For COStar 24VC made by Quantum Group, we have an improved, 2nd generation COStar 24VC-E New Generation Main Board and Sensor Replacement kit (ETL certified). The life of Quantum COStar 24VC-E main board is 12 years. It will beep 60 days before the end of its life so that you have time to purchase this board and sensor replacement kit. Also this replacement kit is perfect for customers who own COSTAR® 24VC carbon monoxide ventilation control to retrofit. Since the first generation is obsolete we cannot offer a replacement sensor for these old 24VC, therefore we have developed a board and sensor replacement kit. It is much easier and more cost effective to replace a board and sensor than to replace the whole installation. COStar 24VC-E is approved by the City of Los Angeles.