Why CO Detector Choice Is Critical

Increasingly, states and local jurisdictions are mandating the installation of carbon monoxide (CO) detectors. Alarm professionals therefore must not only comply with the industry’s most recent product standards, but understand the differences among various new requirements.

The carbon monoxide (CO) detection market has continued to experience significant growth the past few years, providing installing security contractors with added revenue opportunities. Namely, this marketplace expansion is being driven by legislation requiring the installation of CO detectors in single- and two-family dwellings, and commercial occupancies such as hotels, child and adult daycare facilities, and university dormitories. Currently, there are 29 states along with many major municipalities that have enacted CO regulations.

As security and fire/life-safety professionals evaluate which CO detector to purchase or install, the key is to look for a product that’s not only listed for the intended use, but also has features that comply with the industry’s most recent product standards.

Installing security contractors will need to become educated on the differences between American National Standards Institute (ANSI) and Underwriters Laboratories (UL) standards ANSI/UL 2034 and ANSI/UL 2075, plus be aware of the new requirements of the third edition of ANSI/UL 2075 that became effective in late 2009.

ANSI/UL 2034, Single and Multiple Station Carbon Monoxide Alarms, is the product standard for self-contained CO alarms. These alarms are not designed to be connected to an alarm control panel. The primary operating power for these devices is derived from a battery, a plug-in that uses a two- or three-prong attachment plug or is wired into the dwelling’s AC power line with secondary power backup.

ANSI/UL 2075, Gas and Vapor Detectors and Sensors, is the product standard for CO detectors that are intended to be system-connected to an alarm control panel. This is typically done via conductors, extending from the detector to the control panel or low-power radio frequency signal.

Even though there are two standards for CO detection devices, both have the same alarm thresholds. ANSI/UL 2075 requires detectors to operate within the sensitivity parameters defined in ANSI/UL 2034. The alarm thresholds, set by CO concentration measured in parts per million (ppm), are: no alarm below 30 ppm until after 30 days; 70 ppm for one to four hours (but not less than one hour); 150 ppm for 10 to 50 minutes; 400 ppm for four to 15 minutes.

Because the current gas sensing technologies on the market — biomimetic, metal oxide semiconductor (MOS) and electrochemical — all have a limited life, it is imperative the gas sensing element be supervised to ensure continuous operation. The new requirements of the third edition of ANSI/UL 2075 address this issue by mandating critical life-safety supervision features that will prevent a failed detector from going undetected.

These new requirements are fundamental concepts of all life-safety products, such as fire alarm system devices and central station service.

The new ANSI/UL 2075 requires the detector to electrically supervise the gas sensing element so when the sensor reaches its end-of-life (EOL), the detector will send a trouble signal to the control panel. This new electrical supervision requirement of the CO sensing element is vital for safe and effective performance of the detector.

To be compliant with ANSI/UL 2075, life-safety professionals should ensure their chosen system-connected CO detectors incorporate an integral trouble relay that sends a trouble signal to the control panel when the CO sensor has reached its EOL. This can be a point of confusion for professionals, because smoke detectors generally do not have limited-life components.

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