Are Roof Vents Effective Fire Protection?
By Richard Schulte
Schulte & Associates, Evanston, Ill.
The Summer 2006 issue of the newsletter published by the American Architectural Manufacturers Association (AAMA), AAMAnet.work, includes a short article titled “Smoke and Heat Vent Simulations to Begin”. This article includes the following excerpts:
“. . . Others in the code arena, however, have sought to reduce construction costs by eliminating code requirements for S&HV [smoke and heat vents] in buildings that include automatic sprinkler systems. The opponents' bottom line: smoke/heat vents are not cost-effective in buildings with sprinklers and should not be required. This has been an area of controversy for some time.”
“To concretely demonstrate the value of S&HV in terms of property protection, occupant safety, firefighter safety, and firefighter effectiveness, AAMA's Smoke Vent Task Group (SVTG) has inked a contract with Hughes and Associates to conduct Large Eddy Simulation (LES) and Computational Fluid Dynamics (CFD) studies. . . “
While some fire protection field may be opposed to the installation of smoke/heat vents in buildings protected by standard spray sprinklers based solely upon cost and cost effectiveness, other fire protection professionals are opposed to the installation of vents because automatic roof vents are simply ineffective in venting heat and smoke in sprinklered buildings. Of course, if vents are ineffective, then it's likely that vents are also “not cost-effective”.
What is the basis for the opinion that smoke/heat vents are ineffective in buildings protected by standard spray sprinklers? Consider the following statements made by Dr. Craig Beyler of Hughes Associates Inc. in recent years:
“The experimental studies have shown that . . . . .current design practices are likely to limit the number of vents operated to one and vents may in fact not operate at all in very successful sprinkler operations.”(1)
“Not only is the fear of early operation not founded, current design practice will likely lead to 0-1 vents operating”(2)
“Eliminates Need for Manual Venting? No”(2)
“Vents don't always open and never open as many as might be wanted.”(2)
“Reduces Heat and Smoke Damage? Unknown”(2)
“There is a movement to use smoke vents without draft curtains There is no R&D basis for this approach”(2)
“Revised design methods for early operation of vents are needed”(2)
The basis for Dr. Beyler's opinions above is the research and testing of the interaction between standard spray sprinklers and roof vents sponsored by the National Fire Protection Research Foundation (NFPRF) and conducted at Underwriters Laboratories in Northbrook, IL, in 1997 and 1998. Obviously, if smoke/heat vents don't automatically open in sprinklered buildings (where the sprinkler system is operational and adequate for the hazard), little or no venting will occur prior to the arrival of the fire department.
The scenarios where automatic roof vents could potentially be effective are where the sprinkler system is operational, but inadequate for the hazard protected, or where the sprinkler system fails to discharge water due to an impaired water supply (i.e., a closed water supply valve, broken supply piping or the failure of a pump to start). The effectiveness of automatic smoke/heat vents in the first scenario was called into question by a fire which occurred in a bulk retail facility in Tempe, AZ, on March 19, 1998. In this fire, the sprinkler design was based upon the assumption that 29 high temperature large orifice standard sprinklers would activate, however, 66 sprinklers actually operated. Although the building was provided with 29 automatic smoke/heat vents and draft curtains as required by the Uniform Fire Code, the 100,000 square foot building was filled with smoke from floor to the underside of the roof when the fire department arrived at the scene. In other words, the smoke/heat vents failed to perform their basic function in this scenario.
In the scenario where the sprinkler system fails due to an impaired water supply, the value of smoke/heat vents is totally dependent upon the capabilities of the responding fire department to conduct interior manual firefighting operations without the assistance of sprinkler protection.
The capabilities of U.S. fire departments is addressed in a report issued by the U.S. Fire Administration (USFA) in October 2006 titled “Four Years Later-A Second Needs Assessment of the U.S. Fire Service”. This report calls into question whether many U.S. fire departments are capable of safely conducting interior manual firefighting operations in any building where the sprinkler protection has failed, much less large industrial or storage buildings. Excerpts from the USFA report include the following:
“In communities with less than 2,500 population, 21% of fire departments, nearly all of them all-or mostly-volunteer departments, deliver an average of 4 or fewer volunteer fire-fighters to a mid-day house fire. . . . it is likely that most of these departments often fail to deliver the minimum of 4 firefighters recognized by national standards as the necessary minimum for interior fire attack.”
“An estimated 128,000 firefighters, most of them volunteers serving in communities with less than 2,500 population, serve in departments that are involved in structural firefighting but have not certified any firefighters to Firefighter Level I or II.”
“An estimated 79,000 firefighters serve in fire departments that protect communities of at least 50,000 population and have fewer than 4 career firefighters assigned to first-due engine companies. It is likely that, for many of these departments, the first arriving complement of firefighters often falls short of the minimum of 4 firefighters needed to initiate an interior attack on a structure fire, thereby requiring the first-arriving firefighters to wait until the rest of the first-alarm responders arrive.”
“An estimated 737,000 firefighters serve in fire departments with no program to maintain basic firefighter fitness and health, most of them volunteers serving communities with less than 5,000 population.”
“Roughly 14,000 fire engines (pumpers) (17% of all engines) are 15 to 19 years old, another 15,700 (19%) are 20 to 29 years old, and 10,900 (13%) are at least 30 years old. Therefore, roughly half (49%) of all engines are at least 15 years old.”
“An estimated 65% of fire departments do not have enough portable radios to equip all emergency responders on a shift. The percentage of departments that cannot provide radios to all emergency responders on a shift is highest for communities under 2,500 population.”
An estimated 60% of fire departments do not have enough self-contained breathing apparatus (SCBA) to equip all firefighters on a shift.”
“An estimated half (48%) of fire departments do not have enough personal alert system (PASS) devices to equip all emergency responders on a shift.”
“Even a rural community can have a large factory complex, a large stadium, or even a high-rise building, with all the technical complexities and potential for high concentration of people or valued property that such a property entails.”
The capabilities of the fire service in the U.S. is also addressed in a press release from the House [of Representatives] Committee on Science and Technology dated Nov. 7, 2003. Excerpts from this press release include the following:
“Further, the International Association of Fire Chiefs (IAFC) has estimated that 2/3 of America's fire departments do not meet the National Fire Protection Association (NFPA) staffing standards. These situations endanger firefighters as well as the citizens they protect.
“Many local communities across America, facing difficult budget times, have been forced to cut fire department budgets, often eliminating essential firefighter positions.”
The supporting statement for Code Change RB4-06/07 to the International Residential Code submitted by Joseph Finnegan, representing the Firemen's Association of the state of New York, also provides further evidence of the lack of capabilities of even paid fire departments. Finnegan's supporting statement contains the following excerpt:
“Sufficient resources required to provide safe manual fire suppression activities are not currently available in most municipalities defended by full time firefighting personnel.”
Given the above, it's not too difficult to conclude that the protection provided by smoke/heat vents is essentially useless from a firefighting standpoint in the event of a sprinkler system failure.
Conclusions
The following summarizes the operation of smoke/heat vents in buildings protected by standard spray sprinklers under the various sprinkler operation scenarios:
“The NFPRF research (1997/1998) demonstrated that automatic smoke/heat vents are unlikely to open in storage occupancies protected by standard spray sprinklers where the sprinkler system is operable and adequate for the hazard.
“The bulk retail facility fire in Tempe, AZ, on March 19, 1998 demonstrated that smoke/heat vents may not perform their intended function in the event that the sprinkler system is operable, but fails to control the fire.
“Based on the USFA report on the capabilities of U.S. fire departments (and a number of other sources), many, if not most fire departments lack the resources to safely conduct interior manual firefighting operations in large industrial and storage buildings in the event of the failure of the sprinkler system.
Why does the International Building Code still require smoke/heat vents in industrial and storage buildings protected by standard spray sprinklers? In my opinion, the answer to this question is that the vent manufacturers have done an excellent job of “hood-winking” the fire service into thinking that smoke/heat vents will actually assist manual interior firefighting operations in sprinklered buildings.
Resources
1. Executive Summary, “Interaction of Sprinklers With Smoke and Heat Vents”, Craig L. Beyler and Leonard Y. Cooper, February 1999.
2. “Sprinkler/Vent Interaction, What People Think, What We Know and What We Don't”, Dr. Craig Beyler (undated presentation). This presentation can be found by clicking here.
Richard Schulte is a 1976 graduate of the fire protection engineering program at the Illinois Institute of Technology. After working in various positions within the fire protection field, he formed Schulte & Associates in 1988. His consulting experience includes work on the Sears Tower and numerous other notable structures. He has also acted as an expert witness in the litigation involving the fire at the New Orleans Distribution Center. He can be contacted by sending e-mail to rschulte@plumbingengineer.com.