Tested with:

/************************************************************************************
EasyAPI - Documentation: http://psteamcommunity.yuanyoumao.com/sharedfiles/filedetails/?id=381043
*************************************************************************************/
// This script was made for the LKS_Hydros but can be applied to similar ships
// That means just one group for outer doors, one for inner doors, and one for all the doors
// Feel free to rename the groups accordingly.
//

public static string AIRLOCK_DOORS = "HY 1- Doors"; // your doors group
public static string AIRLOCK_OUTER_DOORS = "HY 1- Doors (Outer)"; // your outer doors group
public static string AIRLOCK_INNER_DOORS = "HY 1- Doors (Inner)"; // your inner doors group
public static bool AIRLOCK_AUTOCLOSE = true; // set it to true if you want the door closing automaticaly after a delay
public static long AIRLOCK_AUTOCLOSEDELAY = 3 * EasyAPI.Seconds; // autoclose delay set to 3 seconds, change it if you want

public class Example : EasyAPI
{
public Example(IMyGridTerminalSystem grid, IMyProgrammableBlock me, Action<string> echo, TimeSpan elapsedTime) : base(grid, me, echo, elapsedTime)
{
// if an outer door is open we close all the other (outer/inner) doors
Blocks.InGroupsNamed(AIRLOCK_OUTER_DOORS).AddEvent(
delegate(EasyBlock thisdoor)
{
return thisdoor.Open();
},
delegate(EasyBlock thisdoor)
{
Blocks.InGroupsNamed(AIRLOCK_DOORS).Minus(thisdoor).ApplyAction("Open_Off");
if(AIRLOCK_AUTOCLOSE) // autoclose the outer door that was open, if any
{
In(AIRLOCK_AUTOCLOSEDELAY, delegate()
{
thisdoor.ApplyAction("Open_Off");
});
}

return true;
},
true
);

// if an inner door is open we close all the other (outer/inner) doors
Blocks.InGroupsNamed(AIRLOCK_INNER_DOORS).AddEvent(
delegate(EasyBlock thisdoor)
{
return thisdoor.Open();
},
delegate(EasyBlock thisdoor)
{
Blocks.InGroupsNamed(AIRLOCK_DOORS).Minus(thisdoor).ApplyAction("Open_Off");
if(AIRLOCK_AUTOCLOSE) // autoclose the inner door that was open, if any
{
In(AIRLOCK_AUTOCLOSEDELAY, delegate()
{
thisdoor.ApplyAction("Open_Off");
});
}

return true;
},
true
);
}
}

/*********************************************/
/*** Advanced users only beyond this point ***/
/*********************************************/
...

As you can see the door you just opened can be also automaticaly closed behind you after a delay. Just change the AIRLOCK_AUTOCLOSE and AIRLOCK_AUTOCLOSEDELAY the way you want.

Enjoy,
LKS

Of course this is just an example. Maybe you do not want to close all the outer doors when opening an inner door (because outer doors have their own airlock system for example). Up to you to adapt this code to your needs ;)

LKS

Here's another spin at the airlock doors script. It is based on the example door close script on EasyAPI GitHub page.

By default it will auto close any door after 2-3sec.
If you name two or more doors with exactly same name this script will make sure only one door of the same name can be open at one time by turning off the other(s).

In my example this is the same function for either inner/outer doors ... of course you can simplify the code and apply it to the whole group AIRLOCK_DOORS but I decided to split inner/outer doors in case of you want to add some functions to them (activate inner turrets, trigger an alarm, etc)

This is your code, not mine ;)
LKS