Airlock doors are specialized doors designed to control the flow of air between two different environments, typically in a controlled or restricted manner. They are commonly used in various settings, such as spacecraft, submarines, cleanrooms, laboratories, and certain industrial facilities.
The primary purpose of an airlock door is to maintain the integrity of different environments by preventing the unwanted exchange of air, contaminants, or pressure between them. The door consists of two separate doors, usually referred to as the inner and outer doors, which cannot be opened simultaneously.
 
When someone or something needs to pass through the airlock, the process typically involves the following steps:
Initial door state: One door (usually the outer door) is closed, and the other door (usually the inner door) is open, effectively sealing off the two environments from each other.
Entry: The person or object enters the airlock through the open inner door.
Sealing: Once the person or object is inside the airlock, the inner door is closed, creating a sealed chamber.
Air pressure adjustment: The air pressure inside the sealed chamber is adjusted to match the pressure of the environment to which the person or object is transitioning. This step ensures a gradual change in pressure, minimizing the risk of injury or damage.
Exit: After the pressure adjustment is complete, the outer door can be opened, allowing the person or object to exit the airlock and enter the desired environment.
 
By implementing this two-door system and controlling the air pressure, airlock doors effectively prevent the uncontrolled flow of air, which could carry contaminants or disrupt the equilibrium between environments with different pressure levels. This mechanism helps maintain safety, cleanliness, and controlled conditions in various specialized settings