diff --git a/lambda/adc.c b/lambda/adc.c
index bfb56d4..526732a 100644
--- a/lambda/adc.c
+++ b/lambda/adc.c
@@ -38,7 +38,7 @@
 		sleep_mode();
 		overValue += ADC;
 	}
-	int16_t mV = (((overValue >> 2) * AREF_MV) >> 12) + ADC_OFFSET_MV;
+	int16_t mV = (((overValue >> 2) * AREF_MV) >> 12);
 
 	return mV;
 }
diff --git a/lambda/adc.h b/lambda/adc.h
index f0eb88b..15fb225 100644
--- a/lambda/adc.h
+++ b/lambda/adc.h
@@ -12,10 +12,9 @@
 #ifndef ADC_H_
 #define ADC_H_
 
-// TODO put in Makefile
 #define AREF_MV 5000
-#define ADC_OFFSET_MV 7
-#define TEMPO_OP_OFFSET_MV 454
+#define ADC_NONLIN_0 -8
+#define ADC_NONLIN_AREF 12
 
 /**
  * Sets up reference voltage and clock prescaler of the ADC and enables it.
@@ -24,8 +23,7 @@
 
 /**
  * Returns the voltage sampled at the given ADC input pin doing
- * 16x oversampling and taking in account the calibrated AREF and
- * ADC offset voltages.
+ * 16x oversampling and taking in account the calibrated AREF voltage.
  */
 uint16_t getVoltage(uint8_t pin);
 
diff --git a/lambda/command.c b/lambda/command.c
index 02c7ffa..fcd9d56 100644
--- a/lambda/command.c
+++ b/lambda/command.c
@@ -98,7 +98,8 @@
 	}
 	else if (simulation) {
 		Measurement meas = readMeas(fields, fieldCount);
-		if (getHeatingState() == HEATING_READY) {
+		if (getHeatingState() == HEATING_OFF ||
+				getHeatingState() == HEATING_READY) {
 			updateMeas(meas);
 		}
 		reason(meas);
diff --git a/lambda/lambda.c b/lambda/lambda.c
index f10f0e6..6c088e1 100644
--- a/lambda/lambda.c
+++ b/lambda/lambda.c
@@ -63,7 +63,8 @@
 			if (isLogging()) {
 				logMeas(meas);
 			}
-			if (getHeatingState() == HEATING_READY) {
+			if (getHeatingState() == HEATING_OFF ||
+					getHeatingState() == HEATING_READY) {
 				updateMeas(meas);
 			}
 			reason(meas);
diff --git a/lambda/rules.c b/lambda/rules.c
index 85a5d19..a370e14 100644
--- a/lambda/rules.c
+++ b/lambda/rules.c
@@ -96,6 +96,9 @@
 	}
 }
 
+/**
+ * Notifies that the heating is ready and sets the corresponding state.
+ */
 static void heatingReady(bool* const fired, int8_t const dir,
 		Measurement const meas) {
 	if (! isHeatingOn() || getHeatingState() == HEATING_READY) {
@@ -108,6 +111,10 @@
 	}
 }
 
+/**
+ * Notifies that the heating or its connection is faulty and sets the
+ * corresponding state.
+ */
 static void heatingFault(bool* const fired, int8_t const dir,
 		Measurement const meas) {
 	if (! isHeatingOn() || getHeatingState() == HEATING_FAULT) {
@@ -124,11 +131,23 @@
 }
 
 /**
- * Array of rules.
+ * Switches the heating off if it is still on after 3 hours and there does
+ * not seem to be a fire.
+ */
+static void heatingTimeout(bool* const fired, int8_t const dir,
+		Measurement const meas) {
+	if (isHeatingOn() && getTime() > SECOND * 10800UL && meas.tempI < 400) {
+		setHeatingOn(false);
+	}
+}
+
+// TODO what if fired up again without reset?
+// TODO what if reset during burndown?
+
+/**
+ * Rules applied to every nth averaged measurement
  */
 Rule rules[] = {
-		{false, heatingReady},
-		{false, heatingFault},
 		{false, airgate50},
 		{false, airgate25},
 		{false, airgateClose},
@@ -136,17 +155,32 @@
 		{false, fireOut}
 };
 
+/**
+ * Heater rules applied to each not averaged measured heater current value
+ */
+Rule heaterRules[] = {
+		{false, heatingReady},
+		{false, heatingFault},
+		{false, heatingTimeout}
+};
+
+
 // called about every second
 void reason(Measurement const meas) {
 
-	// TODO apply only heating* (not averaged) to every measurement
-	// and the other (averaged) rules only to every 10th measurement?
-	// if (age % 10 == 0) {
+	// rules applied to every 10th measurement
+	if (age % 10 == 0) {
 		size_t rulesSize = sizeof(rules) / sizeof(rules[0]);
 		for (size_t i = 0; i < rulesSize; i++) {
 			rules[i].cond(&(rules[i].fired), dir, meas);
 		}
-	// }
+	}
+
+	// rules applied to each measurement
+	size_t heaterRulesSize = sizeof(heaterRules) / sizeof(heaterRules[0]);
+	for (size_t i = 0; i < heaterRulesSize; i++) {
+		heaterRules[i].cond(&(heaterRules[i].fired), dir, meas);
+	}
 
 	age++;
 
@@ -184,4 +218,9 @@
 	for (size_t i = 0; i < rulesSize; i++) {
 		rules[i].fired = false;
 	}
+
+	size_t heaterRulesSize = sizeof(heaterRules) / sizeof(heaterRules[0]);
+	for (size_t i = 0; i < heaterRulesSize; i++) {
+		heaterRules[i].fired = false;
+	}
 }
diff --git a/lambda/sensors.c b/lambda/sensors.c
index ebaa14c..ed608d2 100644
--- a/lambda/sensors.c
+++ b/lambda/sensors.c
@@ -64,6 +64,14 @@
 };
 
 /**
+ * Table used to look up ADC measurement deviation due to non-linearity.
+ */
+static TableEntry const linADCTable[] = {
+	{ 0, ADC_NONLIN_0 },
+	{ AREF_MV, ADC_NONLIN_AREF }
+};
+
+/**
  * Variables holding averaged voltages*8.
  */
 static uint32_t lambdaVoltageAvg = 44 << 3; // Lambda 2.00
@@ -75,23 +83,25 @@
  * calculates an exponential moving average and displays the translated values.
  */
 Measurement measure(void) {
-	uint32_t tempIVoltage = getVoltage(ADC_TEMPI);
+	uint32_t tempIVoltage = linADC(getVoltage(ADC_TEMPI));
 	tempIVoltageAvg = tempIVoltage + tempIVoltageAvg -
 			((tempIVoltageAvg - 4) >> 3);
 
-	uint32_t tempOVoltage = getVoltage(ADC_TEMPO);
+	uint32_t tempOVoltage = linADC(getVoltage(ADC_TEMPO));
 	tempOVoltageAvg = tempOVoltage + tempOVoltageAvg -
 			((tempOVoltageAvg - 4) >> 3);
 
-	uint32_t lambdaVoltage = getVoltage(ADC_LAMBDA);
+	uint32_t lambdaVoltage = linADC(getVoltage(ADC_LAMBDA));
 	lambdaVoltageAvg = lambdaVoltage + lambdaVoltageAvg -
 			((lambdaVoltageAvg - 4) >> 3);
 
+	uint16_t heatingVoltage = linADC(getVoltage(ADC_HEATING));
+
 	Measurement meas;
 	meas.tempI = toTempI(tempIVoltageAvg >> 3);
 	meas.tempO = toTempO(tempOVoltageAvg >> 3);
 	meas.lambda = toLambda(lambdaVoltageAvg >> 3);
-	meas.current = toCurrent(getVoltage(ADC_HEATING));
+	meas.current = toCurrent(heatingVoltage);
 
 	return meas;
 }
@@ -158,6 +168,13 @@
 	return value;
 }
 
+int16_t linADC(uint16_t const mV) {
+	size_t size = sizeof(linADCTable) / sizeof(linADCTable[0]);
+	int16_t dev = lookupLinInter(mV, linADCTable, size);
+
+	return (int16_t)mV - dev;
+}
+
 char* toInfo(uint16_t const lambda) {
 	if (lambda > 190) {
 		return MSG_LEAN;
diff --git a/lambda/sensors.h b/lambda/sensors.h
index c3c497c..74ce199 100644
--- a/lambda/sensors.h
+++ b/lambda/sensors.h
@@ -93,6 +93,11 @@
 int16_t lookupLinInter(uint16_t mV, TableEntry const table[], size_t length);
 
 /**
+ * Returns the given ADC measurement with compensated ADC non-linearity.
+ */
+int16_t linADC(uint16_t mV);
+
+/**
  * Returns a descriptive term such as "Lean" for the given lambda value x1000.
  * For a wood fire, residual oxygen between 5% and 7% (lambda 1.3 and 1.5) is
  * a good value, below is rich and above is lean.