diff --git a/lib/timer.js b/lib/timer.js
index c65a34c..2e655d7 100644
--- a/lib/timer.js
+++ b/lib/timer.js
@@ -49,7 +49,7 @@ class Timer extends Component {
 
   componentWillReceiveProps(newProps) {
 
-    if(newProps.start) {
+    if (newProps.start) {
       this.start();
     } else {
       this.stop();
@@ -59,7 +59,16 @@ class Timer extends Component {
     }
   }
 
+  componentWillUnmount() {
+    this.stop()
+  }
+
   start() {
+    if (this.interval) {
+      // already running, no need to re-start
+      return;
+    }
+
     const handleFinish = this.props.handleFinish ? this.props.handleFinish : () => alert("Timer Finished");
     const endTime = new Date().getTime() + this.state.remainingTime;
     this.interval = setInterval(() => {
@@ -71,11 +80,12 @@ class Timer extends Component {
         return;
       }
       this.setState({remainingTime: remaining});
-    }, 1);
+    }, 100);
   }
 
   stop() {
     clearInterval(this.interval);
+    this.interval = null;
   }
 
   reset(newDuration) {
diff --git a/package.json b/package.json
index 84fd297..8276d3b 100644
--- a/package.json
+++ b/package.json
@@ -1,6 +1,6 @@
 {
   "name": "react-native-stopwatch-timer",
-  "version": "0.0.21",
+  "version": "0.0.22",
   "description": "A stopwatch/timer component for React Native.",
   "repository": {
     "type": "git",
@@ -17,4 +17,4 @@
   "dependencies": {
     "prop-types": "^15.7.2"
   }
-}
+}
\ No newline at end of file