MQ-135 Air Quality Detector

I've thought about using these sensors, there are a series of them and each one is tuned towards specific gases.

The only problem is how do I test them without releasing the gases into the workshop?  I'd love to do an article and video about them if I could figure out a safe and practical way to demo them.

Any thoughts or suggestions as to how to do that?

Posted by: @dronebot-workshop

The only problem is how do I test them without releasing the gases into the workshop? 

Thoughts from off the top of my head.   For whatever they are worth.

Buy some plastic syringes and some plastic containers or jars with air-tight lids.

Wire the senors up with wires going through the lids and sealed with hot-glue.

Also, hot-glue a receptor for a syringe onto the lid.   Then fill the syringe with the test gas.  This can be done outside the workshop.    Then set the whole shebang up with just air and the sensor in the sealed container.   Calibrate the sensor for pure air.   Then you can slowly inject a precisely known amount of gas into the container by depressing the plunger on the syringe.    This way you can even record exactly how much of the gas had to be injected before the sensor was triggered. ? 

P.S. Don't forget to wear a white lab coat in this chemistry episode. ? 

The jar can then be taken outside, cleared of the gas.  Washed and reused for multiple tests.   You may even want to do multiple tests on each sensor to see if their performance changes once they have been previously exposed to a gas.   You could end up having enough data to write an article for a Chemistry Journal.

I'm so excited I'm sitting on the edge of my seat waiting for the video to come out! ?

More B.S,...

Since the parts should be inexpensive you could even build a dozen test enclosures to you can do a dozen tests at a time in the video.   Then air them all out and do a dozen more tests.  Am I making a lot of work for you Bill or what? ? 

The other nice feature of this method is that if the sensors have specifications for how many ppm of gas they can detect. You can then calculate exactly how much gas you should need to inject into the jar in order to reach that critical level to trigger the sensor.  You could do a FANTASTIC test where you could even check to see if they actually trigger when the correct amount of gas is injected.

Oops!  I just fell off the edge of my seat! ? 

That's how excited I am.

I can hardly wait to see Bill in his white lab coat. ? 

I used to work as a chemist at one point, so please forgive my overzealous excitement for this project.

@dronebot-workshop

I saw this one advertised for €4.29 on eBay, it claimed to detect Ammonia, Methane, Smoke, Aromatic Hydrocarbons and Benzole amongst other things, and all with one sensor. I really don't believe it!

An unserious suggestion would be to run a hosepipe from the car exhaust into the workshop and you could do the video in WW2 gas mask! But caution, I don't think that WW2 gas masks can handle Carbon Monoxide. I worked for four months in the Eurotunnel and we all carried CO rebreathers, used by miners and these only functioned for about 15 minutes, enough time to get out to a safe area! And as your videos are around thirty minutes long, your chances of survival are slim to none!

I hereby withdraw officially my request for a demo on this item, because I want to see more DroneBot Workshop videos! ? 

Posted by: @robo-pi

I can hardly wait to see Bill in his white lab coat.  

I'm on Amazon right now looking for one!

Sounds like you have this pretty well thought out! 

Posted by: @robo-pi

Calibrate the sensor for pure air.

That would have been a lot easier back when I lived in Hawaii, the air quality is excellent there. Today in Montreal we are under a smog alert (because it's 20 below zero and everyone who owns a fireplace is using it).  I do have cans of compressed air but I'm not sure how "pure" they are.

I actually LIKE this idea, the only thing I'm not sure about is the source of some of the gases.  I know you can get nearly anything at some industrial supply places, but I believe you need to buy big (and expensive) quantities?  Of course, I can get some carbon monoxide from my car exhaust and I'm sure a few of those gases can be made at home with some simple chemistry.

By the way, I found a great list of all the "MQ" gas sensors. Some of those gases (i.e butane, ammonia) would be easy to get.  I'm electrically heated so I don't have a source of natural gas, currently, I have two propane cylinders buried under a meter of snow in the backyard by the barbeque!

Posted by: @dronebot-workshop

That would have been a lot easier back when I lived in Hawaii, the air quality is excellent there. Today in Montreal we are under a smog alert (because it's 20 below zero and everyone who owns a fireplace is using it).  I do have cans of compressed air but I'm not sure how "pure" they are.

That's a good point.  When you get those sensors you might discover that your workshop is already a hazard zone! ? 

But look at the bright side.  You'll save money on hazardous gases.  Just use some workshop air to trigger the senors. ? 

Posted by: @dronebot-workshop

By the way, I found a great list of all the "MQ" gas sensors. Some of those gases (i.e butane, ammonia) would be easy to get.

Yes, get sensors that you can easily get the gasses for.

By the way, I just thought of a really COOL experiment you can add to your video to make it really awesome!

I noticed that one of the sensors on the list detects Ozone.   That could be your "bonus experiment" at the end of the video.

Put the sensor in large container with a high-voltage Tesla Jacob's Ladder .  See how long it takes to generate enough ozone to trigger the sensor.

Posted by: @dronebot-workshop

By the way, I found a great list of all the "MQ" gas sensors.

By the way, looking at that code on that page it appears that these sensors actually report ppm values.  I was originally thinking that they were just set to trigger at a certain ppm level.  I didn't realize they actually tell you the actual ppm.

This makes the syringe experiments I suggested even more exciting since you can calculate the ppm values you can expect knowing the volume of air in the jar and the volume of gas injected by the syringe.   You can actually measure the precise concentration of the gasses.

Yep, now you HAVE to to these experiments.   It's getting too good to be true!

This will be a blockbuster hit of an DBS episode. ? 

You can report on how the readings change with every cc of gas you inject into to a jar.

Posted by: @dronebot-workshop

I'd love to do an article and video about them if I could figure out a safe and practical way to demo them.

One week on baked beans, Bill !

Not to be pushy but here are some nice plastic syringes with caps at Amazon.  I think plastic aquarium tubing might also fit on the ends of these if you wanted to rig up some fancy plumbing.   I'm also not sure if 5ml of gas will be enough.  But if you are using small enough jars it should be plenty.   That can also depend on how potent the gas is that you are using.   Anyway, just ideas for whatever they're worth. ? 

Posted by: @zeferby

Posted by: @dronebot-workshop

I'd love to do an article and video about them if I could figure out a safe and practical way to demo them.

One week on baked beans, Bill !

Or one day on Sauerkraut and Buttermilk! That really flushes your system ? 

Well obviously I'll need to accept this topic, to be honest, it's one that I've wanted to do for a while.

Accepted with the caveat that I'll only demonstrate using gases that I can obtain and that are safe to use within the confines of my unventilated workshop!

?

Bill