Fire Protection & Design Supplement: Is Smoke Control Really Required?
High-rise office buildings--buildings over 75 feet in height--have required life safety designs for many years. The previous life safety provisions required stairwell pressurization and smoke evacuation (either mechanical or through knockout windows). The Uniform Building Code added Section 905, Smoke Control, to the code in the 1991 edition. It has been implemented in many buildings during the years it has been in force.
Does complying with Section 905 of the UBC provide additional protection over and above the protection provided by the previous smoke control requirements? This is the main issue of this article. It should be noted that this article only relates to fully sprinklered high-rise office buildings greater than 75 feet in height.
For clarification, "smoke control" shall relate only to the requirements of Section 905 of the UBC which are over and above those required by the 1988 UBC. This includes the rational analysis, additional control features, monitoring of the damper positions and yearly testing of these systems. The base comparison is a high-rise office building with stairwell pressurization and a smoke evacuation system (either mechanical or knockout windows). The information presented herein indicates that smoke control would not have been beneficial to the occupants of the high-rise office buildings during the emergency (this statement does not include the stairway pressurization system).
The following information discusses data obtained from two documents purchased from the National Fire Protection Association (NFPA). The documents are:
The purpose in presenting this information is to provide data supporting the contention that fire alarm systems and fire sprinklers in high-rise office buildings provide the true life/safety functions required to protect the occupants' health and safety. The data also shows that the dangers associated with smoke in past experiences would not have been greatly reduced with a smoke control system in place. And, the data will support the contention that if fire sprinklers had been installed, the dangers would have been greatly reduced, and as such, a smoke control system would not have provided substantial additional benefit.
"High-Rise Building Fires" Report DataThis report includes fire statistics for high-rise buildings collected over five years from 1993 to 1997. In 1997, only 10.3% of the fires reported were located in high-rise office buildings. The total direct property loss of all office buildings in 1997 is listed at $ 3,500,000. Yet, with only this small amount of property loss and no life loss, the code requires a sophisticated smoke control system that costs the owner approximately $1 per square foot.
While the majority of fires and associated losses occurred in high-rise apartment buildings, Table 1 indicates that only 10.3% of the fires took place in high-rise office buildings.
As indicated in Table 2, information provided during the period of 1993 to 1997 indicated that in buildings 7-12 stories in height, there were 320 fires, with a total property loss of $6 million. (The cost of smoke control for a project of this size is estimated at $500,000.) It should be noted, however, that no deaths occurred in office buildings greater than three stories during the five-year period.
NFPA's current (2000 edition) Life Safety Code, similar to previous editions, has provisions for existing as well as new high-rise buildings for each of the four property classes. (This supports the mandatory installation of fire sprinklers in all buildings, including existing buildings.) Fire sprinklers account for a 90% reduction in the rate of deaths per 1,000 fires (for the other three property classes, office buildings had zero deaths) and at least a 42% reduction in the average dollar loss per fire for each of the four property classes. Other systems installed provided the following statistics:
- Smoke alarms--61% reduction in the rate.
- Fire resistive construction--32% reduction in the rate.
It should be noted that smoke control did not provide any reduction in the rate of property loss during the five-year span studied.
The following evidence shows the value of using all these systems (fire protection systems, sprinklers, alarms, smoke detection, etc.) in high-rise buildings, as they keep the fire and smoke confined to the room, or at least the floor of fire origin.
Of the total 610 fires:
- In 570, fire and smoke were confined to room of origin.
- In 20, fire and smoke were confined to floor of origin.
- In 20, fire and smoke reached beyond floor of origin.
The report also provides a summary of research concerning smoke damage in high-rise office buildings. The research indicates that of the total of 610 fires, the breakdown of smoke damage was as follows:
- In 80, there was no smoke damage.
- In 310, smoke damage was confined to room of origin.
- In 100, smoke damage was confined to floor of origin.
- In 120, smoke damage reached beyond floor of origin (less than 20%).
In summary, the report offers the following statement:
"In any particular occupancy, high-rise buildings that have fires are much more likely to have sprinklers, detection/alarm systems, and the compartmentalization features associated with fire-resistive construction than lower-height buildings (of the same occupancy) that have fires. However, considering the extensive requirements in the Life Safety Code for fire and life safety features in both new and existing high-rise buildings, it seems clear that there are still major gaps, particularly in adoption and enforcement of the provisions requiring retrofit of automatic sprinkler systems and other life safety systems in existing high-rise buildings."
"High-Rise Fatal Fires--Office Buildings" Report DataTo determine the need for smoke control, your first step is to review historical data on past fires that provides the cause of the fires and the extent of the damage. This information can also indicate whether a smoke control system will have a positive effect in a fire. Reviews such as these are contained in this report from NFPA.
Rockefeller Plaza Fire (11 Stories)
The review of this fire and the facts surrounding it provided a list of the reasons the fire started and the damage that was caused. The research summarized its findings by listing eight significant contributing factors (none of which included smoke control):
- 1. Inadequate circuit protection
2. Lack of adequate space of electrical conductors
3. Unprotected vertical and horizontal penetrations
4. Lack of fire sprinklers
5. Lack of smoke detection
6. Confusing building layout
7. Failure of building fire alarm system
8. Multiple points of origin
Based on this information, smoke control would not have provided any additional protection in the fire. Therefore, the smoke control system would have been a waste of money and may have provided a false sense of security for the occupants.
World Trade Center (Seven Buildings)--First Event (Not 9/11)
This tragic event is probably the most well-known of recent fires due to the nature of its origin. Terrorist action caused the explosion and the corresponding smoke.
The buildings were surveyed for their operation during the emergency. Upon completion of the survey, the conclusions provided in the study were as follows:
- --Six deaths due to explosion, zero deaths due to smoke.
--Smoke in stairwells, due to the explosion damaging the lower floors' entrance into the stairwells.
--Emergency power turned off by fire department (so smoke control system would not have operated).
--Smoke movement could not have been prevented due to the explosion.
--"15 minutes after the explosion occurred, the smoke-filled stairways were plunged into darkness when the remaining normal and emergency electrical power supply was shut down, adding to the difficulty and confusion of the situation."
--"However, none of the deaths at the complex were attributed to the effects of smoke, despite the occupants' prolonged exposure and the lengthy evacuation."
--"Systems are widely considered to have been state-of-the-art for the period in which the complex was built. However, the violent explosion negated the potential protection that many of the existing systems provided."(These statements are quoted from the text of the report.)
The stairwells filled with smoke due to the explosions. Smoke had not migrated to the floors where floor smoke control systems (if installed) may have provided some degree of protection. Therefore, the rated doors into the stairwells provided the only protection needed by preventing the smoke from migrating to the floors.
Peachtree Fire, Atlanta, Georgia
A synopsis of the survey performed after the fire provided the following observations:
- --Smoke spread through corridor from the electrical room.
--Smoke spread from ceiling falling in due to fire, no sprinklers.
--"First, smoke from the fire in the room of origin quickly began to fill the corridor and advanced ahead of the flame front. The smoke entered the office spaces through doors that were left open, through cracks and openings around closed doors."
--"Second, the ceiling collapsed outside the room of fire origin."
Summary of Fire SurveysOther noteworthy fires included in the report were the Montreal High-Rise Fire, The Minneapolis Bank Building, Los Angeles County Health Building, One Meridian Plaza, and the First Interstate Bank Building in Los Angeles, California.
In each of the fires in this report, the majority of the damage was caused by the lack of fire sprinkler systems. In the case of the First Interstate Bank Building in Los Angeles, fire sprinklers were being installed but had not yet been activated at the time of the fire.
Smoke control systems would not have provided substantial additional benefits to the occupants during the fire. If a smoke control system would not have provided substantial additional benefit, then why require the installation of the systems in the newer high-rise office buildings?
Fire Sprinkler EffectivenessIn March 1981, the Fire Journal published a study performed by the City of New York. This study concerned the effectiveness of fire sprinklers in high-rise buildings. The study encompassed a period of just over three years. During this period, there were 115 high-rise fires, of which 41 buildings had fire sprinklers. Of the 41 fires, they were extinguished as follows:
- 34 fires with one sprinkler head
- 5 fires with two sprinkler heads
- 1 fire with three sprinkler heads
- 1 fire with four sprinkler heads
- No fires required more than four sprinkler heads
Based on the results of this study, no fire in a high-rise office building occurring through natural causes would contain a fire large enough to require the operation of a smoke control system for the safety of the occupants.
Smoke Control DiscussionSeveral lively discussions have taken place between those who are in full support of the current Section 905 of the UBC. However, it is interesting to note that the examples provided include buildings that were built prior to any smoke control requirements (i.e. stairwell pressurization, etc.) and did not include the installation of fire sprinklers.
The losses due to fire in any building that does not contain fire sprinklers are not comparable to high-rise office buildings with fire sprinklers. Additionally, any deaths in stairwells without stairwell pressurization cannot be delineated as preventable by a UBC 1991 code "smoke control" system.
Study ConclusionThe data presented in the NFPA report clearly delineates the need for fire sprinklers. According to this information, the installation of fire sprinklers greatly reduces the damage and eliminates the risk of death due to fire in high-rise office buildings. This article also fully supports stairwell pressurization and a smoke evacuation system (either through knockout windows or through mechanical means).
Based upon this data, it seems the need for smoke control systems is no longer present. The International Building Code (IBC 2000) does not even include the requirement for smoke control for high-rise office buildings. Requiring smoke control systems in high-rise office buildings ignores the data and misplaces the public's trust in the code making bodies.
It should always be an owner's intent to protect the health and safety of the property's occupants. However, no one wants to install a system, especially at a high cost, that is of very little, if any, benefit to the occupants during a fire. Instead, protect the public by requiring fire sprinklers in residential buildings. This will truly save lives, as opposed to this ill-advised code for high-rise office buildings that already provide adequate safety to the occupants.