Gas sensor(s) recommendations

Could you please recommend some good (and not very expensive) gas sensor(s) for detecting (measuring level) various harmful gases for home air monitoring. Preferably, separate measurement for different gases, few sensors for different gases is also good.

Which gases do you want to detect?

hammy:
Which gases do you want to detect?

I do not know yet :-), what are my options?
CO, ozone, kitchen gas (propane, butane?), smoke, methane, hydrogen (not sure it is possible to have).

I’d suggest you decide on the gases , why you might want to measure them , why they might be present, in what concentrations, then look for suitable sensors .
This is a bit like buying a bike, aeroplane and a boat then deciding where you wanted to go .

hammy:
I’d suggest you decide on the gases , why you might want to measure them , why they might be present, in what concentrations, then look for suitable sensors .
This is a bit like buying a bike, aeroplane and a boat then deciding where you wanted to go .

Hmm, surprise for me, I always buy a car and later decide where I will go to :slight_smile:

OK, what are sensors(s) recommendations for harmful gases may be typically found in regular home (in big city)? I would like to hear people who really had a deal with sensors they would recommend...

Very cheap gas sensors are not so good and good gas sensors are very expensive. There was nothing in between, until recently sensors on a chip came available.

These are very cheap: MQ 2 MQ 3 MQ 4 MQ 5 MQ 6 MQ 7 MQ 8 MQ 9 MQ 135 Detection Smoke methane liquefied Gas Sensor Module for Arduino Starter DIY Kit|sensor module|gas sensor modulegas sensor - AliExpress.
They get hot and require some current. Because they need some current, about one or two can be used when the Arduino board is powered via a USB cable.
They can not measure a certain gas, they are sensitive for many gasses. You will never now which gas was detected. They have a certain resistance that changes with a range of gasses. It is possible to calibrate them to know the ppm, but that is not accurate.
Being very cheap, they are very sensitive. It is fun to buy one or two just to see how sensitive they are.

An example of a very expensive gas sensor is for example this: Calibrated Carbon Monoxide (CO) gas sensor - Shop.

There are versions of the very cheap sensors that require less current and don't get hot. With those you can combine a few sensors.
There are other promising sensors (I have not tried these type of sensors):

Koepel:
These are very cheap: MQ 2 MQ 3 MQ 4 MQ 5 MQ 6 MQ 7 MQ 8 MQ 9 MQ 135 Detection Smoke methane liquefied Gas Sensor Module for Arduino Starter DIY Kit|sensor module|gas sensor modulegas sensor - AliExpress.
They get hot and require some current. Because they need some current, about one or two can be used when the Arduino board is powered via a USB cable.
They can not measure a certain gas, they are sensitive for many gasses. You will never now which gas was detected. They have a certain resistance that changes with a range of gasses. It is possible to calibrate them to know the ppm, but that is not accurate.
Being very cheap, they are very sensitive. It is fun to buy one or two just to see how sensitive they are.

Thank you, very helpful brief market review.
What is the difference between all of them on that link?

OK, what are sensors(s) recommendations for harmful gases may be typically found in regular home (in big city)?

Until you specify gas type and concentration and how much you are willing to spend, no recommendation is meaningful.

The cheap ones are not selective and almost impossible to calibrate. They tell you only that something has changed, but not what has changed, and are not reliable for even that task.

SergeS:
Hmm, surprise for me, I always buy a car and later decide where I will go to :slight_smile:

OK, what are sensors(s) recommendations for harmful gases may be typically found in regular home (in big city)? I would like to hear people who really had a deal with sensors they would recommend...

EVERY gas is or can be harmful if concentrated enough. Oxygen is poison when concentrated. Too much water vapor can fill your lungs with -water-. Too much nitrogen is fatal. Too much carbon dioxide is fatal.

Better definition of what you want to measure and the concentration you are interested is what will point you to sensors.

Paul

Paul_KD7HB:
EVERY gas is or can be harmful if concentrated enough. Oxygen is poison when concentrated. Too much water vapor can fill your lungs with -water-. Too much nitrogen is fatal. Too much carbon dioxide is fatal.

Better definition of what you want to measure and the concentration you are interested is what will point you to sensors.

Lets do not bring it to absurd, will quote myself...

what are sensors(s) recommendations for harmful gases may be typically found in regular home (in big city)?

See reply #7.

Alright, have it your way.

Carbon monoxide detector is required in Oregon for ALL rental properties with any form of wood heat.

The Feds require a propane detector in ALL RVs with propane appliances. I would want one in our home if we had propane appliances.

If we had natural gas appliances, I would require a methane detector or other detector that would detect a natural gas leak.

Other than those gasses, I don't know of any that are dangerous in a home.

Paul

Paul_KD7HB:
Alright, have it your way.

Carbon monoxide detector is required in Oregon for ALL rental properties with any form of wood heat.

The Feds require a propane detector in ALL RVs with propane appliances. I would want one in our home if we had propane appliances.

If we had natural gas appliances, I would require a methane detector or other detector that would detect a natural gas leak.

Other than those gasses, I don't know of any that are dangerous in a home.

Ok, you have convinced me :-), what are recommendations for arduino-compatible sensors for carbon monoxide, propane and methane? I would also add smoke, too. Yes, I know, it is not a gas, but anyway :slight_smile:

SergeS:
Ok, you have convinced me :-), what are recommendations for arduino-compatible sensors for carbon monoxide, propane and methane? I would also add smoke, too. Yes, I know, it is not a gas, but anyway :slight_smile:

I have only purchased CO2 and propane detectors approved by the state fire marshal. No clue about Arduino and those sensor types.

The CO2 must be mounted on a wall 3-4 feet above the floor. The propane sensor must be mounted to a wall very close to the floor in the lowest part of the house, as propane is heavier than air and will sink to the lowest place.

Paul

The MQ series of gas sensors come to mind for detecting a broad range of gases, many of which are harmful in one way or another - but whether they’re suitable for your purpose depends not only on the gas you want to measure, but also:

  • will there be other gases of interest present? (they’re not very selective) If so, which?
  • what is the required sensitivity and accuracy? Do you need actual ppm/ppb values or just be alerted of the presence of a gas?
  • what is the purpose of your measurements? Entertainment or as legal requirement makes a big difference.

The vast majority of sensors can be read by an Arduino.

The problem you have is that none of these gases - CO, methane, etc should be present in your home - so your Arduino will sit there day after day detecting nothing .Doesn’t make for an exciting project , how do you even know it’s working ?

You should only use approved , tested alarms for safety monitoring.