Avoiding Smoke Detector Installation Problems

Fire alarm technicians know the value of the automatic smoke detectors they install. Unfortunately, some of us get into trouble when installing them because we fail to read our code books. In other cases, it’s not the fire technician at all that causes the trouble, but rather other unsuspecting tradesmen who may do something after the fact to interfere with the proper operation of the automatic initiation devices we install.

A good example of this recently occurred in a Pittsburgh nursing home where an electrician installed paddle fans too close to the smoke detectors.

“When the fire alarm inspector did a routine inspection, he brought the paddle fans to the attention of management. Because I am responsible for the ongoing operation of this system, they immediately called me about it,” says Nick Markowitz, owner of Markowitz Electric Protection of Verona, Pa. (see photo with print magazine edition of “Fire Side Chat”).

In Section of NFPA 72, National Fire Alarm Code Handbook, 2002 Edition, it states that fire technicians must carefully consider the selection and placement of all smoke detectors with regard to false alarms and improper operation. In Section, NFPA takes this one step further by stating where smoke detectors are not to be used. In this case, they are not to be used where the air velocity is greater than 300 feet per minute.

In Section A., it also states that smoke detectors are not to be installed in the path of a register’s air stream. A. goes further by providing a chart that correlates air movement with smoke detector spacing. Section 5.7.4 on HVAC systems also sets the spacing at 3 feet between smoke detectors and air registers and air diffusers.

An example cited in the comment section of Section involves the use of smoke detectors in computer rooms. Anyone who has worked in a computer room where the humidity and temperature are controlled knows all about air turbulence. In this case, the distance between smoke detectors must be drastically reduced to assure detection, per Table

In Markowitz’s case, one of three things needs to happen: He can install additional smoke detectors in the affected areas, move the affected smoke detectors to locations where air turbulence is minimal (while not affecting coverage), or the electrician can remove or move specific paddle fans so they do not create a problem.

Physical Protection for Smokes
Another consideration that fire technicians must observe is the physical integrity of the smoke detectors, fire pulls and notification appliances they install.

Concerning the protection of smoke and heat detectors, Section 5.4.2 of the National Fire Alarm Code Handbook, 2002, says, “Where subject to mechanical damage, an initiating device shall be protected. A mechanical guard used to protect a smoke or heat detector shall be listed for use with the detector.”

In the comment portion in the same section, it continues, “Mechanical damage can occur over an extended period of time from vibration, extremes in temperature, corrosive atmospheres, other chemical reactions or excessive humidity. The designer and installer must be sure that the initiating device will be appropriate for the environment in which it is to be installed.”

This is an important issue, especially when installing fire alarm systems in school buildings and other places where the public has access. The installer must also assure that the wire or plastic guard meets listed criteria by selecting a make/model listed by a third-party service specifically for use with the make/model smoke in use. Believe it or not, there are still device covers on the market that are not listed — avoid them to stay out of trouble.

Sources of False Alarms
Erroneous smoke detector activations are undoubtedly one of the largest problems that face the fire detection industry today. Overwhelmingly, fire departments across the country are overworked and have long ago lost their sense of patience in this regard.

The fire alarm industry has not been able to contain the problem and hostility among municipalities continues to grow by the year. Corrective action on the part of city fathers often consists of fines and penalties. Where the law enforcement community finally opted for a nonresponse cure for its false burglar alarms, fire departments may one day be forced to do the same — unless something is done.

Perhaps the best place to begin is the installation itself. Fire technicians must make absolutely sure that the mounting location of each and every detector is sound for the technology in use and any environmental factors that may be present, such as excessively high humidity.

According to Section of NFPA 72, National Fire Alarm Code Handbook, 2002, “The location of smoke detectors shall be based on an evaluation of potential ambient sources of smoke, moisture, dust, or fumes, and electrical or mechanical influences to minimize nuisance alarms.”

Begin by looking for sources of moisture, such as bathroom showers, live steam, humidifiers, slop sinks and more. Section cites a relative humidity of 93 percent as the cutoff mark for smoke detector use. Also, look for sources of temperature that could go above 100° F, as well as low temperatures below 32° F.

Installers should also inspect the environment for sources of false products of combustion, such as powerful cleaning chemicals, stoves and range tops, dryers, exhaust hoods, paint spraying and welding equipment.

Dust is another culprit that should be watched for because it is so common. Preventative measures, such as using canned air to periodically blow out smoke detectors, can help avoid false alarms. Engine exhaust and improperly ducted hot water tanks and furnaces can also cause false activations.

Monitoring 120V Tandem Smokes
Security dealers who make it a point to work in the new home market know very well how local code enforcement often requires the use of 120VAC smoke alarms with tandem line and battery back-up (9VDC) instead of system-type smoke detectors.

There is a way to comply while saving the client money. Security contractors can attach a relay to the smoke detector tandem line, through which they can monitor all the 120VAC smokes in the house at once.

In the old days, I would have reversed-engineered the tandem-line smoke detector. A simple industrial relay from a local supplier would have sufficed at the time, but not any more (see drawing print magazine edition of “Fire Side Chat”).

Today, anything you attach to a smoke detector must be listed for use with the detector in question. If it’s not, then your installation is out of compliance.

“Equipment constructed and installed in conformity with this code shall be listed for the purpose for which it is used. Fire alarm system components shall be installed in accordance with the manufacturers’ installation instructions” (Section 4.3.1, NFPA 72 National Fire Alarm Handbook, 2002).

When we talk about a fire alarm component being “listed,” what we mean is that an independent third-party firm — such as UL in Buffalo Grove, Ill. — has tested the component and that it has been found compatible with specific devices, which will be listed by the testing organization.

The component will then receive a listing from this third-party entity that specifically names the devices for which it was found to be compatible. For more information on such listings, see Section 3.2.5 of NFPA 72, 2002.

In the case of the 120VAC tandem-line smoke alarm connection, a specific relay module is necessary to comply with code. In every case I have seen, the manufacturer will have one.


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