It is impossible to see or smell air pollution in your home. So it is useful to have an air quality sensor to test the air in various parts of your home. Also very important for everyone who has an air purifier to have a device to test air quality. Otherwise, it is possible to use an air purifier for years not realizing it is not working well, is the wrong model, is in the wrong place to be effective, etc…….. So you breathe in more pollution than you intended. This may affect your health and so it is very important to check air quality with an air quality meter.
An air quality monitor is essential to gauge the quality of air in your home. If you are using an air purifier you are very unlikely to use it optimally without an air quality monitor showing if you are effectively improving air quality. So you may save a few dollars not buying one but end up with worse health outcomes.
In medical trials when people were given air purifiers they only managed to reduce airborne particle count by 50%, nowhere near the EPA’s minimum standard of at least an 80% reduction.
Having a stand-alone air quality sensor is so useful in avoiding problems. Such as switching the purifier to a lower setting because of noise and not realizing that the air quality at the lower setting is not adequate. This is particularly an issue during sleep when you may turn the air purifier down so it is quiet. Then years later when you buy an air quality sensor you find that you have been breathing polluted air for 7-8 hours at night.
It is also useful when first installing the air purifier to see if the air is adequately purified by the purifier. Also, HEPA filters are delicate and can be damaged in transit, so it is best to check the quality of the air after changing the filter.
Having an air quality meter will also help you learn more about air quality and so change things to improve it. For instance if you take a reading in the kitchen before cooking and then cook you will see a marked increase in particle count.
Models
Bangood Air Quality Meter ($35)
AQ measurement and Particle Count no Chemical Measurement
This costs $35 and has the Plantower 5003 laser particle sensor in it using multi-angle laser scattering detection. If you cannot get hold of one with a Plantower 5003 sensor then a 7003 sensor is equivalent. There is now a Plantower 9003 sensor, but I do not have any data for that. It draws the air through the sensor by it creating thermal currents of air. So there is no need for a fan which would make the sensor more prone to mechanical failure.
This meter measures quickly in real-time. The readings change markedly from second to second, as different samples of air go through the sensor. As you watch the reading it will vary in proper time and you will need to take an average value.
The image at the top of this post shows a range of air quality meters with readings in exactly the same air. On the left is the Banggood $35, then the Temtop !000LKS $120 and Temtop M2000 $160 and lastly the Trotec PC 200 $1000. As you can see the cheaper the monitors, the lower the particle count. When I put the meters into air from the outlet of an air purifier that has no particles in it, both the cheapest and most expensive registered zero particles whereas the other 2 did not. This non-zero problem makes it difficult for you to assess the meaning of the readings as you.
Any of these particle counters would give you a ballpark idea of how effective your air purifier is. Of these personally, I find the Bangood and Trotec easier to use because at zero particles they give a zero reading.
The Plantower 5003 and 7003 sensors were used in a paper in Nature, one of the world’s leading scientific journals.
| Advantages | Disadvantages |
|---|---|
| Background scientific data | Displays in real-time so measurements vary in real-time |
| Cheap | Actual particle count too low but does vary with air pollution |
| Portable-can record in your car-plug it into the 12 volt supply with an adaptor | No battery so needs plugging in to a source of electricity |
| Measures and displays a wide range of particulate data | |
| Easy to compare readings to both readings from an EPA recording station and a high-end reference particle counter. So can use both methods to check that it is giving accurate readings. |
None of the cheaper sensors are perfect, but an air quality monitor with this Plantower 5003 sensor (SainSmart) was tested by South Coast AQMD . This is a governmental agency responsible for regulating air quality in southern California. They found the monitor to be more accurate than many air quality monitors in the $200-$1000 range.
Kaiterra Laser Egg ($149)- AQ measurement only no particle count there is a version that measures chemicals Laser Egg+ ($200)
This was Wirecutter’s 1st choice based on the particle count behaving in a way that they would expect given the particle count. The Kaiterra like many monitors measures the mass of pollution ie PM2.5 which is a standard measure of pollution. It does not measure the number of particles. This made it difficult for them to compare their very accurate particle counter (which did not give a total mass of particles) to the Kaiterra measurement of the mass of particles. So they based their view on a correlation between their particle count and the Kaiterra’s PM2.5. I am not aware of any more detailed laboratory data of the type that South Coast AQMD has published for some other sensors.
The Kaiterra also measures PM2.5 in units-you may prefer a monitor that measures in 0.1 units. There is a variant which checks for chemical pollutants in your home-the Kaiterra Laser Egg 2+ Chemical. There is extensive smart phone integration and the devices are HomeKit enabled.
Temptop M10 ($80)-AQ measurement only, no particle count, measures chemicals
This was Wirecutter’s 2nd choice again based on how the readings on the monitor varied with their particle count. There is also a lack of hard data of the type that South Coast AQMD has measured for other sensors.
This air quality monitor also measures chemicals (TVOC) in the air.
iQair AirVisual Pro ($270)- AQ measurement and PM2.5, no particle count, but the supreme air quality meter for consumers
IQ air is very well respected brand and produces air quality sensors. When tested by South Coast AQMD in their laboratory study the sensor reading correlated well with the reference machine. The IQ air sensor was the most accurate sensor being 30% more accurate than the cheapest air quality sensor.
This device measures PM2.5 to within 0.3ug/m3 and is accurate enough to stake your health on it. As you can see it measures many other features of yoru indoor air quality and can be linked to your home smart system. It integrates with IFTTT software so that it can trigger action by devices in your home it air pollution rises or could contact you to let you know. There is also a smartphone app. In additon there are optional outdoor pollution measuring stations, these are nice for the curious but not essential, you could always take the basic indoor meter outside for a few minutes if you want to know what the air quality is like outside.
Dylos ($260-$460)-Particle count only
A well-respected laser particle counter that gave readings that were as accurate as an approximately $4000 Fluke meter. It has been used in scientific studies.
Drawbacks of Inbuilt Air Purifier Sensors
They Use Inherently Less Accurate Technology
They do not use laser particle counters and which counts particles by analyzing scattering of the laser beam. Instead, they use a cheaper arrangement such as an infrared emitting diode and a phototransistor. This relies on the particles blocking the light from reaching the phototransistor-the more particles the less light reaches the phototransistor. So a crude measurement of the number of particles in the air is performed, and the result displayed as 3 or 4 grades of air purity. This technology is nothing like as accurate as analyzing the scattering of a laser beam by particles in the air.
The Location of the Sensor
As the sensor is built into the purifier it so can only measure the air quality at this point. It cannot tell you the quality of the air that you are breathing in the room somewhere else. There may be factors such as air leakage into the room that means the air pollution will be different where you are in the room. Also, it will not tell you if you have the fan speed of the purifier on high enough to purify the air in the room.
The Response of the Air Purifier to the Sensor is Sometimes Too Weak
I have seen manufacturer’s accept good air quality as up to an AQI of 100 which is equivalent to a PM2.5 of up to 35 ug/m3. However we know that health effects start with a PM2.5well under 12 ug/m3, as outlined in this article. This means that in accepting a PM2.5 of 34 ug/m3 as good air quality the air purifier will be running at its lowest air flow whereas really it should be running on a high airflow. So this is another reason that you should not use the in-built sensor.
Actions speak louder than words. Top of the range air purifiers do not have inbuilt sensors eg iQair Healthpro Plus. Also reputable companies such as Medify have removed inbuilt sensors from for instance their Medify MA-40 model.
Meter Accuracy Does not Really Increase Further Unless the Device Draws a Sample of Air in and Then Measures the Particles
Just having air flowing in a relatively uncontrolled way through the particle counter reduces its accuracy. It is only when the devices suck in a known amount of air and analyze it that accuracy improves.
The very accurate meters draw an accurate volume of air in in which to measure the particles and are invariably above $1000. You can recognize measuring devices that do this by the 2 chimney-like devices they have sticking out of the top of the meter. Do not be fooled if you see one small stick protruding from the top of the device-this is a passive sampling device like the other cheap sensors/meters.
How can I test the accuracy of my air sensor?
Sometimes you will probably feel that your monitor is not giving you an accurate reading. There are 4 ways of sorting this out-
Compare the Reading to an EPA Air Quality Monitor
Probably the best and easiest way to do this if you wish to test your sensor would be to drive to your nearest EPA air quality monitor location. Then get as close as possible to the sensor and compare the real-time reading from the EPA website at that location with your sensor reading. Obviously, there could be difficulties. You may not be able to get very close to the EPA monitor. Or there is some other local reason, for instance, cooking fumes from restaurants near where you are but not so near the EPA meter. You could then drive to the next EPA meter to see if it is possible to get nearer to the meter and have no interference from other things in the environment.
This method will only work if your meter gives a PM 2.5 measurement as you will not get a broken down particulate count from the EPA data. So this is another reason that having an air quality sensor built into your air purifier is not ideal. It is going to be very difficult to take the air purifier to the nearest EPA station to check the sensor to see if it is working!
Compare the Reading to High Quality Air Quality Monitor
The other way of testing the accuracy of your meter is by comparing it to another air quality meter. However, the meter that you are comparing it to needs to be of high quality. I would suggest using a reference meter that costs at least $1000. A problem with this method is that the high-end quality measurement units measure particles and rarely give a PM 2.5 measurement. So if your air quality sensor does not give a particle count, then this method is not open to you.
Send the AQ Monitor Back to the Manufacturer for Testing
Unless the monitor is under guarantee or very expensive, this is usually not cost effective.
Compare your AQ Monitor to Another Monitor
You could also check your monitor either by buying another type of monitor or comparing it to someone else’s.
Can I Use My Air Quality Meter to Save Money on Filter Changes?
You could use the air quality meter to measure the performance of your air purifier. Theoretically, you could then only change filters when the particle count goes up in the air coming out of the air purifier. Please see this post discussing this approach.
Almost all Air Sensors Miss More Than 95% of Particles in the Air
The laser particle counters above rely on the dispersion of a laser beam to count the particles. Tiny particles do not disperse the beam enough to register. So particles 0.5um diameter 100% of particles are counted but at 0.3um only 50% of particles are counted. Ultra-fine particles (UFP) are less than 0.1um and makeup 95% of particles in the air.
They can enter the deepest levels of the lungs and can even enter the bloodstream. The sensors listed above cannot count them. So there is the assumption that what happens at larger particle sizes also applies at smaller particle sizes.
To count ultrafine particles it needs more complicated measuring equipment, for instance, the TSI P-TRAK 8525-approximately $5000.
Most studies of air pollution and its medical effects have measured particles larger than UFP with sensors like those above. This is probably because the sensors to measure them are cheaper, can record for longer and need less maintenance.
You can find further information from the EPA here.
What Air Quality Reading Should I Aim For?
On a cheap meter I would suggest aiming for a particle count of 200 per liter or less and an AQI of 5 or less. This is a fairly stringent requirement. On a mid-range meter I would aim for a particle count of less than 400 and on an expensive meter less than 1000 per liter.
Conclusion
There is quite a range of air quality monitors at the lower end of the price scale from $35 up to $300. Overall, the best choice is the iQair AirVisual Pro, but it is $270. The Kaiterra Laser Egg is a good mid-range choices. If you want a cheap choice, then the Banggood $35 is the one to go for. This is also the one to go for if you want a particle reading and an AQ count.
Should you want a sensor that also measures chemicals in the air ie VOCs (volatile organic compounds) then you should consider the Kaiterra Laser Egg Chemical or Temptop M10.
If you have a limited budget, you may be better buying the cheapest particle counter and spending any extra money on a better air purifier.
Using an air purifier without an air quality monitor (one not built into the machine) is like flying blind. If you do you will almost certainly make mistakes with the fan speed and be breathing in more polluted air than you should-possibly for years. No one using an air purifier for a medical condition should dream of using it without a separate air quality sensor.