A covered chamberless particulate detector includes a chamberless detector configured to produce a signal when particulate sensing events occur; one or more optical emitters disposed on the chamberless detector, configured to emit one or more emitting cones of light; one or more optical sensors disposed on the chamberless detector, defining one or more receiving cones; and a protective cover on the chamberless detector defining an inside region and an outside region. Each of the one or more optical sensors is configured to detect occurrence of particulate sensing events. The protective cover includes a material having one or more optical properties of transmission, reflection, and absorption; and at least of these optical properties has a bandwidth.