This document describes a breathalyzer door lock system that uses a PIC microcontroller. It checks the breath alcohol content (BAC) level using a gas sensor, and prevents the door from opening if the person is intoxicated. It also includes an keypad for administrative access. The system is intended to prevent drunken driving by not allowing intoxicated people to leave in a vehicle. It provides details on the components, including the microcontroller, gas sensor, keypad, LCD display, DC motor and more. Circuit diagrams and block diagrams are also included to explain how it works.