Wiring CO2 sensor

I have this carbon dioxide ($CO_2$) sensor:

http://wiring.org.co/learning/basics/airqualitymq135.html

My question is simple...
this sensor has left and right section. But what is left and what is right?
Is there a way to identify parts?

• Can we have a datasheet for the part? Not just a reference to the tutorial you got the images from please.
– Dean
Commented Jul 3, 2011 at 11:13
• Uhm... I don't have link for datasheet...
– elp
Commented Jul 3, 2011 at 11:17
• @Paska: You should do a little effort! Googling for "MQ135 datasheet" results in this document as the first hit. Commented Jul 3, 2011 at 16:00
• $CO_2$ is NOT Carbon Monoxide! $CO_2$ is Carbon Dioxide - which is it? Commented Jul 3, 2011 at 19:40
• @Matt - datasheet mentions $CO_2$ but not $CO$. fixed in the question. Commented Jul 8, 2011 at 8:44

Finding this datasheet online it says that A and B can be swapped and that H are the middle pins so that it can be in any orientation just make sure that H are the middle pins. Figure 2 is the one i'm referring to:

Well not going to datasheet, one can say from the image in your question, Just hold the sensor facing the pins towards your face, the pin assignment is same as per image (left B-H-B, right A-H-A)

and Dean has very simple answer :)

but my answer would help while using other Sensors along with their mechanical drawings

• Apparently there's no "A" and "B" marking, otherwise he wouldn't ask the question. The part is symmetrical, so if you rotate it over 180 degrees the pinning looks the same. You don't answer that. Commented Jul 3, 2011 at 15:56
• yes its symmetrical , i request you first view the manufactures datasheet and tell whether there's A and B Marking on sensor or not, Commented Jul 3, 2011 at 16:16
• dont jus rule out other's work who have done some reaserch and spent time.. Commented Jul 3, 2011 at 16:16
• Even all IC's (Integrated Circuits) the DIP one's have symmetrical physical pin arrangement, that doesn't mean you start pin1 from either of all four possibilities. Commented Jul 3, 2011 at 16:18
• The difference with DIP ICs is that they have a clear marking which side is pin 1. I've never heard anybody having trouble with the symmetry. This device doesn't have any marking, but without the datasheet the question how to identify A and B is justified. Commented Jul 3, 2011 at 16:48