diff --git a/elements/linechart.js b/elements/linechart.js
index 123967d..caed171 100644
--- a/elements/linechart.js
+++ b/elements/linechart.js
@@ -27,6 +27,7 @@ class LineChart extends Component {
     shape: props.string,
     width: props.number,
     height: props.number,
+    references: props.string,
   };
 
   connected() {
@@ -78,7 +79,7 @@ class LineChart extends Component {
     injectCss(root);
   }
 
-  render({ data, shape, width, height }) {
+  render({ data, shape, width, height, references }) {
     const el = document.createElement('div');
     if (!data || !data.length) {
       // No data yet
@@ -105,6 +106,24 @@ class LineChart extends Component {
       }
       return res;
     });
+
+    const shapes = references.split(' ').map((spec) => {
+      const s = spec.split(',');
+      const res = {
+        type: 'line',
+        xref: 'paper', // x relative to [0,1] "paper" axis
+        yref: 'y',
+        x0: 0,
+        x1: 1,
+        y0: s[0],
+        y1: s[0],
+        line: {
+          color: s[1],
+          width: 2.5,
+        },
+      };
+      return res;
+    });
     const layout = {
       autosize: false,
       width: graphWidth,
@@ -143,6 +162,7 @@ class LineChart extends Component {
         r: 0,
       },
       showlegend: showLegend,
+      shapes,
       paper_bgcolor: 'transparent',
       plot_bgcolor: 'transparent',
     };
diff --git a/life-support/index.html b/life-support/index.html
index 042e44b..53f7ffc 100644
--- a/life-support/index.html
+++ b/life-support/index.html
@@ -94,11 +94,11 @@
     <main>
       <section id="climate-pm10">
         <h2>PM<sub>10</sub></h2>
-        <cbase-linechart timeseries="clima.pm10.mainhall clima.pm10.arboretum" width="34" height="40"></cbase-linechart>
+        <cbase-linechart timeseries="clima.pm10.mainhall clima.pm10.arboretum" width="34" height="40" references="50,yellow 150,red"></cbase-linechart>
       </section>
       <section id="climate-pm25">
         <h2>PM<sub>2.5</sub></h2>
-        <cbase-linechart timeseries="clima.pm25.mainhall clima.pm25.arboretum" width="34" height="40"></cbase-linechart>
+        <cbase-linechart timeseries="clima.pm25.mainhall clima.pm25.arboretum" width="34" height="40" references="25,yellow 35,red"></cbase-linechart>
       </section>
       <section id="drinks-status">
         <cbase-currentstate id="bar-status" timeseries="bar.open" interval="10">bar</cbase-currentstate>