In last month’s “Fire Side Chat,” we discussed the dangers associated with carbon monoxide (CO) in the workplace and the home. We also talked about CO detection and some of the considerations that fire technicians and security dealers must make before installing a CO detector.
This month, we will delve further into the fine points of CO detector installation. This will include a bird’s-eye view of a CO detection system that will:
- Interface to a conventional alarm system, burglar, fire or combination burglar/fire
- Shut down the furnace or other carbon monoxide-producing equipment in the home
The Powers Behind CO Detection
There are several types of CO detectors on the market today. These detectors differ in how they detect CO, how they derive operating power and how they integrate with a central control system.
Operating power is probably the first consideration the installer must address. For example, in the do-it-yourself realm there is the single-station CO detector that derives power from an internal battery or the public electric bus.
The latter usually is achieved via a pigtail connection or by the insertion of a male plug into a duplex receptacle. Those powered by an internal battery are usually installed by the homeowner, while a professional installs the publicly powered detectors.
Another source of power is DC, which is often provided by an auxiliary power supply or a central control system, such as an alarm control panel.
When this power method is used, it is usually assumed that the CO detector(s) will interconnect with a central head-end system of some kind. This will enable the detection of CO to result in more than simply a local alarm at an individual device.
A central head-end will not only alert all occupants of a problem simultaneously, but also summon outside help through a distinctly different outdoor sounder, a voice dialer or central station monitoring, which is where the fire technician comes in.
Sniffing Out Poisonous Air Pollution
Concerning detection methods, there are several types of CO detector technologies in use today. They are:
- Solid state
- Infrared light
In the first method, electromechanical, several electrodes are inserted into an electrolyte. As the electrolyte and probes join to generate a minute current, a reaction with the electrolyte ensues and an alarm sounds when CO is introduced into the environment.
Using this technology, it is suggested by one manufacturer that the electromechanical detector (module) be replaced every two years or so.
The solid-state method of CO detection relies on metal-oxide semiconductor technology. Using this technology, the semiconductor element is periodically heated, which causes it to react when CO is found in the environment. The degree of current change through the device reflects the amount of CO in the environment. The process itself requires a hefty amount of current to power the detector, often requiring the use of an auxiliary power supply.
The third method of CO detection is infrared (IR) light. This detection technology relies on the IR signature of CO when an IR light beam is passed through it. Detection occurs because CO exhibits a unique IR wavelength signature between 2 and 14 microns (wavelength).
For the sake of illustration, the system we will use to demonstrate the installation concerns associated with CO detection uses the IR method. In addition, our example system will summon help, once detection is verified, through an interconnected alarm system, and shut down the furnace that has likely caused it to occur.
Location Important to Installation
One of the most important aspects of CO detection is knowing where and where not to install detectors in the home. Because CO detection is so critical to life safety, placement is one of the most crucial parts of the installation. If one or more CO detectors are positioned incorrectly, they may not operate properly when an excessive CO situation occurs.
And just as important, improperly placed CO detectors can cause false alarms. This can cause a loss of confidence on the part of the occupants of the home and the fire authority whose job it is to respond to such calls for help. Thus, if an actual CO situation should take place, it is possible that no one will pay attention.
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