A can of Tri Die will be fine to sit in your mailbox until you get home. You would just want to bring it to a cool temperature stable area once you retrieve it and keep it stored in that cool area throughout the duration of the cans use.
PT Tri-Die Pressurized Dust Insecticide is labeled for spo treating localized termite infestations as directed on the product label.
You should not apply PT Tri-Die Pressurized Dust Insecticide or other insecticides directly into an air vent. You could potentially apply this around the edges around the vent cover to treat into a wall void; however, you should not apply insecticides directly into any air vents.
