diff --git a/src/main/java/org/altbeacon/beacon/service/scanner/CycledLeScanner.java b/src/main/java/org/altbeacon/beacon/service/scanner/CycledLeScanner.java
index 4b6782339..4c640cd6f 100644
--- a/src/main/java/org/altbeacon/beacon/service/scanner/CycledLeScanner.java
+++ b/src/main/java/org/altbeacon/beacon/service/scanner/CycledLeScanner.java
@@ -15,6 +15,8 @@
 import android.os.HandlerThread;
 import android.os.Looper;
 import android.os.SystemClock;
+import android.support.annotation.MainThread;
+import android.support.annotation.NonNull;
 
 import org.altbeacon.beacon.BeaconManager;
 import org.altbeacon.beacon.logging.LogManager;
@@ -41,8 +43,30 @@ public abstract class CycledLeScanner {
 
     protected long mBetweenScanPeriod;
 
+    /**
+     * Main thread handle for scheduling scan cycle tasks.
+     * <p>
+     * Use this to schedule deferred tasks such as the following:
+     * <ul>
+     *     <li>{@link #scheduleScanCycleStop()}</li>
+     *     <li>{@link #scanLeDevice(Boolean) scanLeDevice(true)} from {@link #deferScanIfNeeded()}</li>
+     * </ul>
+     */
+    @NonNull
     protected final Handler mHandler = new Handler(Looper.getMainLooper());
+
+    /**
+     * Handler to background thread for interacting with the low-level Android BLE scanner.
+     * <p>
+     * Use this to queue any potentially long running BLE scanner actions such as starts and stops.
+     */
+    @NonNull
     protected final Handler mScanHandler;
+
+    /**
+     * Worker thread hosting the internal scanner message queue.
+     */
+    @NonNull
     private final HandlerThread mScanThread;
 
     protected final BluetoothCrashResolver mBluetoothCrashResolver;
@@ -177,6 +201,7 @@ public void destroy() {
         // So we stop the thread using the handler, so we make sure it happens after all other
         // waiting Runnables are finished.
         mHandler.post(new Runnable() {
+            @MainThread
             @Override
             public void run() {
                 LogManager.d(TAG, "Quitting scan thread");
@@ -270,6 +295,7 @@ protected void scheduleScanCycleStop() {
                 setWakeUpAlarm();
             }
             mHandler.postDelayed(new Runnable() {
+                @MainThread
                 @Override
                 public void run() {
                     scheduleScanCycleStop();
diff --git a/src/main/java/org/altbeacon/beacon/service/scanner/CycledLeScannerForJellyBeanMr2.java b/src/main/java/org/altbeacon/beacon/service/scanner/CycledLeScannerForJellyBeanMr2.java
index b38f7281c..42c6d6cbd 100644
--- a/src/main/java/org/altbeacon/beacon/service/scanner/CycledLeScannerForJellyBeanMr2.java
+++ b/src/main/java/org/altbeacon/beacon/service/scanner/CycledLeScannerForJellyBeanMr2.java
@@ -5,6 +5,8 @@
 import android.bluetooth.BluetoothDevice;
 import android.content.Context;
 import android.os.SystemClock;
+import android.support.annotation.MainThread;
+import android.support.annotation.WorkerThread;
 
 import org.altbeacon.beacon.logging.LogManager;
 import org.altbeacon.bluetooth.BluetoothCrashResolver;
@@ -36,6 +38,7 @@ protected boolean deferScanIfNeeded() {
                 setWakeUpAlarm();
             }
             mHandler.postDelayed(new Runnable() {
+                @MainThread
                 @Override
                 public void run() {
                     scanLeDevice(true);
@@ -65,6 +68,7 @@ private void postStartLeScan() {
         final BluetoothAdapter.LeScanCallback leScanCallback = getLeScanCallback();
         mScanHandler.removeCallbacksAndMessages(null);
         mScanHandler.post(new Runnable() {
+            @WorkerThread
             @Override
             public void run() {
                 try {
@@ -85,6 +89,7 @@ private void postStopLeScan() {
         final BluetoothAdapter.LeScanCallback leScanCallback = getLeScanCallback();
         mScanHandler.removeCallbacksAndMessages(null);
         mScanHandler.post(new Runnable() {
+            @WorkerThread
             @Override
             public void run() {
                 try {
diff --git a/src/main/java/org/altbeacon/beacon/service/scanner/CycledLeScannerForLollipop.java b/src/main/java/org/altbeacon/beacon/service/scanner/CycledLeScannerForLollipop.java
index 44a2fa9e0..fe44c5ac8 100644
--- a/src/main/java/org/altbeacon/beacon/service/scanner/CycledLeScannerForLollipop.java
+++ b/src/main/java/org/altbeacon/beacon/service/scanner/CycledLeScannerForLollipop.java
@@ -10,6 +10,8 @@
 import android.content.Context;
 import android.os.ParcelUuid;
 import android.os.SystemClock;
+import android.support.annotation.MainThread;
+import android.support.annotation.WorkerThread;
 
 import org.altbeacon.beacon.BeaconManager;
 import org.altbeacon.beacon.logging.LogManager;
@@ -134,6 +136,7 @@ protected boolean deferScanIfNeeded() {
                 setWakeUpAlarm();
             }
             mHandler.postDelayed(new Runnable() {
+                @MainThread
                 @Override
                 public void run() {
                     scanLeDevice(true);
@@ -190,6 +193,7 @@ private void postStartLeScan(final List<ScanFilter> filters, final ScanSettings
         final ScanCallback scanCallback = getNewLeScanCallback();
         mScanHandler.removeCallbacksAndMessages(null);
         mScanHandler.post(new Runnable() {
+            @WorkerThread
             @Override
             public void run() {
                 try {
@@ -220,6 +224,7 @@ private void postStopLeScan() {
         final ScanCallback scanCallback = getNewLeScanCallback();
         mScanHandler.removeCallbacksAndMessages(null);
         mScanHandler.post(new Runnable() {
+            @WorkerThread
             @Override
             public void run() {
                 try {