Public Lab Research note

The gas leak from an old apartment.

by bha | September 12, 2011 03:26 12 Sep 03:26 | #464 | #464

About a month ago, I moved into an apartment, where was built around 90 years ago.

The kitchen was renovated, so I can manage to cook and bake dishes.

The problem was bad smells from the dishwasher.

I and my wife was thinking that the smells came from new kitchen furniture and appliances.

Day by day, the smells was getting stronger. So we didn't ignore the smells any more.

I decided to make a simple sensor for gas leak.


Preheating for two hours. It was not enough, but I could get a little bit stablized output, the number is from 320 to 220.

The LED is for checking the power.

1. The bed room


At first, I checked the air in the bedroom.



The Sensor indicated about 320. I also couldn't recognize any kind of gas smells.

2. The living room

The living room is the important space where my kid usually plays.

Fortuntately, the number was not changing significantly.

3. The Kitchen

In this area, I could percieve some gas smells, sometimes, I got headaches.

Especially, I could smell a lot of gases from this gap.

Oh, my God! The numbers dramatically went up. And then, we asked the apartment manager to check the gas leak.

When specialists for gas leak came here, there were no smells any more. :(

However, I showed the sensor, and explained the situation. They changed old pipes into new ones.

Now there're no gas leaks and headaches.

Thanks, MQ-135.

P.S. I took take a test by using two MQ-135. But the same sensors generated different numbers. The gap between two sensors is about 100.

So I decided to use only one sensor in order to get more reliable results.


Awesome that you had the information to back it up! I have a gas sensor I took from a defunct CO/Gas sensor unit . Might give it a shot . :)

But next time this happens do not wait to call the gas company/landlord and pitch a fit. The odorant that is used in the gas tends to get in your nose and use get use to the smell. The headaches you experienced was probably a good indication that the level was high enough to cause issues with the oxygen in your home. Scary!!

I am glad you and your family is safe and keep up the great blog.


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Great work, the samples from different areas, and so nice that the results contributed to getting the pipes fixed.

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"The problem was bad smells from the dishwasher"

Dishwaher smells are common in my place. Think I need to build a device to detect the bad smell levels so I know when to start the cycle!!

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Thank you for your opinion. But if your thought was true, I think that I should still smell gases after changing the gas pipes.

Also the dishwasher was a new one. It has just some smells as other new products.

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Thank you for your comment, Kevin.

Now, my family lives in an apartment, which has an electric oven. :)

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can i see the circuit image?

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hi can i get to see the arduino code for this ? can you explain please ? can u attach the code here or give use the link ?

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Dear @bha, thank you for showing us how practical this MQ-135 sensor is.

Alas, none of the images on this research note are showing up today.

As a quick work around, could you edit the "" at the beginning of every image link, and change it so they start with ""? That tweak seems to make the images show up better today. (Is there a better long-term solution?)

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