Measuring household air quality

You’ve read about air quality in the media, you understand the language and the scale of the problem. But what comes next?

Finding out about the air that we breathe, where we live, is a good way of putting our knowledge into context and there are lots of things to do:

1. Start following your council’s air quality pages.
2. Sign up for text alerts about London’s air via airText.
3. Find a local air quality sensor to follow on the Breathe London network.
4. Compare your local air quality to a global view at IQAir.

These city, borough and neighbourhood sites can give information about the levels of the gaseous and particulate pollutants in the air and will often give you a more general air quality index number that you can compare to other parts of the city, country or world.

 The above are all looking at what is happening outside, in your neighbourhood and city, but what is happening indoors? The only practicable way of finding out is to use a home or personal air quality monitor.

There are lots of options for home and personal air quality monitors and they may be less expensive than you think, or even free.

1. Some councils, like Camden, offer a free air quality monitor loan scheme.
2. Your local Library of Things may have them as a loan item.
3. If you do want to buy one, there are reasonably priced ones on the market. Look at all the features, read the reviews and decide on the one that best suits your household needs. Some are small enough to be clipped to your bag or belt and go everywhere with you. Some have helpful apps for tracking and storing the data.

There is a massive difference between the types of air quality monitors used by local and central government, and any monitor that is affordable, or practical, for home use.  Even if you track a full year of data on your own monitor this won’t be comparable to the UK Air Quality Standards and WHO Guidelines, but they are a great tool for understanding what is happening in your environment.

You can expect your monitor to measure carbon dioxide (CO₂) and particulate matter (PM2.5 and PM10). Many will also measure carbon monoxide (CO), nitrogen oxides (NOx) and volatile organic compounds (VOCs).

Now that you have your monitor it’s time to experiment.

If your monitor measures VOCs then the bathroom can be a great place to start. Set your monitor up in the bathroom, or just outside the door if it needs to be plugged in and see what happens to the VOC readings when you are getting ready for the day. Comparing the difference in air quality between aerosol products and a cream or liquid can be quite a surprise, especially how long the measured VOC levels take to drop back down. The same is true for bathroom cleaning, some products have a lot of VOCs and they can be detectable by the monitor long after the smell has stopped.

You probably already have a carbon monoxide alarm in your home, and you certainly don’t want to cause the release of carbon monoxide indoors, so we will leave that one well alone.

Particulate matter (PM), especially small particles (PM2.5), is one of the most harmful types of air pollution and has been linked to several serious diseases including heart and circulatory disease, stroke, asthma, lung cancer, diabetes, and dementia. There will always be particulates in the air, both indoor and outdoor, as some is from natural sources such as pollen and sea spray, but many sources are not natural, and can be reduced.

There are countless of ways of experimenting with the PM2.5 measurements of your monitor in and around your home including:

• Cooking – try holding the monitor close to where you stand while cooking and test several types of cooking methods including frying, steaming, and grilling. What happens if the pan is on the front of the cooker versus the rear? What happens to your measurements if you use an extractor hood, and when you have the windows wide open? If you have an airfryer, how does this compare to an oven?
• Vacuuming and dusting – see what happens to the PM2.5 levels before and after dusting and vacuuming. Try a longer experiment by seeing what happens to the PM2.5 levels if you vacuum every day.
• Candles – try burning candles in a room with the windows and doors closed for a little while and see how the PM2.5 readings change. Then try the same experiment with the windows and doors open. Measure the before and after readings in the next room/hallway before and after too.
• Windows – see what happens in a room if you keep the windows closed all day, and then test leaving the windows wide open all day. This is one is much more pleasant to test in warmer weather.
• Fires – If you have an open for or wood burning stove see what happens to your indoor air quality when you light the fire, when you refuel, and during the time that it is burning. Then have a look at the outdoor readings. How close to the chimney pot can you safely get a reading? Can you take readings in your garden on a still day, a windy day, from your nearby neighbours’ gardens or any rooms downwind of your chimney? If you don’t use an open fire or wood burning stove, you can perform the outdoor test when someone else in your neighbourhood has their fire going. Test up and downwind of a bonfire, fire pit, or barbecue.
• Transport – if you have a small personal monitor, you can take it with you while walking, cycling, driving, or catching public transport. If you have a regular commute to work or education, see if there are different routes or transport modes that you can test out.
• Gardening – if you have a garden take the monitor outside when you are working in the garden. What happens when you are digging on a dry day, a still day, or when it is windy? If you don’t have your own garden a friend’s garden or a local park are good alternatives.
• DIY – see what happens to the readings if you are working in your garage or shed, if you are cutting wood, painting, or sanding.
• Neighbourhood – if your monitor is portable, you can see how localised, and variable, the measurements can be in even quite a small area. By taking measurements in different locations, or the same locations over different days you may see a wide variation in PM2.5.

If your monitor stores data you can build up a picture of air quality in your home environment, but a notebook or spreadsheet can work just as well. When you feel that you have enough data, you can reflect on the results and see where there are possibilities for improving air quality for your home, and maybe your neighbourhood. There are a large number of sources of air pollution, and a significant number of actions that we can take to improve air quality.

Please remember to take the results in context when you are looking at changes. Some activities like frying give off a lot of particulates but you may only spend a few minutes each week frying and opening the window may be enough to help offset this type of cooking. There are other activities like dusting and vacuuming that may make a small increase in particulates while you are doing it but improve the air quality in your home for the rest of the day. Outdoor measurements are variable based on weather conditions, and pollution sources, such as traffic, industry, farming or wood burning.

If you burn solid fuels for heating, consider the indoor and outdoor particulate pollution. Depending on your stove, fuel, maintenance plan and fuelling technique there may be a large, small, or unnoticeable increase in indoor particulates when in use, but your fire or stove will still emit significant quantities of particulates into the neighbourhood, often for several hours a day and some of that will be coming back into your house as ‘fresh’ air. Depending on the wind direction your ventilation may be bringing in your own particulates, that of your neighbours, or even that from homes further afield.

Affordable personal or portable air quality monitors don’t have the accuracy or features of professional monitoring equipment, but they are a great place to start, and can be an important part of improving air quality in your home and neighbourhood.