Putting Smoke Detectors to the Test

Last month, we discussed some of the ins and outs associated with the installation of automatic smoke detectors. This month, my goal is to cover testing — including the sometimes misunderstood sensitivity, or calibration, test.

We’ll look at why sensitivity tests are necessary and we’ll examine some of the issues surrounding implementation. 

2 Types Of Code-Compliant Testing

The first order of business is to understand the two basic types of code-compliant testing that fire alarm technicians commonly use. The most common testing method is referred to as functional and the less-often-used technique is referred to as calibration, or sensitivity, testing.

A functional test is one that involves a simple go/no-go response. It can be administered using an unmeasured amount of an airborne substance that mimics smoke.

This simulation can be created using a punk stick testing tool or by way of an aerosol that creates a fine mist. The latter, manufactured and listed for this purpose, comes in a small can that the technician holds up to the detector. When using this method, care must be taken not to administer the airborne mist too close to the detector. This is because the substance emitted is wet and sticky when it first exits the can. After a short time it will dry, thus not adhering to any of the innards within the smoke detector when it comes into contact.

Another method used by some manufacturers involves the use of a two-sided plastic card that the fire technician inserts into a slot in the detector. Insert one end and the detector goes into alarm. Insert the other end and it shouldn’t do anything. If it does sound a trouble condition, the tech knows he has a problem with the detector. 

Another method is to administer a magnet that comes with the detector. When the technician holds the magnet up to the detector, an alarm should sound. Still yet another involves exposing the smoke detector to a television infrared remote (any TV remote). The presence of an IR signal prompts the detector to conduct an internal test.

The often-misunderstood sensitivity test entails the use of a measured substance that acts to test a smoke detector’s ability to respond to smoke. Because it’s measured, the sensitivity tester can determine just how much or little smoke it requires to generate an alarm. Another method is to use a manufacturer-specific testing device that can perform a calibration test internal to the detector.

Sensitivity testing centers on a percentage that must be logged by the fire technician. It relates to the obscuration of smoke in the smoke detector sensing chamber. Functional smoke detector tests are the most common and they fill the purpose of smoke detector testing most of the time.

Testing Frequency Per NFPA 72

According to Table, NFPA 72, 2007 Edition, the test frequency of a common smoke detector is: 1) when it’s installed, and 2) on an annual basis thereafter. The same testing criteria pertains to single- and multiple-station smoke alarms (Table[j]).

Testing also is required when conducting reacceptance tests, meaning that when a system design is altered and additional detectors installed or some removed, or when a system undergoes major repairs or detector replacement, testing of the smoke detectors and other affected areas is required.

There are several exceptions to this rule. First, where a smoke detector is part of industrial processing equipment or some other situation where a number of smoke detectors are not inaccessible to the fire alarm technician. In this case, Section 10.4.4, NFPA 72, 2007, allows a six-month grace period, or up to 18 months per inspection — this is providing the authority having jurisdiction (AHJ) is in agreement with the delay.

The other exception, as specified by Section, involves the use of remotely monitored fire alarm systems that monitor and test connected smoke detectors. “If automatic testing is performed at least weekly by a remotely monitored fire alarm control unit specifically listed for the application, the manual testing frequency shall be permitted to be extended to annually. Table 10.4.4 shall apply.”

This is a common method of operation in analog addressable fire alarm systems. This type of system is capable of determining when a detector is out of compliance. Because it is monitored by either a central station or supervisory station, someone is alerted almost as soon as the problem is detected.

There are two basic methods of testing smoke detector calibration. One uses a manufacturer-specific testing device designed for a specific make/model. The other consists of a generic testing device that will test anyone’s smoke detector.

Sensitivity testing is conducted when the fire alarm system is first installed and then every year thereafter. Where the smoke detectors in a facility passes several years in a row, NFPA 72 allows the testing frequency to be extended to every five years, providing a detailed record of all false alarms and other issues is kept on each detector in the system. For more information on sensitivity testing, see the sidebar.                                 

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