Tunnel fire safety experts get sprinkler religion
A year ago, after submitting sprinkler system bid documents for the new medical center at Wossamotta University in Frostbite Falls, I was called upon by the hospital architect, Mr. Noitall, to defend my design. He demanded, “Why did you provide sprinklers protection in the operating, delivery, cardiac, X-ray and intensive care rooms and patient sleeping rooms?” I proceeded to explain, “Well gee Mr. Know-it-all, we were trying to meet the requirement for a fully sprinklered facility.” He replied, “Didn’t you know that these areas are exempted from the sprinklers by the building code?” He then showed me the following passage from the 1985 edition of the Uniform Building Code.
Section 3802(g) Group I Occupancies. An automatic sprinkler system shall be installed in Group I Occupancies.
EXCEPTIONS: 1. In hospitals of Types I, II Fire-resistive and II One-hour construction, the automatic sprinkler system may be omitted from operating, delivery, cardiac, X-ray and intensive care rooms and patient sleeping rooms not exceeding 450 square feet in area when each such room is provided with smoke detectors connected to a continuously attended station or location within the building. Increases for area and height specified in Sections 506 (c) and 507 shall not apply when this exception is used.
He proceeded to chide me further, “Don’t you know that sprinklers in these areas will endanger the safety of the patients? There may high voltage electrical equipment and, even worse, all that dirty sprinkler water could infect the patients! Besides, we have smoke detectors.”
Resistance to sprinklers in the name of safety has been a recurring theme. The first NFPA document dealing with fire protection for road tunnels was the 1980 edition of NFPA 502 Recommended Practice on Fire Protection for Limited Access Highways, Tunnels, Bridges, Elevated Roadways, and Air Right Structures. In 1998, the document became a standard and included the first information on fixed fire suppression systems, i.e. water based suppression. Unfortunately, the information was not exactly pro-sprinkler. Paragraph D-1.2 lists the “major concerns expressed by tunnel authorities regarding fire sprinkler use and effectiveness.” Included among the concerns are the following:
(e) Even a light spray from sprinklers can catch motorists unaware and can exceed that which windshield wipers could clear. Sprinkler discharge can also cause the roadway to become dangerously slippery.
(f) Water that sprays from the ceiling of a subaqueous tunnel suggests tunnel failure and can induce panic in motorists. (Oh my! The “P” word)
(g) The use of sprinklers can cause the delamination of the smoke layer and induce turbulence and mixing of the air and smoke, thus threatening the safety of motorists in the tunnel.
Paragraph D-2 of this Appendix goes on to recommend that sprinkler protection “should be considered applicable only where the passage of hazardous cargo is considered.” Paragraph D-4 seals the deal by recommending provisions to render any presence of sprinklers ineffective. It states:
To ensure against accidental discharge, the sprinkler system should be designed as a manually activated deluge system.
Harken back to the 1985 edition of the UBC. Exception 2 to paragraph 3802(g) states:
2. In jails, prisons and reformatories, the piping system may be dry, provided a manually operated valve is installed at a continuously monitored location. Opening of the valve will cause the piping system to be charged.
Hmmm, must not let the prisoners get wet, no that would not do.
The “concerns” about sprinklers remained in NFPA 502 through 2008 edition of the standard. However, the 2008 edition included with each of the concerns a short statement fully refuting each of the concerns. For example, regarding the reference to panic, it is stated:
This theoretical concern was not borne out in practice. In the event of fire, motorists are likely to recognize water spraying from nozzles as a fire safety measure. Behavioral studies have shown that most people do not panic in a fire, even when they are unable to see.
The development of tunnel fire protection measures in the U.S. parallels that of the Europe. And, we all know how Europeans feel about sprinklers. The World Road Association, known by the acronym PIARC, develops and publishes consensus standard documents used by many European nations as the basis for tunnel fire safety.
The 1999 PIARC publication, Fire and Smoke Control in Road Tunnels, summarized the concerns with use of fixed systems. Points made were:
• Water can cause explosion in petrol and other chemical substances if not combined with appropriate additives.
• There is a risk that the fire is extinguished, but flammable gases are still produced and may cause an explosion.
• Vaporised steam can hurt people.
• The efficiency is low for fires inside vehicles.
• The smoke layer is cooled down and de-stratified, so that it will cover the whole tunnel.
• Maintenance can be costly.
• Sprinklers are difficult to handle manually.
• Visibility is reduced.
Based on this the PIARC document concludes:
As a consequence, sprinklers must not be started before all people have evacuated. Based on these facts, sprinklers cannot be considered as an equipment useful to save lives. They can only be used to protect the tunnel once evacuation is completed. Taking into account this exclusively economic aim (protection of property and not safety), sprinklers are generally not considered as cost-effective and are not recommended in usual road tunnels.
Not all nations were late to the sprinkler party. Japan has been successfully providing fixed fire suppression systems in tunnels for more than 40 years. Australia also has many tunnels equipped with fixed suppression.
As in the U.S. with NFPA 502, a change in European attitudes on fixed fire suppression systems is reflected in the 2008 PIARC publication, Road Tunnels: An Assessment of Fixed Fire Fighting Systems. On examining prior road tunnel fires, the following common factors were noted:
• Fires develop much more quickly than expected.
• Fire temperatures in excess of 1,000°C can be achieved.
• Smoke volumes during the early stages of fire are greater than expected.
• Fire spread between vehicles occurs over a much greater distance than expected (e.g. more than 200 meters in the Mont Blanc Tunnel).
• The behaviour of tunnel users was unexpected in that they did not realize the amount of danger they were in, and chose to stay in their vehicles during the early stages of fire. They did not want to leave their property and mistakenly believed that they were safer in their cars than by using the self-rescue safety systems. By the time they realized the danger they were in, it was too late to self-rescue.
In a somewhat timid and limited concession to the value of fixed fire suppression systems, the document goes on to admit the following.
These observations indicate that there are numerous opportunities for improving tunnel safety following a fire incident. In order to satisfactorily embrace these opportunities, consideration of (fixed firefighting systems) may in some circumstances be warranted.
There were several reasons explaining the about-face on fixed suppression. In the case of NFPA 502, two new members of the technical committee drove the change: Alan Brinson, representing the International Sprinkler Association, and David J. LeBlanc, of Tyco Fire & Building Products. Both are still on the committee. It appears the Mr. Brinson was influential on the European front also.
Another reason for the change was a series of deadly tunnel fires, which occurred between 1999 and 2001. Five tunnel fires, all in Europe, resulted in 72 deaths. The most notable fire was the 1999 Mount Blanc Tunnel, seven miles long connecting France and Italy, in which 39 persons died.
Yet, another reason spurring interested in active protection is the desire to permit tunnel use by vehicles containing “hazardous cargos.” Many tunnels have prohibitions on the use by vehicles carrying hazardous cargo, something that is difficult to police, and which places a severe burden on commerce. The Colorado Department of Transportation recently bid a project to retrofit fixed fire suppression systems in the Eisenhower Johnson Memorial Tunnel. Interstate I-70 passes through this tunnel, which is near Denver and is approximately 1.7 miles long. A major reason for the project is to allow hazardous cargo to be transported through the tunnel.
Developments in fixed fire suppression technology, most notably water mist systems, have also made protection of tunnels more feasible. Since 1999, there has been a significant increase in research on tunnel fixed suppression systems. A look at the proceedings from the International Symposia on Tunnel Safety and Security, (Stockholm 2008, Frankfurt 2010, New York 2012) reveals many articles involving new research on active fire protection.
The research along with information from case histories involving fires in sprinklered tunnels shows that fixed fire suppression systems:
• Keep fire small
• Smaller fires lead to less smoke production allowing improved performance of ventilation systems
• Limit damage to the tunnel structure
• Limit fire spread between vehicles
• Improve chances of unassisted evacuation of tunnel occupants
The fire in Melbourne, Australia’s Burnley tunnel in March 2007 is a case in point. The fire started with a traffic accident involving four cars and three heavy goods vehicles. The tunnel was protected with manually activated deluge systems. The systems were activated early in the event and kept the fire under control while occupants evacuated the tunnel and fire fighters arrived to complete extinguishment. Despite a potentially huge fire, estimated at 10 MW at onset, and the presence of over 400 people in the tunnel, only three people died. The victims were killed in the traffic accident, not the subsequent fire. The tunnel reopened for business four days later. Much credit for the performance was early activation of the system and the performance of the ventilation system.
If I may be so bold as to make a prediction, I believe within a few short years fixed fire suppression systems will be an essential feature in the fire safety engineering approach to tunnel fire protection. On occasion this columnist could be accused of exercising 20-20 hindsight. Well, when one has been around as long as I have, one develops a huge amount of hind for which to sight. I just find it interesting that the tunnel fire experts are coming to the same conclusions about water based fixed fire suppression systems that the pro-sprinkler crowd has be espousing in general application for decades. Besides, I was a fan of Bullwinkle before he was a movie star.
Samuel S. Dannaway, PE, is a registered fire protection engineer and mechanical engineer with bachelor’s and master’s degrees from the University of Maryland Department of Fire Protection Engineering. He is past president and a Fellow of the Society of Fire Protection Engineers. He is president of S. S. Dannaway Associates Inc., a 15-person fire protection engineering firm with offices in Honolulu and Guam. He can be reached via email at SDannaway@ssdafire.com.