Air Quality Meters: Particulate Matter – 2 Simple Tests

Air quality meters are increasingly commonplace in modern society, and in part, this was linked to the COVID pandemic, which bought attention to air-borne particles, including contagious viruses.

In this useful article, we will be explaining what air quality meters and air quality monitors are, how they work, what they measure and will show a real demonstration (using fire and smoke) to demonstrate how effective they can be, the highlights of which are in this video:

We will discuss the air quality monitor results from this test looking at blowing out a tealight candle and striking a match in more detail later. Before that, did you know?…

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As well as being experts in leak detection, we also offer a local damage management service in York and the surrounding area, we provide this service to leading UK insurance companies who trust us to deliver a professional and reliable service to their customers. We utilise air quality meters as part of this restoration process.

What Air Quality Meters Measure

Clearly, there are a wide variety of air different quality meters, at different prices, each of which measure a range of specific things. Some air quality meters measure just one thing whereas others measure multiple things to measure air quality.

The particular air quality meter that we used in our test, measures:

1. PM2.5 Particulate Matter (particles under 2.5 microns)
2. PM10 Particulate Matter (particles under 10 microns)
3. AQI – ‘Air Quality Index’ to score air quality overall
4. HCHO – aka Formaldehyde (see GOV.UK Formaldehyde)
5. TVOC – ‘Total Volatile Organic Compounds’

These are all potentially harmful and may come from different sources (as we will see later) and have different measurement methods and safety levels. For our the air quality tester we used in this, here are the details on what they measure and various thresholds to measure potential risk:

As you can see, the levels for each potential air quality contaminant vary and are measured in different ways. For example the PM2.5 and PM10 counts the number of particles whereas, for example, TVOC is Mg/M³.

You will also notice that, looking at the amber levels, it says ‘unhealthy for sensitive groups’ which is a really important thing to understand about air quality testers and the air quality monitor ratings. They are an indicative guide. Clearly, someone who suffers from respiratory issues, is in poor health etc may be more susceptible.

It is also important to point out that, because they generally do not always (like PM2.5 and PM10) tell you what the particles are, different things have higher or lower risk and this will vary by person. For example, and we will discuss this more later, an asbestos fibre is generally far more risky to household dust. Plus, even with something like household dust (or pollen) someone with allergies may be more at risk than someone who is not.

Potential Sources of Readings on Air Quality Meters

There are a huge number of things that could be potentially measured by air quality meters and that will depend in if you are using them as indoor air quality meters or measuring outdoor air quality. Here are some of the things that could be part of that:

• Household Dust – one of the most commonly occurring things
• Pet Hairs & Dander – from cats, dogs or other pets
• Mould Spores – especially if you have damp and mould
• Smoke – either from candles, fires or smoking in the property
• Pollen – which can come from plants, trees and flowers
• Bacteria & Viruses – again, a wide variety
• Contaminants from Cooking – including cooking smoke
• Sprays & Aerosols – from cleaning products, deodorant etc
• Possibly even Asbestos – which is clearly very hazardous

As qualified local experts in asbestos testing in York, we understand where asbestos is found in homes including asbestos in artex ceilings (and other textured coatings). That final article we just linked to has a lot of useful information in it, it is well worth reading.

Later we are going to look at a guide to what sizes these could be, but first, to help understand that, we’re going to explain how small some of these particles are, especially PM 2.5 and PM 10, in comparison to a human hair.

Particle Size Analysis – PM2.5 and PM10

We mentioned earlier that both PM10 and PM2.5 were measures of particles below 10 and 2.5 microns (aka micrometres) respectably. But how big is that?

Well there are 1,000,000 or 1 million microns in a meter, therefore:

• 1cm / 1 centimetre is 10,000 microns
• 1mm / 1 millimeter is 1,000 microns
• 0.1mm is 100 microns
• The symbol for microns is µm

You can see on the scaled down diagram above that the green arrow is 100 microns and next to that, for comparison, is an average human hair at 60µm. Clearly that is very small, but you can see that PM10 is just one-sixth of that and PM2.5 is one-quarter of PM10. So PM2.5 is 24x smaller than a human hair!

You can see how sensitive professional air quality meters need to be to detect things that small, detecting things that would not be visible to the unassisted human eye. Next we will compare some sizes of items we mentioned earlier in comparison with each other.

Particle Size Comparison

Starting from the top, you can see that people refer to three categories of particle size. Firstly, ‘inhalable course particles’, then smaller than that are the ‘fine particles’ with smallest being ‘ultrafine particles’. In reference to visibility of this (and this may vary by person), generally items smaller than 5 microns is not visible to the human eye, without help – for example from a microscope or other forms of magnificiation.

Below that section, shown in purple, is how this fits in with respiratory elements. Specifically, this is whether or not they are small enough to be breathed into the lungs and how far they can go into the deeper parts of the lungs (including the alveoli) and even beyond, potentially into the organs.

Below that, in the white numbered section is the scale for particle sizes in microns. You will notice that the scale is not linear, as it helps to group ranges of sizes. It is important to remember that these numbers are just a guide and there are things that can affect these ranges. For example – it is a bit like saying how big is a stone? The answer is it depends as stones come in different sizes and classifications. Plus stones can be crushed to be smaller!

After that, the middle section shows where PM10, PM2.5 and where HEPA (High Efficiency Particulate Filters) operate. We discuss this further in our article about air scrubbers, which work to filter air, including after a fire or whilst working to remove mould from walls. Speaking of which, on to the last part of the chart.

The final section in yellow shows indicative ranges most commonly seen for various airborne contaminants, including mould spores, bacteria, viruses, dust, smoke, smog and asbestos.

Some useful external resources to read more about these groupings and sizes:

• The Wikipedia Particulates page
• A more detailed list of particle sizes on the engineering toolbox
• See also our own article about mould in houses

Now let’s look at the results from the video at the top of this page, doing our air quality meter tests.

Air Quality Testing – Results

In the video, we did a quick and simple, small scale test of how an air quality monitoring meter reacts to smoke and soot from blowing out a candle and lighting a match then blowing it out. We discuss smoke damage in our guide to electrical fire causes.

The results shown on the air quality meter are relatively self-explanatory. However, you could see that (within 30 seconds) both of the 2 tests showed greatly elevated readings of contaminants in the air for both PM10, PM2.5 and particles per litre and both reached ‘hazardous’ levels as per the scale shown earlier.

No doubt you will be familiar with the smell associated with lighting a match and blowing out a candle. Well that is your nose detecting the smoke and soot particles, including after blowing them out. The purpose of this test was to show how something so small can cause the readings to rise from the contaminants and particles in the air. As we say in the clip, imagine the amount you would get in a house or kitchen fire.

This will depend on the fire classification, scale of the fire, the length it burns and the materials that burn. Speaking of which, and on a similar subject, we have a great article explaining the fire triangle. We also discuss candles in our article about Christmas fire safety.

Air Quality Meters – Top Tip
“Although air quality meters are an invaluable piece of equipment, it is important to understand their capabilities and limitations. They can help understand air quality in a number of areas but not necessarily what the direct cause / source of that is.

Leak Detection Team

Air Quality Meters – Conclusion

As we have seen in this article, air quality meters and air quality monitors are a really useful resource in the modern world, with a number of beneficial applications. With the health risks associated with indoor air quality, getting warnings or readings can help you think about mitigation measures, such as air filtration devices or smart air purifiers.

As you can see in this article on the BBC about air quality, we spend an estimated 90% of our time inside, so indoor air quality is important. The article also discusses health risks from poor air quality and pollution.

Although we utilise a number of professional air quality meters and other measuring devices, like many things, there are cheaper alternatives available from high street and online retailers, some of them are smart air quality meters / air quality monitors. If you are concerned about air quality in your home or business, including from mould spores in the air, contact us for help.

Air Quality Meters – associated articles:

• Remote Monitoring Equipment
• How to reduce humidity
• Hazard Symbols
• Damp Meters
• How to read a water meter
• Ultrasonic Leak Detection

We hope you found our guide to air quality meters and particulates informative. Please feel free to contact us for help at any time and we can explain any of our services, such as our professional fire and flood restoration service.

At Rainbow Restoration – York & Yorkshire Coast we are experts in Fire and Flood restoration and in Flood Damage and also Water Damage Restoration, so if you need help getting your residential landlords association property back to normal after an incident, get in touch with our friendly local team who will be happy to help you with this. We are based in York and help find water leaks in York.

Air Quality Meters – Useful FAQs

Our local team are just a phone call away and will be happy to discuss your needs and how we can help you with any problems you have with your home. We have a highly experienced team who have dealt with many of these issues, including mould in houses, for many years and that is invaluable knowledge that can assist you.

We are trusted and used by several of the UK’s top insurance companies as well as a number of other local organisations such as property management companies, landlords, letting agents and other local businesses. They trust us to deliver an excellent service for their customers, and so can you.