By law the traps should be inspected at least once each day. Once caught the squirrel will be humanely dispatched, using an an air weapon.
This is an option I never use. internal baiting is just asking for trouble if the animal dies inside your home. External baiting unless done correctly can cause serious damage to the local wildlife population.
With an suitable air weapon, If done correctly is the most humane way to legally control troublesome squirrels.
Squirrels can quickly become a real nuisance when they are nesting in your home. The most common place they are found inside a property is in a roof space or behind fascia boards. Squirrels often gain access through a breach in the roof or under the eaves of the property. Cut back over hanging trees and repair damaged facia boards and secure loose tiles to prevent them from taking advantage of this and setting up home in your roof space. Even a small hole can be exploited by the squirrel. Once inside they cause damage to the insulation and have a habit of chewing on electrical cables, this can become a fire hazard.
David Etherington - your local pest control expert.