Current SIR Sensor Technology

The SIR sensor housing is shown in Figure 1. The housing protects the sensing elements from physical damage and harm. A filter (getter) and retainer clip hold the sensing elements in place and prevent dust, smoke particles, liquid water, and other chemicals from entering the sensor chamber. The SIR sensing elements are held in optical alignment by the sensor housing placed between an infrared light emitting diode (LED) and a photodiode.

Figure 2 shows the view of the optical path of LED and photodiode through the sensing disks. The infrared LED pulses every 30 second to measure the transmission of the sensor disks. The photodiode reads the amount of sensor optical change at 940 nm, which is the infrared wavelength of the LED. This rate of change of the response to carbon monoxide is proportional to the carbon monoxide concentration. The microprocessor determines when the alarm should sound based on the sensor response measurements.

Only COSTAR® carbon monoxide alarm technology gives reliable protection without false alarms. Liquid electrochemical CO sensors and metal oxide semiconductor technology — used in most competitors’ detectors — are sensitive to many common household gases, particularly from disinfectants, cleaning products and air fresheners. Their frequent false alarms can lead people to ignore valid alerts, with fatal results.

COSTAR® detectors, on the other hand, react only to the presence of carbon monoxide gas, and will not be affected in normal operation to other gasses found in a typical household during its 6 year life.