The commercial/industrial/institutional (CII) market presents many specific fire alarm system challenges. The commercial market represents occupancies including office, mercantile and multifamily residential buildings. The industrial market offers a relatively straightforward business opportunity. As you would expect, manufacturing occupancies prevail. And, the institutional market also presents a consistent business opportunity among occupancies such as hospitals, prisons and other institutions that provide care of some sort.
In each of these markets, the building and fire codes have specific minimum fire alarm system requirements. In the industrial market, a contractor must follow Occupational Safety and Health Administration (OSHA) regulations in addition to the building and fire codes. In some cases, the OSHA regulations may have stricter requirements than the building or fire codes.
The two central requirements for any fire alarm system installed in these occupancies are reliability and credibility.
Credible fire alarm systems are designed, installed and maintained to operate free of false alarms. If you have worked in the fire alarm industry for a while, you already know that the term “false alarm” has multiple definitions. In fact, NFPA 72 2010, the National Fire Alarm and Signaling Code, defines “nuisance alarm” as “Any alarm caused by mechanical failure, malfunction, improper installation, or lack of proper maintenance, or any alarm activated by a cause than cannot be determined.”
But, for purpose of this article, the term “false alarm” includes alarm activation from any nonfire condition. That means if a backdraft from a working fireplace causes a smoke detector near the fireplace to alarm, a false alarm has occurred. You may argue that the smoke detector just did its job by detecting the smoke. But, the fact remains that smoke did not represent a threat from a hostile fire. You may also argue that the code requires the smoke detector in the specific location, so no one can blame you for the false alarm.
Both of these arguments are wrong. With today’s technology, a system designer can and should account for adverse ambient conditions.
Of course, the first place to address potential false alarm issues is in the design stage. NFPA 72 2010 actually provides some guidance in this area. The guidance begins with the requirement to select and install devices “to minimize nuisance alarms.” And Section 22.214.171.124 further states that, “The selection and placement of smoke detectors shall take into account both the performance characteristics of the detector and the areas into which the detectors are to be installed to prevent nuisance alarms or improper operation after installation.”
Do these passages mean you should not install a smoke detector near a fireplace? Not necessarily. It means that you must choose the right technology for the application. In my fireplace example, a multicriteria smoke detector would be the correct device to use. This detector will detect smoke but will need to sense one other combustion product, such as heat or carbon monoxide, for example, before transmitting an alarm condition to the fire alarm control panel.
Some smoke detectors, typically the ionization type, will react to the products of combustion from cooking. Although this type of detector has applications in a fire alarm system design to maintain system credibility, you must not use them where you would expect products of cooking combustion.
The code specifically requires that, “Unless specifically designed and listed for the expected conditions, smoke detectors shall not be installed if any of the following ambient conditions exist:
“(1) Temperature below 32°F
“(2) Temperature above 100°F
“(3) Relative humidity above 93 percent
“(4) Air velocity greater than 300 ft./min.”
The code also requires that the system designer choose the location of smoke detectors based on an evaluation of potential ambient sources of smoke, moisture, dust or fumes, and electrical or mechanical influences. Doing so will minimize nuisance alarms.
If you follow these design requirements and understand the capabilities of the available detection devices that you can use in a fire alarm system design, you will help ensure a credible system design.
However, the design only deals with one-third of the reliability/-credibility equation. Reliable fire alarm systems begin with the appropriate system design and then derive from code-compliant installation and complete maintenance and testing programs after the installation.
The requirements in NFPA 72 2010 also will help you ensure a reliable and credible fire alarm system installation. First, you must install the fire alarm system in accordance with the specifications and standards approved by the authority having jurisdiction. This includes the National Fire Alarm and Signaling Code as well as any local or state codes.
Second, the code requires that you locate and mount devices and appliances to ensure that vibration and jarring do not cause accidental operation or failure. And, you can only install fire alarm system equipment in locations where conditions do not exceed the voltage, temperature and humidity limits specified in the manufacturer’s published instructions.
The code provides the minimum environmental conditions under which all fire alarm system equipment must operate and still perform their intended functions. These include the following:
“(1) At 85 percent and at 110 percent of the nameplate primary (main) and secondary (standby) input voltage(s)
“(2) At ambient temperatures of 32°F and 120°F
“(3) At a relative humidity of 85 percent and an ambient temperature of 86°F”
The annex states that “Product-listing standards include tests for temporary excursions beyond normal limits. In addition to temperature, humidity, and velocity variations, smoke detectors should operate reliably under such common environmental conditions as mechanical vibration, electrical interference, and other environmental influences … .”
With early smoke detector designs, you could not easily place them everywhere that the code required because of the devices’ sensitivity to minor environmental changes that would cause a false alarm. To counter this issue, manufacturers developed systems equipped with “alarm verification” features.
When enabled, this feature would permit the smoke detector to sense a minor transient change—such as someone walking underneath a smoke detector with a lit cigar or a flash of steam from a bathroom that would actuate a detector—-without initiating an alarm on the system.
Instead, the system would delay the alarm for one minute and attempt to reset the smoke detector so the system returned to normal and no alarm sounded. If, after the one-minute period, smoke continued to be present at the detector, then the alarm signal would transmit through the fire alarm system. The verification feature only applied to smoke detectors. If any other detection device—such as a heat detector or water flow switch—signaled an alarm condition, the system would operate without delay. In the 2010 edition of the code, a contractor may not initially enable the alarm verification feature unless conditions or occupant activities in the area of the smoke detector are expected to cause false alarms.
As stated in Annex A of the code, “The alarm verification feature should not be used as a substitute for proper detector location/applications or regular system maintenance. Alarm verification features are intended to reduce the frequency of false alarms caused by transient conditions.”
The alarm verification feature does not intend to compensate for design errors or lack of maintenance. As mentioned above, a better design practice would use a device such as a multicriteria smoke detector when the expected environmental condition might cause false alarms.
And finally, to help ensure the long-term reliability and credibility of a fire alarm system that uses smoke detection, the code requires protection of detectors during construction. It also requires that the contractor perform a specific test to verify that each smoke detector will operate in accordance with its listed and marked sensitivity. In lieu of this test, the contractor must replace the smoke detectors prior to the final commissioning of the system.
The professional contractor must understand the need to ensure reliability and credibility of the fire alarm systems he or she installs. It will help ensure the life safety of the occupants protected by the system.
MOORE, a licensed fire protection engineer, frequent speaker and an expert in the life safety field, is a past chair of the NFPA 72 Technical Correlating Committee. Moore is a principal with Hughes Associates Inc. at the Warwick, R.I., office. He can be reached at firstname.lastname@example.org.