MQ gas sensors

I am planning to monitor the air quality by measuring the concentration of CO, LPG and Methane gases with MQ sensors that are linked below.

I came across the tutorial posted on Arduino website linked below.

Arduino Playground - MQGasSensors. Some parts on the tutorial are not clear, they are listed below.

  1. “The heater may not be connected directly to an output-pin of the Arduino, since it uses too much current for that.”
    Does it mean that I should not connect it to any of the digital pins ? Can I connect it to the 5 volts from the Arduino board ? or should I use external power supply for this.

  2. “A time of 12 or 24 hours is usually used for the burn-in time.”
    Do I need to supply 5 volts to the sensors for 12 hours?

  3. “In some special cases a specific burn-in is needed. See the datasheet if the sensor needs such a specific burn-in.”
    Do I need the specific burn in for MQ7, MQ6 and MQ4.

  4. Do I need a special library for the sensor, or can I only use the analogRead

Does it mean that I should not connect it to any of the digital pins ?

That is exactly what it means.

Can I connect it to the 5 volts from the Arduino board ? or should I use external power supply for this.

Read the data sheet for the sensor. How much current does the heater need? An external supply is certainly a better idea, if not mandatory.

  1. "A time of 12 or 24 hours is usually used for the burn-in time."
    Do I need to supply 5 volts to the sensors for 12 hours?

Wasn't that what it said?

  1. "In some special cases a specific burn-in is needed. See the datasheet if the sensor needs such a specific burn-in."
    Do I need the specific burn in for MQ7, MQ6 and MQ4.

Did you do as it said, and see the f**king data sheet? THAT is what an engineer does.

  1. Do I need a special library for the sensor, or can I only use the analogRead

Same answer as #3.