diff --git a/aqimon/read/mock.py b/aqimon/read/mock.py
index 5c4f841..9ad818d 100644
--- a/aqimon/read/mock.py
+++ b/aqimon/read/mock.py
@@ -11,11 +11,12 @@
 class MockReader:
     """Mock reader class."""
 
-    def __init__(self, fake_sleep_secs=5, raise_error_odds=50):
+    def __init__(self, fake_sleep_secs=5, raise_error_odds=50, warm_up_secs=5):
         """Create a mock reader."""
         self.state = ReaderState(ReaderStatus.IDLE, None)
         self.fake_sleep_secs = fake_sleep_secs
         self.raise_error_odds = raise_error_odds
+        self.warm_up_secs = warm_up_secs
 
     async def read(self) -> AqiRead:
         """Read from the 'device'.
@@ -25,6 +26,8 @@ async def read(self) -> AqiRead:
         Also, randomly fails some percentage of the time.
         """
         try:
+            self.state = ReaderState(ReaderStatus.WARM_UP, None)
+            await asyncio.sleep(self.warm_up_secs)
             self.state = ReaderState(ReaderStatus.READING, None)
             raise_error_roll = random.randint(0, 100)
             if raise_error_roll < self.raise_error_odds:
diff --git a/aqimon/static/images/loading.gif b/aqimon/static/images/loading.gif
index be8a5be..d5d42eb 100644
Binary files a/aqimon/static/images/loading.gif and b/aqimon/static/images/loading.gif differ
diff --git a/aqimon/static/images/warmingup.gif b/aqimon/static/images/warmingup.gif
new file mode 100644
index 0000000..8ac68d8
Binary files /dev/null and b/aqimon/static/images/warmingup.gif differ
diff --git a/elm/src/DeviceStatus.elm b/elm/src/DeviceStatus.elm
index 808e712..4dae794 100644
--- a/elm/src/DeviceStatus.elm
+++ b/elm/src/DeviceStatus.elm
@@ -61,7 +61,7 @@ deviceStatusImage deviceStatus =
             "/static/images/loading.gif"
 
         WarmingUp ->
-            "/static/images/loading.gif"
+            "/static/images/warmingup.gif"
 
         Idle ->
             "/static/images/idle.png"