A Look at the Smoke Detector Listing Process

Compatibility is something with which anyone who installs code-compliant fire alarm systems must be concerned. Unless one manufacturer’s smoke detector is listed as compatible with another manufacturer’s fire alarm control panel, the two should not be connected together to form a system. This is especially critical in the area of two-wire smoke detectors that derive their operating power from the same two conductors that provide detection.

“All detection devices that receive their power from the initiating device circuit or signaling line circuit of a control unit shall be listed for use with the control unit” (Section 4.4.2, NFPA 72, National Electric Code, 2007 Edition). The issue of deriving power from the initiating circuit is of great importance from a standpoint of available power.

When connected devices haven’t been tested for compatibility there is no guarantee that when a smoke detector activates it will trip the alarm control panel. Another concern is it might draw too much power, thus preventing other initiating devices from activating.

Another concern is whether a new smoke detector actually meets NFPA 72 standards as well as those of a third-party testing company. For one thing, this means new smoke detectors must comply with Section 5.7.2, 2007 Edition, as well as others. Here, performance-related criteria is highlighted that must be included in the engineering and fabrication of all new smoke detectors.

This month, we’ll look at what it takes to assure compatibility of smoke detectors by way of a third-party testing facility, such as Underwriters Laboratories (UL) of Northbrook, Ill., or FM Global of Johnston, R.I. 

Assuring Compatibility

The first step in the testing procedure is for the smoke detector manufacturer to design its device to work with a specific fire alarm control panel. This usually means the manufacturer must conduct internal tests to assure compatibility. Once this is done, it’s time to submit the smoke detector along with the   intended fire alarm panel for intense review by an unbiased, third-party testing facility.

Before that takes place it’s common for the manufacturer to request a formal quote for the testing procedure from the testing organization (e.g. FM or UL).

“We always request a quote from UL before we begin the testing process,” says Andrej Nikolic, regulatory compliance manager with System Sensor of St. Charles, Ill. “Then, when we receive the quote we evaluate the details, discuss any questions we may have with UL, and we then usually submit our samples for testing.”

The overall cost associated with testing a new smoke detector can range from $31,000 to $45,000.

“Our quote provides the customer with information on cost, estimated time to complete the project, the number of samples needed, a detailed test plan and other information that may be required,” says John Drengenbert, consumer affairs manager for UL.

According to Nikolic, around 30 detector samples are required for UL to perform the full test program. In addition, a core set of documents must be submitted for review.

Time Is of the Essence

The testing process requires a good deal of preparation as UL works to assure the smoke detectors work properly with the submitted alarm panel. From start to finish, it can take many weeks before the manufacturer knows whether its detector has passed UL standards or not.

“The typical time associated with one set of tests and a report is 12 to 16 weeks,” says Drengenbert. “Customers are kept informed of the status of the investigation as it progresses, and if unacceptable results occur they are notified as soon as possible.”

According to Nikolic, it can take upwards of 20 weeks. “We receive updates from UL on a regular basis. Generally, it has taken 18 to 20 weeks from the start of a project to learn whether the detector has passed all requirements.”

The listing process can take an additional four weeks, Nikolic says.

“Providing a typical time is rather difficult. In my experience, UL investigation is often used as a part of the manufacturer’s R&D process for the new detector,” says Drengenbert. “Since this results in the evaluation of a less than fully developed product, unacceptable test results are typically encountered.”

Problems can show up in any one of more than 50 separate testing procedures. When this takes place the manufacturer will usually make the necessary changes to correct the problem.

“These changes can lengthen the testing process at UL because, in addition to the test that produced the unacceptable results, other previously completed tests may need to be repeated due to the revisions made to the original design,” Drengenbert adds.

When the manufacturer is told a problem exists and is given the details, it can then take considerable time until those problems are corrected and additional samples can be provided. 

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