Inspection Protocol And Test Procedures; General Objective; Legal And Technical Authorities - Gemini 501-B User Manual

Smoke detectors sensitivity analyzer

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5.0 Inspection Protocol and Test Procedures

5.1

The Gemini 501-B Analyzer was designed to perform on-site inspections of installed smoke detectors to

determine their sensitivities. Sensitivity is defined as the amount (concentration in mg/m 3 or obscuration in

%/ft) of smoke needed to trigger the alarm of the detector under test.

Normally only a single test is needed for routine sensitivity inspection of detectors. To assure such an

outcome, choose a smoke concentration at the upper limit of the sensitivity range specified by the

manufacturer (usually located on the back of the smoke detector). The detector should alarm since it is

statistically the highest concentration allowable by the manufacturer. However, if the above detector did not

alarm, you have to do additional tests to determine the concentration that would trigger the detector.

In cases where the detector has a history of nuisance (false) alarm, you may have to do two or more tests to

find the lowest concentration level below which the detector would not alarm.

Figure 2 (page 12) contains an example in selecting the smoke concentration settings for sensitivity tests

under the NFPA 72 National Fire Alarm Code (1996) requirements. To get higher test precision than the

routine inspection requirement, use an increment of 0.2 %/ft instead of 0.5 %/ft. You may also want to

establish other test criteria by consulting with your state Fire Marshall and manufacturers to fit your own

needs and resource. Record all data by using either the sample test report in APPENDIX C or your own

recording method.

5.2

Smoke detector inspection and sensitivity testing techniques are based ONLY on the following three

recognized authorities:

The National Fire Protection Association (NFPA) publishes the NFPA 72 National Fire Alarm Code (1996). It

recommends evaluation of smoke detector sensitivity within one year after installation and every

alternate year thereafter. The recommended test methods include the use of smoke aerosol and

calibrated sensitivity test instrument to verify the approved or manufacturer specified sensitivity

range.

Underwriters Laboratories, through its UL-268 standard, considers detectors to be acceptable if its sensitivity

are between 0.5 to 4.0 %/ft obscuration when exposed to the visible (gray) smoke in a UL smoke

chamber. This standard applies only if the manufacturer has not specified the sensitivity range.

Authority Having Jurisdiction (AHJ). The Fire Marshal or Fire Chief at the state or local level is responsible

for enforcing their published standards or codes. These standards generally follow some national

standards with or without modification to suit the local need. For example, the Boston Fire

Department requires detectors located in elevator waiting areas to meet a sensitivity of 3.0 %/ft or

higher. This is to avoid frequent false alarms from smoldering cigarettes that passengers leave prior

to boarding the elevators.

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