Is your HVAC installation on the rooftop? NEMA 4-rated InnovairFlex™ watertight duct smoke detectors operate in the most challenging conditions without costly and bulky enclosures. Watertight InnovairFlex duct smoke detectors (D4120W conventional, DNRW intelligent) include a UV-resistant housing that provides protection against dirt, rain, and other water sources, so you can mount these detectors on HVAC equipment in harsh environments while saving on materials and labor.