A compact diffuser integrates an atomizer and droplet separator into a surrounding sleeve, threadable to a bottle neck as an assembly. The assembly fits into a base, housing a motor and air pump, sealing the sleeve to a silo in the housing. Controls set time span of intermittent operation, intervening delay, and volumetric flow rate. The assembly pops into (and out of) the top end of a silo in the base, registering (aligning) circumferentially and axially to seal an air path from the pump to the atomizer. Access for applying force to the bottom of the assembly facilitates popping out the assembly when empty, or to simply change scent by changing out the assembly. Entire assemblies may be stored to simplify exchange and reduce chances for spills from reservoirs.