A nasal delivery device can include a nasal prong and an activation member. The nasal prong can have an opening at a top and bottom portion of the prong to allow for the passage of an aerosolized treatment agent through the nasal prong. The activation member can be positioned on the nasal delivery device at a location that is spaced apart from the subject's oral cavity when the nasal prong is received into the nostril of the subject. The activation member can detect a desired exhalation state of the subject and upon detection of the desired exhalation state, the activation member activates the delivery of the aerosolized treatment agent.