Is it permissible to engage in personal matters or attend to personal needs from home during work hours, given the ability to immediately commence any urgent tasks?

The employee is a private contractor, and his services are owned by his employer during working hours. Therefore, it is not permissible for him to work for himself or for others except with the explicit or customary permission of his employer. The ruling does not differ in this regard, whether the work is performed from the workplace or from home, and customary permission takes the place of explicit permission.