9pcs/Lot Gas Detection Sensor Module MQ-2 MQ-3 MQ-4 MQ-5 MQ-6 MQ-7 MQ-8 MQ-9 MQ-135 Sensor Module Gas Sensor Starter Kit for Arduino Raspberry Pi (9PCS/Lot)

Detects my farts... hehe. I was using these to make a multi gas sensor array. Never finished it. Here was my plan... each sensor responds to a set of gases on curves. It would calculate the Ro of each and then ppm of each gas. Take the stddev of each gas one by one. The lowest stddev is probably gas. Easy. Lol

They were all individually bagged in static-free sealed packs which is very nice, I haven't yet tested them as far as using them with a microcontroller with a sketch running but I did test to see if they powered up and they all seem to work . I am working on some code right now to integrate them into a project , once that's done I will update this review and let everyone know more on how well they actually work. I suspect they will work just fine! All in all I'm very satisfied so far with the price and perceived quality as of now.

Works great for alcohol and gas detection. Not so well for smoke.

They all say mq sensor but only three had stickers identifying which sensor they are.

Is it really an mq-2? Cant tell....... it has the same markins as all the other mq sensors i bought, not sure what it is to be honest.

It's really unclear if these are carbon monoxide sensors or carbon dioxide sensors. I couldn't find any straight forward documentation. What I could find was plenty of conflicting information and data sheets that might as well been written in Greek.

Poor quality solder joints. All sensors came with signs of corrosion.