diff --git a/src/ZB.MOM.WW.ScadaBridge.DataConnectionLayer/Adapters/OpcUaAlarmMapper.cs b/src/ZB.MOM.WW.ScadaBridge.DataConnectionLayer/Adapters/OpcUaAlarmMapper.cs
new file mode 100644
index 00000000..12bfc238
--- /dev/null
+++ b/src/ZB.MOM.WW.ScadaBridge.DataConnectionLayer/Adapters/OpcUaAlarmMapper.cs
@@ -0,0 +1,52 @@
+using ZB.MOM.WW.ScadaBridge.Commons.Types.Alarms;
+using ZB.MOM.WW.ScadaBridge.Commons.Types.Enums;
+
+namespace ZB.MOM.WW.ScadaBridge.DataConnectionLayer.Adapters;
+
+/// <summary>
+/// Pure mapping helpers turning OPC UA Alarms &amp; Conditions event fields into the
+/// protocol-neutral <see cref="AlarmConditionState"/> / transition shape. Kept
+/// free of any OPC UA SDK types so it is unit-testable without a live server;
+/// the SDK field extraction lives in <c>RealOpcUaClient</c> and is exercised by
+/// the live smoke test (Task 28).
+/// </summary>
+public static class OpcUaAlarmMapper
+{
+    /// <summary>Clamps an OPC UA severity (1–1000, sometimes out of range) to the unified 0–1000 scale.</summary>
+    public static int NormalizeSeverity(int severity) => Math.Clamp(severity, 0, 1000);
+
+    /// <summary>Builds an <see cref="AlarmConditionState"/> from the orthogonal A&amp;C sub-states.</summary>
+    public static AlarmConditionState BuildCondition(
+        bool active, bool acked, bool? confirmed, AlarmShelveState shelve, bool suppressed, int severity) =>
+        new(Active: active, Acknowledged: acked, Confirmed: confirmed,
+            Shelve: shelve, Suppressed: suppressed, Severity: NormalizeSeverity(severity));
+
+    /// <summary>
+    /// Derives the transition kind from the change in active/acked sub-states.
+    /// Acknowledgement takes precedence over an active/inactive edge when both
+    /// change in the same event; an unchanged event is reported as a StateChange.
+    /// </summary>
+    public static AlarmTransitionKind DeriveKind(bool prevAcked, bool nowAcked, bool prevActive, bool nowActive)
+    {
+        if (!prevAcked && nowAcked)
+            return AlarmTransitionKind.Acknowledge;
+        if (!prevActive && nowActive)
+            return AlarmTransitionKind.Raise;
+        if (prevActive && !nowActive)
+            return AlarmTransitionKind.Clear;
+        if (prevActive && nowActive)
+            return AlarmTransitionKind.Retrigger;
+        return AlarmTransitionKind.StateChange;
+    }
+
+    /// <summary>Maps the OPC UA ShelvingState current-state node name to the shelve enum.</summary>
+    public static AlarmShelveState MapShelve(string? shelvingStateName) => shelvingStateName switch
+    {
+        "OneShotShelved" => AlarmShelveState.OneShotShelved,
+        "TimedShelved" => AlarmShelveState.TimedShelved,
+        // OPC UA does not expose a distinct "permanent" shelve; treat any other
+        // shelved name as one-shot and "Unshelved"/null as unshelved.
+        null or "Unshelved" => AlarmShelveState.Unshelved,
+        _ => AlarmShelveState.OneShotShelved
+    };
+}
diff --git a/tests/ZB.MOM.WW.ScadaBridge.DataConnectionLayer.Tests/OpcUaAlarmMapperTests.cs b/tests/ZB.MOM.WW.ScadaBridge.DataConnectionLayer.Tests/OpcUaAlarmMapperTests.cs
new file mode 100644
index 00000000..df034bce
--- /dev/null
+++ b/tests/ZB.MOM.WW.ScadaBridge.DataConnectionLayer.Tests/OpcUaAlarmMapperTests.cs
@@ -0,0 +1,58 @@
+using ZB.MOM.WW.ScadaBridge.Commons.Types.Enums;
+using ZB.MOM.WW.ScadaBridge.DataConnectionLayer.Adapters;
+
+namespace ZB.MOM.WW.ScadaBridge.DataConnectionLayer.Tests;
+
+/// <summary>Task-11: pure OPC UA A&C field → AlarmConditionState/transition mapping.</summary>
+public class OpcUaAlarmMapperTests
+{
+    [Fact]
+    public void NormalizeSeverity_ClampsTo0_1000()
+    {
+        Assert.Equal(1000, OpcUaAlarmMapper.NormalizeSeverity(5000));
+        Assert.Equal(0, OpcUaAlarmMapper.NormalizeSeverity(-1));
+        Assert.Equal(500, OpcUaAlarmMapper.NormalizeSeverity(500));
+    }
+
+    [Fact]
+    public void BuildCondition_ActiveUnacked()
+    {
+        var c = OpcUaAlarmMapper.BuildCondition(active: true, acked: false, confirmed: null,
+            shelve: AlarmShelveState.Unshelved, suppressed: false, severity: 700);
+        Assert.True(c.Active);
+        Assert.False(c.Acknowledged);
+        Assert.Equal(700, c.Severity);
+        Assert.Equal(AlarmShelveState.Unshelved, c.Shelve);
+    }
+
+    [Fact]
+    public void DeriveKind_AckEdge_YieldsAcknowledge()
+    {
+        Assert.Equal(AlarmTransitionKind.Acknowledge,
+            OpcUaAlarmMapper.DeriveKind(prevAcked: false, nowAcked: true, prevActive: true, nowActive: true));
+    }
+
+    [Fact]
+    public void DeriveKind_ActiveEdge_YieldsRaise()
+    {
+        Assert.Equal(AlarmTransitionKind.Raise,
+            OpcUaAlarmMapper.DeriveKind(prevAcked: true, nowAcked: true, prevActive: false, nowActive: true));
+    }
+
+    [Fact]
+    public void DeriveKind_InactiveEdge_YieldsClear()
+    {
+        Assert.Equal(AlarmTransitionKind.Clear,
+            OpcUaAlarmMapper.DeriveKind(prevAcked: true, nowAcked: true, prevActive: true, nowActive: false));
+    }
+
+    [Theory]
+    [InlineData("OneShotShelved", AlarmShelveState.OneShotShelved)]
+    [InlineData("TimedShelved", AlarmShelveState.TimedShelved)]
+    [InlineData("Unshelved", AlarmShelveState.Unshelved)]
+    [InlineData(null, AlarmShelveState.Unshelved)]
+    public void MapShelve_MapsCurrentStateName(string? name, AlarmShelveState expected)
+    {
+        Assert.Equal(expected, OpcUaAlarmMapper.MapShelve(name));
+    }
+}