Laboratory methodology is described for measuring relative emission rates of behavior-controlling chemicals (e.g., pheromones), particularly from slow-release formulations intended for such uses as permeation of air with pheromone to disorient insects seeking mates or attraction of insects to traps for detection or suppression. An apparatus was constructed to age formulations for long periods of time by passing air at a fixed temperature over planchets containing microencapsulated pheromone. Another apparatus was devised to measure the relative emission rates of pheromone from samples after suitable intervals of aging while air at 100 ml/min passed over the samples. These procedures, used in combination with field testing, may expedite the acquisition of data needed to develop suitable formulations of pheromone for control of pest insects.