d) The low maintenance requirements and high reliability of grid
wire sensors are also important trade-off considerations.
e) The relatively high cost of installation (man-hours) is an
important consideration in tradeoffs by the security system designer in
selection of grid wire sensor versus another type for a specific
18.104.22.168 Protection of Utility Inlets/Openings. This application is
normally accomplished by the configuration of a breakwire sensor in a
laced "wire trap configuration or by the use of volumetric sensors. The use
of "wire traps" for this application is discussed in paragraph titled
"Breakwire." The considerations for application and installation discussed
therein apply. Other considerations are:
a) Sensor type selection and application are dictated by what is
passing through the utility inlet/opening (cable, air, fluid, etc.).
b) The application of volumetric sensors to utility outlets, such
as duct work, is not advised due to the high nuisance alarm rate caused by
the environmental control system (airflow, etc.). Volumetric sensors are
usually most cost effective for protection of false ceilings, raised
flooring, and other relatively benign spaces.
The protection of utility inlets/openings should include