Safeguarding Historic Structures With Advanced Smoke Detection

By Del Williams

Landmarks aren’t spared the risks of and potential damage caused by fire. This means many of the world’s historic, cultural and architectural treasures – such as cathedrals, museums, and capitol buildings – are at risk of being damaged, forever lost to fire. Society must do all that it can to protect and preserve them.

When such structures are hundreds of years old and not designed with smoke detection or fire suppression in mind, that task can be challenging. The high ceilings and voluminous spaces in cathedrals and grand halls that inspire awe with their beauty, ironically, are the most difficult to protect with traditional smoke detection.

Fortunately, today’s technological innovations can enable superior early smoke detection of areas without compromising beautiful, historic aesthetics with intrusive, anachronistic, ceiling mounts or wiring. The latest beam detectors, called Open-area Smoke Imaging Detection (OSID), can monitor the attenuation of optical beams and be installed below the ceiling to conform with architectural features of a structure. Unlike typical spot smoke detectors, which are placed in multiple locations, beam detectors can identify smoke particles over large, continuous areas, minimizing the need for numerous detection devices, wiring and conduit.

The latest generation of these beam detectors is also designed to be very reliable, capable of distinguishing between smoke, dust, and other particles, as well as resistant to false alarms and faults due to building movement. Easy installation and maintenance are also distinguishing qualities. These systems can be installed in easy-to-access locations below the ceiling to accommodate and to conform to the features of the building.

Protecting Cathedral Basilica Of The Sacred Heart

The Cathedral Basilica of the Sacred Heart in Newark, NJ, is the fifth-largest cathedral in North America and the seat of the Roman Catholic Archdiocese of Newark. Construction of the French Gothic Revival style cathedral began in 1899, finished in 1954, and today it is listed on the U.S. National Register of Historic Places. (See a virtual tour of The Cathedral Basilica of the Sacred Heart here.)

When Cathedral Basilica recently updated its security and fire protection, NJ-based United Fire Protection Corp., one of the largest, full-service fire protection companies in the New York metro area, was charged with the task. The scope of the project involved fire detection and an alarm system installation throughout the cathedral, its offices and residential areas. While the offices and residential areas primarily used traditional spot smoke detectors, this was not feasible in the cathedral’s resplendent, high-ceiling sanctuary, which required advanced fire detection to solve the smoke detection challenge.

“The challenge was providing superior early warning fire detection without detracting from the aesthetics of the cathedral sanctuary in any way,” said Frank Savino, president of United Fire Protection.

For such high-ceiling applications, using heat detection would be ineffective, according to Savino. “By the time heat detectors would alarm at an elevation of 50 feet or more, the fire size would be big and significant smoke and fire damage would have already occurred,” he said.

Installing spot smoke detection or air sampling system would mean placing smoke detectors on the ceiling, but installing that technology on vaulted, archway ceilings would detract from the beauty of the building. That was not an option.

It is not just the device itself but also conduit and wiring that can compromise aesthetics. The goal was to install an invisible smoke detection system that did not impact the aesthetics of the building in any way.

To resolve these challenges, Savino turned to a sophisticated type of smoke detection system designed specifically for large open spaces: OSID by Honeywell, a global leader in fire and life safety products.

Essentially, the system uses imaging technology to monitor the modulation of light beams disrupted by smoke particles between components that can be located hundreds of feet apart. It uses a CMOS imager, an electronic chip that converts light photons to electrons for digital processing, that is the equivalent of hundreds of thousands of photocells, which far surpasses the detection capability of a single photo receiver.

“In its basic configuration, OSID-R (Reflective) uses an emitter and an imager,” according to Khaleel Rehman, director of development for the advanced detection fire team, Honeywell. “It operates on the principle of light obscuration, using an ultraviolet and an infrared (IR) beam. When smoke partially blocks the beam, an alarm is activated. Because power and connectivity occur in the imager only, the device only requires a single unobtrusive reflector on the opposite wall.”

“The key benefit of the OSID system for Cathedral Basilica is the ability to provide early fire detection of the wide-open spaces of the sanctuary efficiently,” said Savino. “In fact, it actually detects smoke faster and better if installed lower than at ceiling level.”

Instead of ceiling mounts, Savino was able to install four advanced OSID beam detectors in an electro-mechanical access space along the cathedral’s triforium, a walkway around the perimeter of the cathedral. Installing them there meant that they were out of sight from the cathedral floor level.

This allows the beams to project invisibly from one side of the cathedral to the other side, and smoke passing anywhere in the path of the beam will initiate an alarm. For this application, a dual-ended version of OSID using a reflector installed on the opposing wall saved on installation cost because wiring was only required on one end.

“A high-power OSID system can provide effective, continuous detection of smoke particles for approximately 500 feet,” said Savino. “Advanced beam detection also offers the advantage of continuous detection along its entire projected length. It is like having a continuous line of spot smoke detectors installed a foot apart. Smoke intrusion anywhere along this path would activate an alarm.”

Compared to previous generations of beam detection, the advanced devices are far more reliable. Today, CMOS imagers find and lock on to their detection target (reflector or emitter), eliminating building movement issues, which causes legacy projected beam detection to go out of alignment. The CMOS imager further minimizes fault and nuisance alarms from solid object intrusion and dust. OSID’s dual spectrum beam using both ultraviolet and IR can discriminate between real smoke from fire versus non-fire sources.

Savino and United Fire Protection Corp. successfully completed installation of the OSID system. In the long run, he believes that it also offers significant advantages for required periodic testing as well.

As beam detectors do not have to be mounted on the ceilings, periodic code required inspection, test, and maintenance is easy with OSID.

According to Savino, “Annual testing with OSID is quick and easy. Essentially, we just put a test filter that simulates real smoke in front of the beam, which simulates a smoke condition. We can do that in the electro-mechanical access space along the cathedral’s triforium. That is much easier and safer than having to go up in a lift to blow smoke into spot detectors on a high ceiling.”

From Savino’s decades of experience as a fire safety professional, he concludes that for historic structures with high ceilings and substantial open spaces, this approach simply makes sense.

“We need to protect our irreplaceable, architectural treasures and all the culture and history they contain without compromising their aesthetics in the process,” he said. “Today, that often is best accomplished in vast, high open spaces with OSID, which is becoming a best practice fire protection technique in these situations.”

Del Williams is a technical writer based in Torrance, CA.