Patented CostarÂ® CO-detecting ventilation fan controller monitors the CO level in the surrounding air and activates the ventilation system when the level exceeds recommended limits (dependent on local regulations). A single controller monitors up to 10,000 sq ft. Multiple controller installations are made by series connection of the desired number of units; no central panel is needed, the company says. Other features include status lights on the front panel and fail-safe circuit design. The unit comes in 24- and 120-vac models. Tracy Leigh Enterprises, P.O. Box 831, Brodheadsville, PA 18322; 877-570-6961; 570-992-5026.