user3425: What does the MQ-2 sensor detect?
I know it detects concentrations of flammable gas. But does it detect smoke from fires too?
What about smoke from cigarettes, and other things?

user3219: Simple answer is no. 
There are about 10 similar sensors, each detect specific kind of chemicals 

3425: <p>What does the <a href="http://linksprite.com/wiki/index.php5?title=MQ2_Smoke_Detector_Shield_for_Arduino" rel="nofollow">MQ-2</a> sensor detect?</p>

<p>I know it detects concentrations of flammable gas. But does it detect smoke from fires too?
What about smoke from cigarettes, and other things?</p>
 3219: <p>Simple answer is no. </p>

<p>There are about 10 similar sensors, each detect specific kind of chemicals </p>
