pressure depends on the temperature differential between the interior and the exterior of the building which is most pronounced during winter months when stack effect is greatest. If a shaft does not have a direct opening to the exterior, alternative means must be provided to achieve smoke control. If a corridor or vestibule is used as a link between the exit level of an interior stair shaft and the outdoors to provide a venting system, it will be necessary to assess the reliability of the overall system. The probability of all doors or closures being opened at the same time has to be addressed, as well as the size of the vestibule and its impact on the overall smoke control system.
If mechanical methods are used to develop a positive pressure in a stair shaft, a minimum pressure differential of 12 Pa is recommended to prevent smoke migration from floor areas in a sprinklered building where fire temperatures are controlled and smoke movement may be dominated by stack effect in a stair shaft. During a fire emergency, persons will be entering and exiting a stair shaft as they move to a place of safety and under these conditions the number of doors open to the stair shaft cannot be predetermined. The number will vary depending on the occupancy of the building, population density and the evacuation plan for the building. It should be assumed that two doors are open. This is based in part as a practical level for most buildings and considers the positive fire experience in sprinklered buildings.
The maximum pressure differential created by a mechanical system should not prevent doors to the stair shafts from being opened. A specific maximum value cannot be given, as this value will depend on the door opening force and size of the door. These values should be calculated for each specific case. Although a maximum value of 130 N is suggested by research as the force that can be opened by the majority of people in most occupancies, this value is above the maximum value of 90 N generally specified in this Code. The use of values below 130 N can create a practical problem in achieving effective smoke control as it is difficult to design for the acceptable minimum and maximum pressure differential range. Special consideration may need to be given for doors located in an accessible path of travel.
Care should be taken by designers and by building and fire officials in implementation of these requirements. Assumptions involved in the design of a smoke control system may be different from final construction conditions. For this reason each system should be tested after installation to ensure that the design intent is met. The minimum pressure differential is not intended to apply to locations in stair shafts when doors in their proximity are open to adjacent floor areas.
B-3.2.6.2.(4) Limiting Smoke Movement
Measures to prevent the migration of smoke from floor areas below the lowest exit storey into upper storeys include the following.
1) An elevator hoistway that passes through the floor above the lowest exit storey should not penetrate the floor of the storey immediately below the lowest exit storey, unless there is a vestibule between the shaft and each floor area below the lowest exit storey that
  1. has a fire separation, with a fire-resistance rating not less than 45 min, between the vestibule and any public corridor,
  2. has a fire separation, with a fire-resistance rating not less than that required for an exit by Article 3.4.4.1., between the vestibule and any stair or elevator enclosure or any part of a floor area, other than a public corridor, and
  3. except for elevator hoistway entrances, has a self-closing device on any door through the fire separation required by Clauses (a) and (b), with the door opening in the direction of travel from the floor area to the exit stairway.
Figure B-3.2.6.2.(4)-A
Vent to a vertical service space with no other pressurized shaft in the building
Notes to Figure B-3.2.6.2.(4)-A:
(1)
Curve A applies to a vertical service space that is enclosed by unplastered unit masonry or by plaster and steel stud construction with all openings in the shaft sealed to the degree required by Articles 3.1.9.1. to 3.1.9.4.
(2)
Curve B applies to a vertical service space that is enclosed by monolithic concrete or by plastered unit masonry with all openings in the shaft sealed tightly to minimize air leakage.
(3)
A shaft having a vent that is 100% of the cross-sectional area of the shaft is acceptable for buildings up to 1.5 times the height shown by the appropriate curve in Figures B-3.2.6.2.(4)-A and B-3.2.6.2.(4)-B.
(4)
The total leakage area, based on measurements in typical high buildings, is assumed to be 0.025 m2 for every 10 m2 of shaft wall area in the case of Curve A and 0.015 m2 for every 10 m2 of shaft wall area in the case of Curve B.
2) A vertical service space, other than an elevator hoistway, that passes through the floor assembly above the lowest exit storey, should be provided with a tight-fitting noncombustible seal or fire stop at the floor assembly of the storey immediately below the lowest exit storey, unless
  1. the vertical service space is vented to the outdoors at the top and the vent has an openable area that is not less than
    1. that obtained from Figure B-3.2.6.2.(4)-A if the vertical service space is in a building in which other shafts are not mechanically pressurized, or
    2. that obtained from Figure B-3.2.6.2.(4)-B if the vertical service space is in a building in which other shafts are mechanically pressurized,
  2. for a shaft that serves floor areas above the lowest exit storey, a vent is located
    1. at or near the top of the shaft if the shaft is above the mid-height of the building, or
    2. at or near the foot of the shaft at or near the exit level if the top of the shaft is below the mid-height of the building, or
  3. for a shaft that serves floor areas below the lowest exit storey, a vent is located at or near the top of the shaft.
3) Any closure provided for a vent opening referred to in Sentence (2) must be openable:
  1. manually,
  2. on a signal from a smoke detector located at or near the top of the shaft, and
  3. by a control device located at the central alarm and control facility.
Figure B-3.2.6.2.(4)-B
Vent to a vertical service space with other pressurized shafts in the building
Notes to Figure B-3.2.6.2.(4)-B:
(1)
Curve A applies to a vertical service space that is enclosed by unplastered unit masonry or by plaster and steel stud construction with all openings in the shaft sealed to the degree required by Articles 3.1.9.1. to 3.1.9.4.
(2)
Curve B applies to a vertical service space that is enclosed by monolithic concrete or by plastered unit masonry with all openings in the shaft sealed tightly to minimize air leakage.
(3)
A shaft having a vent that is 100% of the cross-sectional area of the shaft is acceptable for buildings up to 1.5 times the height shown by the appropriate curve in Figures B-3.2.6.2.(4)-A and B-3.2.6.2.(4)-B.
(4)
The total leakage area, based on measurements in typical high buildings, is assumed to be 0.025 m2 for every 10 m2 of shaft wall area in the case of Curve A and 0.015 m2 for every 10 m2 of shaft wall area in the case of Curve B.
B-3.2.6.3.(1) Connected Buildings
The measures described here are intended to prevent movement of smoke from one building to another. They are of particular significance for two buildings of unequal height that are joined together. The techniques suggested are the provision of a large opening to the outdoors in a connecting vestibule so that smoke entering through leakage areas around doors will be vented to the outdoors, or pressurization to maintain a higher pressure in the vestibule than in adjacent spaces, as illustrated in Figures B-3.2.6.3.(1)-A, B-3.2.6.3.(1)-B and B-3.2.6.3.(1)-C.
The provisions for protection of openings are described in terms appropriate to a doorway. Openings other than doorways should be avoided if possible. Openings should be protected by an airlock that gives the same standard of protection as the vestibule referred to below.
The requirement of Article 3.2.6.3. that limits movement of smoke from one building to another may be met by incorporating in the link between the buildings the provisions of Sentences (1) and (2).
1) A firewall conforming to Subsection 3.1.10. is constructed between one building and the other with any opening in the firewall protected against the passage of smoke by a vestibule that has
  1. a fire separation between the vestibule and a public corridor with a fire-resistance rating not less than 45 min,
  2. a fire separation between the vestibule and the remainder of the floor area, other than a public corridor, with a fire-resistance rating not less than that required by Article 3.4.4.1. for an exit,
  3. a fire separation between the vestibule and a stair enclosure or elevator hoistway with a fire-resistance rating not less than that required by Article 3.4.4.1. for an exit, and
  4. any door in the fire separation required by Clauses (a), (b) or (c), except for an elevator entrance, provided with a self-closing device as required by Article 3.1.8.11. and opening in the direction of travel from the floor area to the exit stairway.
2) The vestibule referred to in Sentence (1) should have
  1. a vent to the outdoors that has a net area of 10(0.023 d + 0.00045 a) m2, where 'd' is the number of doors having a perimeter not more than 6 m that open into the vestibule, or if the perimeter of doors exceeds 6 m, the value 'd' is increased in direct proportion to the increase in the perimeter, and 'a' is the area in square metres of enclosing walls, floors and ceilings whose outer face is in contact with the outside air, except that where the outer face of a wall is in contact with the ground or fill, it is assumed that there is no leakage through that portion, and the value of 'a' is assumed to be zero, or
  2. equipment capable of maintaining a supply of air into the vestibule sufficient to ensure that the air pressure in the vestibule when the doors are closed is higher by at least 12 Pa than that in adjacent floor areas when the outdoor temperature is equal to the January design temperature on a 2.5% basis.
Figure B-3.2.6.3.(1)-A
Buildings connected by a tunnel
Figure B-3.2.6.3.(1)-B
Buildings connected at a firewall
Figure B-3.2.6.3.(1)-C
Buildings connected by a bridge
B-3.2.6.5.(6)(b) Electrical Cable Protection
Electrical cables that provide continuous operation for 1 h when subjected to the fire exposure of the time/temperature curve of CAN/ULC-S101, “Fire Endurance Tests of Building Construction and Materials,” do not need additional protection against exposure to fire.
B-3.2.6.6.(1) Venting to Aid Firefighting
The requirements of Sentence 3.2.6.6.(1) are met by incorporating in a floor area windows or wall panels, as described in Sentence (1), by smoke shafts as described in Sentences (2) to (8), or by the use of building exhaust systems as described in Sentence (9).
1) If windows or wall panels are used for venting, they must
  1. be uniformly distributed along the exterior wall of each storey,
  2. have a total area not less than 1% of the exterior wall area of each storey,
  3. be readily openable from the interior without the use of wrenches or keys,
  4. be readily identified from the interior, and from the exterior where they are accessible to firefighters, and
  5. be designed so that when opened they will not endanger persons outside the building during a fire.
2) If one or more smoke shafts or vertical service spaces are used for venting, they must
  1. have an opening or openings into each storey with an aggregate area not less than that obtained from Table B-3.2.6.6.(1)A for the height of the building and the area of the largest floor area served by the smoke shaft, and the leakage characteristics of the shaft wall and closures obtained from Table B-3.2.6.6.(1)B, and Table B-3.2.6.6.(1)C,
  2. have an aggregate unobstructed cross-sectional area equal to that required by Clause (a), and
  3. be designed to comply with the requirements of Sentence (3).
3) Each smoke shaft or vertical service space described in Sentence (2) must
  1. be separated from the remainder of the building by a fire separation that has a fire-resistance rating not less than that required for the floor assembly through which it passes, or be designed as a chimney conforming to Part 6, except that flue liners need not be provided,
  2. have an opening to the outdoors at the top that has an area not less than the cross-sectional area of the shaft, with the opening protected from the weather,
  3. terminate not less than 900 mm above the roof surface where it penetrates the roof, and
  4. contain no combustible material, fuel lines or services that are required for use in an emergency.
4) Each opening required by Clause (2)(a) must be located so that the top of the opening is not more than 250 mm below the ceiling, except that the opening may be above the ceiling if the ceiling freely allows passage of air.
5) The opening into the smoke shaft must be provided with a closure that
  1. has a fire-protection rating conforming to Sentence 3.1.8.4.(2), except that the temperature on the unexposed face of the closure shall be not more than 250 °C after 30 min during the fire test used to determine its rating,
  2. is no closer to combustible material, except for paint or tightly-adhering paper covering not more than 1 mm thick applied to a noncombustible backing, than the distances described in Table B-3.2.6.6.(1)D,
  3. can be opened from a remote location such as a stair shaft, the storey immediately below, or the central alarm and control facility, and
  4. does not open automatically on any floor, other than the fire floor, when smoke and hot gases pass through the shaft.
6) Closures for openings described in Clause (3)(b) must
  1. be openable from outside the shaft, and
  2. open automatically
    1. on a signal from a smoke detector in the shaft,
    2. by operation of the fire alarm system, and
    3. when the closure required by Sentence (5) opens.
7) A smoke shaft opening referred to in Sentence (2) that is less than 1 070 mm above the floor must conform to Article 3.3.1.18.
8) If a closure is required to comply with Sentence (5), the leakage area between closure components and between closure and frame must not be more than 3% of the openable area of the closure.
9) The building air handling system may be used for smoke venting, provided
  1. the system can maintain an exhaust to the outdoors at the rate of 6 air changes per hour from any floor area, and
  2. emergency power to the fans providing the exhaust required by Clause (a) is provided as described in Article 3.2.7.9.
Table B-3.2.6.6.(1)A
Minimum Size of Vent Openings into Smoke Shafts from Each Floor Area, m2(1)(2)
Forming part of Appendix Note B-3.2.6.6.(1)

Floor
Area,
m2

Leakage Area, %(3)

 Building Height, m
18 37 73 110 146 183 220 256 293
200 0 0.10 0.11 0.13 0.15 0.16 0.18 0.19 0.20 0.22
500 0.22 0.25 0.29 0.32 0.36 0.37 0.39 0.41 0.43
1 000 0.43 0.48 0.53 0.59 0.63 0.67 0.71 0.75 0.77
2 000 0.83 0.91 1.01 1.08 1.16 1.22 1.29 1.34 1.39
3 000 1.21 1.33 1.46 1.55 1.67 1.75 1.82 1.90 1.97
4 000 1.62 1.75 1.90 2.02 2.15 2.25 2.35 2.44 2.53
5 000 2.01 2.17 2.34 2.46 2.63 2.74 2.86 2.88 3.07
6 000 2.39 2.57 2.76 2.91 3.10 3.23 3.37 3.47 3.58
200 1 0.10 0.12 0.15 0.19 0.22 0.27 0.35 0.43 0.55
500 0.23 0.27 0.35 0.40 0.49 0.57 0.69 0.83 1.04
1 000 0.44 0.50 0.71 0.72 0.86 1.01 1.19 1.43 1.73
2 000 0.85 0.97 1.15 1.33 1.56 1.81 2.10 2.48 2.95
3 000 1.26 1.42 1.67 1.91 2.23 2.56 2.97 3.47 4.08
4 000 1.66 1.88 2.18 2.49 2.37 3.28 3.79 4.40 5.16
5 000 2.07 2.32 2.69 3.05 3.51 3.99 4.60 5.32 6.21
6 000 2.47 2.76 3.18 3.59 4.14 4.68 5.37 6.20 7.23
200 2 0.10 0.13 0.18 0.24 0.37 0.61 1.28 4.60 89.57
500 0.24 0.29 0.39 0.52 0.75 1.13 2.10 6.11 94.50
1 000 0.46 0.55 0.72 0.94 1.30 1.90 3.27 8.29 102.11
2 000 0.88 1.05 1.34 1.73 2.32 3.28 5.36 12.14 116.80
3 000 1.31 1.53 1.95 2.47 3.29 4.58 7.28 15.63 130.83
4 000 1.73 2.01 2.55 3.20 4.23 5.83 9.12 19.97 144.03
5 000 2.15 2.49 3.13 3.92 5.15 7.05 10.90 22.15 157.05
6 000 2.57 2.96 3.73 4.63 6.07 8.26 12.65 25.39 169.29
200 3 0.11 0.14 0.21 0.37 0.88 2.06      
500 0.25 0.31 0.47 0.76 1.58 9.00      
1 000 0.47 0.59 0.86 1.33 2.60 11.99      
2 000 0.91 1.12 1.60 2.41 4.47 17.46      
3 000 1.35 1.64 2.31 3.43 5.21 22.48      
4 000 1.79 2.17 3.02 4.43 7.91 27.29      
5 000 2.22 2.68 3.71 5.42 9.55 31.95      
6 000 2.65 3.20 4.40 6.39 11.18 36.47      
200 4 0.11 0.15 0.28 0.70 24.83        
500 0.25 0.34 0.58 1.33 29.18        
1 000 0.49 0.63 1.06 2.27 36.07        
2 000 0.95 1.21 1.97 3.99 48.56        
3 000 1.41 1.78 2.84 6.63 60.15        
4 000 1.86 2.34 3.70 7.22 71.15        
5 000 2.21 2.90 4.55 8.79 81.81        
6 000 2.75 3.46 5.40 10.33 90.05        
200 5 0.11 0.16 0.36 3.33          
500 0.28 0.36 0.76 5.09          
1 000 0.50 0.69 1.37 7.67          
2 000 0.99 1.31 2.54 12.35          
3 000 1.46 1.94 3.65 16.75          
4 000 1.92 2.55 4.75 20.99          
5 000 2.40 3.16 5.84 25.11          
6 000 2.87 3.74 6.92 29.11          
Notes to Table B-3.2.6.6.(1)A:
(1) The minimum size of a vent opening into a smoke shaft is obtained from Table B-3.2.6.6.(1)A and is dependant on the floor area and total leakage area of the smoke shaft walls and closures. This total leakage area may be estimated by adding the leakage areas for the shaft wall obtained from Table B-3.2.6.6.(1)B and for the dampered openings obtained from Table B-3.2.6.6.(1)C, provided the cross-sectional area of the smoke shaft, the opening into the shaft and the opening to the outdoors at the top of the shaft are equal.
(2) The size of the vent opening refers to the free or unobstructed area of the opening.
(3) Leakage area is the total of the leakage area of smoke shaft wall obtained from Table B-3.2.6.6.(1)B and the leakage area of openings in smoke shafts obtained from Table B-3.2.6.6.(1)C.
Table B-3.2.6.6.(1)B
Leakage Area of Smoke Shaft Wall
Forming part of Appendix Note B-3.2.6.6.(1)
Wall Construction Leakage Area as % of Wall Area
Monolithic concrete 0.5
Masonry wall unplastered 1.5
Masonry wall plastered 0.5
Gypsum board on steel studs 1.0
Table B-3.2.6.6.(1)C
Leakage Area of Closures in Openings into Smoke Shaft
Forming part of Appendix Note B-3.2.6.6.(1)
Type of Closure

Leakage Area as % of Closure Area(1)(2)
Curtain fire damper 2.5
Single-blade fire damper 3.5
Multi-blade fire damper 4.5
Notes to Table B-3.2.6.6.(1)C:
(1) Values include allowance for 0.5% leakage between frame and wall construction.
(2) These leakage data are based on clearances applicable to closures that have been tested in accordance with CAN/ULC-S112-M, “Fire Test of Fire-Damper Assemblies.”
Table B-3.2.6.6.(1)D
Minimum Distance from Closure to Combustible Material
Forming part of Appendix Note B-3.2.6.6.(1)

Area of Closure(1), m2

 Minimum Distance in Front of or Above Closure, m Minimum Distance to the Sides or Below Closure, m
0.5 0.35 0.20
1.0 0.50 0.25
1.5 0.60 0.30
2.0 0.70 0.35

2.5(2)

 0.80 0.40
Notes to Table B-3.2.6.6.(1)D:
(1) For closure areas between those given in Table B-3.2.6.6.(1)D, interpolation may be used to determine the appropriate distances.
(2) For closure areas greater than 2.5  m2, the minimum distance in front of or above the closure shall be one half of the square root of the closure area, and the minimum distance to the sides or below the closure shall be one quarter of the square root of the closure area.
B-3.2.6.7.(1) Protection of Central Control Room
The design of a room provided for a central alarm and control facility should take into account the nature and sensitivity of the electronic components of the equipment and the room should be adequately protected from fire and smoke. The room should be ventilated with a supply of fresh air so that it has a clean environment and should be provided with adequate lighting.
B-3.2.6.7.(2) Central Control Room Air Control
Depending on the method of mechanical venting and air control that is selected for the building, additional controls may be required at the central alarm and control facility. These additional controls include those with a capability of opening closures to vents in shafts, stopping air-handling systems, and initiating mechanical air supply to stair shafts.
B-3.2.6.9.(1) Testing for Smoke Control
The efficiency of a smoke control system may be checked by measuring pressure differences and the directions of airflow around doors and through separating walls of compartments. A pressure meter can be used to measure pressure differences on either side of a door or partition. Where this is impracticable, a punk stick held near a crack will indicate the direction of airflow. Measurements of airflow may be taken on the intake side of supply fans or in supply ducts to determine whether the specified airflow is being provided. In general, airflow should be from the spaces which may be occupied for various lengths of time during a fire emergency (e.g., vestibules, stair shafts, and elevator hoistways) toward the space in which the fire is assumed to have occurred. Measurements may be taken at certain critical locations to check the overall efficiency of the smoke control system.
In buildings where protection is obtained by venting corridors or vestibules to the outdoors, inspection of the building to determine whether the requirements have been met should be sufficient. Where service shafts are vented to the outdoors at the top, a check may be made of the wall between the shaft and the uppermost occupied floor areas, to ensure that the direction of flow is from each floor area into the shaft, when the vent to the outside is open and the outdoor air temperature is significantly less than that indoors. Where mechanically pressurized vestibules are used, a check may be made to ensure that the pressure in each vestibule or area of refuge is greater than that in the adjacent floor areas at each floor level.
Doors to stair shafts, elevator hoistways and vestibules in locations subject to pressure differences that may interfere with normal opening should be checked when the outdoor temperature is near the January design temperature, with the air injection system operating and a number of windows open to the outdoors on each floor in turn.
This Appendix is included for explanatory purposes only and does not form part of the requirements. The numbers that introduce each Appendix Note correspond to the applicable requirements in this Division.