Table of Contents
- Why LPG Leak Detection Matters in India
- MQ6 vs MQ2 for LPG
- Components
- Arduino Detection Code
- Automation: Fan and Valve
- LPG Safety Guidelines India
- FAQ
Why LPG Leak Detection Matters in India
India uses over 300 million LPG (Liquified Petroleum Gas) cylinder connections for domestic cooking. LPG is heavier than air and settles to the floor in enclosed spaces. Concentrations above 2.15% in air are explosive when ignited. LPG leak accidents cause hundreds of deaths and thousands of injuries annually in India, typically from delayed detection of slow cylinder valve leaks or faulty regulator O-rings. A gas leak alarm with MQ6 sensor costs Rs 200-500 to build and provides lifesaving protection.
MQ6 vs MQ2 for LPG
Both sensors detect LPG, but they have different sensitivities:
- MQ2 (Rs 40-80): Sensitive to LPG, propane, methane, smoke, alcohol, hydrogen. Suitable for general gas leak detection. Less selective.
- MQ6 (Rs 60-100): Optimised for LPG and butane/propane gases specifically. Lower cross-sensitivity to cooking smoke, alcohol, and hydrogen. Better for dedicated LPG kitchen alarms in Indian homes where cooking also generates smoke.
For a dedicated LPG alarm in an Indian kitchen, MQ6 is the better choice as it produces fewer false alarms from cooking. For a combined smoke/gas alarm, MQ2 covers more scenarios.
Components
- Arduino Uno or ESP8266 NodeMCU
- MQ6 LPG gas sensor (Rs 60-100)
- SIM800L GSM module (Rs 200-350) for SMS alert
- 5V relay module x2 (for exhaust fan and solenoid gas valve)
- Loud buzzer or siren module (Rs 15-80)
- 12V solenoid gas safety valve (Rs 800-2,000 – optional but recommended)
- 230V exhaust fan (existing kitchen exhaust)
Arduino Detection Code
#define MQ6_PIN A0
#define BUZZER 8
#define FAN_RELAY 9
#define VALVE_RELAY 10
int cleanAir=0, alarmThreshold=0;
void setup(){
Serial.begin(9600);
Serial.println("Preheating MQ6 sensor (20s)...");
delay(20000);
long sum=0;
for(int i=0;i<100;i++){ sum+=analogRead(MQ6_PIN); delay(10); }
cleanAir=sum/100;
alarmThreshold=cleanAir*1.8; // 80% above clean air = LPG present
Serial.print("Clean air baseline: "); Serial.println(cleanAir);
}
void loop(){
int reading=analogRead(MQ6_PIN);
if(reading>alarmThreshold){
tone(BUZZER,2400);
digitalWrite(FAN_RELAY,HIGH); // turn on exhaust fan
digitalWrite(VALVE_RELAY,LOW); // close solenoid valve (NC valve)
// sendSMS("+91XXXXXXXXXX","GAS LEAK DETECTED IN KITCHEN!");
} else {
noTone(BUZZER);
if(reading<cleanAir*1.2){
digitalWrite(FAN_RELAY,LOW);
digitalWrite(VALVE_RELAY,HIGH);
}
}
delay(200);
}Automation: Fan and Valve
On gas detection, two safety actions should trigger automatically:
- Turn on exhaust fan: Connect the kitchen exhaust fan to a 230V relay (rated for 230V/10A). When gas is detected, activate the fan to ventilate the kitchen before concentration reaches explosive levels.
- Close solenoid gas valve: A 12V normally-closed solenoid valve installed on the gas supply line automatically cuts off gas flow when de-energised. This stops new gas from entering even if the alarm is not heard. Cost: Rs 800-2,000 for a 1/2-inch 12V NC solenoid valve from plumbing suppliers.
Only reset the solenoid valve (allow gas flow again) after confirming the leak is resolved and the MQ6 reading returns to baseline.
LPG Safety Guidelines India
- Mount MQ6 sensor at 30cm above floor level (LPG is heavier than air)
- Never mount near cooking flame or directly above the stove
- Check for LPG leaks by smell, not by lighting a match
- In India, check cylinder valve and regulator O-ring annually (BIS IS 9062 standard O-ring should be replaced annually)
- Keep cylinder in ventilated area – never inside a closed cabinet
- In case of leak detected: do not turn on/off any electrical switch (spark hazard), open all windows, evacuate, call LPG distributor
Frequently Asked Questions
What concentration of LPG is dangerous?
LPG (predominantly propane and butane) lower explosive limit (LEL) is 2.15% in air. At 10% of LEL (0.215% or 2,150 ppm), many sensors trigger a first-level alert. At 25% of LEL (0.54%), most professional detectors trigger an alarm. For home use, set your MQ6 alarm to trigger at about 40-50% of LEL for adequate warning time before dangerous concentration is reached.
My MQ6 alarm keeps triggering when I cook – how do I fix it?
MQ6 is much more selective for LPG than MQ2, but high-heat cooking (deep frying, tempering with ghee) still produces some aldehydes and ketones that cross-sensitise. Raise the detection threshold slightly (multiply baseline by 2.0 instead of 1.8) and add a 5-second sustained reading filter. Also ensure the sensor is not directly above the stove – mount it 30cm above floor, away from the cooking area but within 1m of the gas cylinder connection point.
Can I install this system in a piped gas (PNG) kitchen?
Yes – PNG (Piped Natural Gas) used in cities like Mumbai, Delhi, Pune, Hyderabad is primarily methane. MQ6 is less sensitive to methane than LPG but still detects it at elevated concentrations. For PNG, the MQ4 sensor (optimised for methane/natural gas) is a better choice. MQ2 works for both LPG and PNG. Install at ceiling level for PNG (methane is lighter than air and rises to ceiling).
Is a solenoid gas valve legal to install on an Indian LPG cylinder?
Yes – 12V solenoid valves installed at the point of use (after the regulator, on the gas supply tube to the stove) are legal and recommended for safety. They do not affect the BIS-certified cylinder pressure regulator. Choose a valve rated for LPG (not water or air) with appropriate pressure rating. Some Indian insurance policies actually offer discounts for LPG safety valve installation.
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