diff --git a/Content.Server/Atmos/Monitor/Components/AirAlarmComponent.cs b/Content.Server/Atmos/Monitor/Components/AirAlarmComponent.cs
index 3d95b626df..67e18b8f9e 100644
--- a/Content.Server/Atmos/Monitor/Components/AirAlarmComponent.cs
+++ b/Content.Server/Atmos/Monitor/Components/AirAlarmComponent.cs
@@ -15,10 +15,10 @@ public sealed class AirAlarmComponent : Component
 
     [ViewVariables] public AirAlarmTab CurrentTab { get; set; }
 
-    public Dictionary<string, IAtmosDeviceData> DeviceData = new();
-    public Dictionary<string, GasVentPumpData> VentData = new();
-    public Dictionary<string, GasVentScrubberData> ScrubberData = new();
-    public Dictionary<string, AtmosSensorData> SensorData = new();
+    public readonly HashSet<string> KnownDevices = new();
+    public readonly Dictionary<string, GasVentPumpData> VentData = new();
+    public readonly Dictionary<string, GasVentScrubberData> ScrubberData = new();
+    public readonly Dictionary<string, AtmosSensorData> SensorData = new();
 
     public HashSet<NetUserId> ActivePlayers = new();
 
diff --git a/Content.Server/Atmos/Monitor/Systems/AirAlarmSystem.cs b/Content.Server/Atmos/Monitor/Systems/AirAlarmSystem.cs
index f204ce1882..4fc027d374 100644
--- a/Content.Server/Atmos/Monitor/Systems/AirAlarmSystem.cs
+++ b/Content.Server/Atmos/Monitor/Systems/AirAlarmSystem.cs
@@ -182,6 +182,7 @@ public sealed class AirAlarmSystem : EntitySystem
         {
             ForceCloseAllInterfaces(uid);
             component.CurrentModeUpdater = null;
+            component.KnownDevices.Clear();
             component.ScrubberData.Clear();
             component.SensorData.Clear();
             component.VentData.Clear();
@@ -232,6 +233,7 @@ public sealed class AirAlarmSystem : EntitySystem
     {
         if (AccessCheck(uid, args.Session.AttachedEntity, component))
         {
+            component.KnownDevices.Clear();
             component.VentData.Clear();
             component.ScrubberData.Clear();
             component.SensorData.Clear();
@@ -384,8 +386,6 @@ public sealed class AirAlarmSystem : EntitySystem
 
                 // Save into component.
                 // Sync data to interface.
-                // _airAlarmDataSystem.UpdateDeviceData(uid, args.SenderAddress, data);
-                //
                 switch (data)
                 {
                     case GasVentPumpData ventData:
@@ -402,6 +402,8 @@ public sealed class AirAlarmSystem : EntitySystem
                         break;
                 }
 
+                controller.KnownDevices.Add(args.SenderAddress);
+
                 UpdateUI(uid, controller);
 
                 return;
@@ -500,7 +502,7 @@ public sealed class AirAlarmSystem : EntitySystem
             }
         }
 
-        var deviceCount = alarm.VentData.Count + alarm.ScrubberData.Count + alarm.SensorData.Count;
+        var deviceCount = alarm.KnownDevices.Count;
 
         if (!_atmosAlarmable.TryGetHighestAlert(uid, out var highestAlarm))
         {