As individuals, we can’t do much about the outside air. We can try to spend more time in green spaces* and away from traffic, and we can wear face-masks—as was popular in Tokyo and other such large cities long before the pandemic struck.

*The well-known mental health benefits aside (and contrary to British politician Amber Rudd’s famous assertion in a televised political debate that “clean air doesn’t grow on trees”), clean air comes mostly from trees—their natural process of respiration scrubs not only carbon dioxide, but also pollutants, from the air before releasing oxygen without the pollutants. Neat!

See also this study: Site new care homes near trees and away from busy roads to protect residents’ lungs

We are fortunate to be living in a world where most of us in industrialized countries can exercise a great degree of control over our home’s climate. But, what to do with all that power?

Temperature

Let’s start with the basics. Outside temperature may vary, but you probably have heating and air conditioning. There’s a simple answer here; the optimal temperature for human comfort and wellbeing is 20℃ / 68℉:

Scientists Identify a Universal Optimal Temperature For Life on Earth

Note: this does not mean that that is the ideal global average temperature, because that would mean the polar caps are completely gone, the methane stored there released, many large cities underwater, currently hot places will be too hot for human life (e.g. outside temperatures above human body temperature), there will be mass extinctions of many kinds of animals and plants, including those we humans require for survival, and a great proliferation of many bugs that will kill us. Basically we need diversity for the planet to survive, arctic through to tropical and yes, even deserts (deserts are important carbon sinks!). The ideal global average temperature is about 14℃ (we currently have about 15℃ and rising).

But, for setting the thermostat in your home, 20℃ / 68℉ is perfect for most people, though down as far as 17℃ / 61℉ is fine too, provided other things such as humidity are in order. In fact, for sleeping, 18℃ / 62℉ is ideal. This is because the cooler temperature is one of the several things that tell our brain it is nighttime now, and thus trigger secretion of melatonin.

If you’re wondering about temperatures and respiratory viruses, by the way, check out:

The Cold Truth About Respiratory Infections: The Pathogens That Came In From The Cold

Humidity

Most people pay more attention to the temperature in their home than the humidity, and the latter is just as important:

❝Conditions that fall outside of the optimal range of 40–60% can have significant impacts on health, including facilitating infectious transmission and exacerbating respiratory diseases.

When humidity is too low, it can cause dryness and irritation of the respiratory tract and skin, making individuals more susceptible to infections.

When humidity is too high, it can create a damp environment that encourages the growth of harmful microorganisms like mould, bacteria, and viruses.❞

~ Dr. Gabriella Guarnieri et al.

So, if your average indoor humidity falls outside of that range, consider getting a humidifier or dehumidifier, to correct it. Example items on Amazon, for your convenience:

Humidity monitor | Humidifier | Dehumidifier

See also, about a seriously underestimated killer:

Pneumonia: Prevention Is Better Than Cure

Now, one last component to deal with, for perfect indoor air:

Pollution

We tend to think of pollution as an outdoors thing, and indeed, the pollution in your home will (hopefully!) be lower than that of a busy traffic intersection. However…

• The air you have inside comes from outside, and that matters if you’re in an urban area
• Even in suburban and rural areas, general atmospheric pollutants will reach you, and if you’ve ever been subject to wildfire smoke, you’ll know that’s no fun either.
• Gas appliances in the home cause indoor pollution, even when carbon monoxide is within levels considered acceptable. This polluting effect is much stronger for open gas flames (such as on gas cookers/stoves, or gas fires), than for closed gas heating systems (such as a gas-powered boiler for central heating).
• Wood stoves/fireplaces are not an improvement, in fact they are worse, and don’t get us started on coal. You should not be breathing these things, and definitely should not be burning them in an enclosed space.
• That air conditioning, humidifier, dehumidifier? They may be great for temperature and humidity, but please clean/change the filter more often than you think is necessary, or things will grow there and then your device will be adding pathogens to the air as it goes.
• Plug-in air-freshening devices? They may smell clean, but they are effectively spraying cleaning fluids into your lungs. So please don’t.

So, what of air purifiers? They can definitely be of benefit. for example:

Air Purifiers & Sleep

But watch out! Because if you don’t clean/change the filter regularly, guess what happens! That’s right, it’ll be colonized with bacteria/fungus and then be blowing those at you.

And no, not all of them will be visible to the naked eye:

Is Unnoticed Environmental Mold Harming Your Health?

Taking a holistic approach

The air is a very important factor for the health of your lungs (and thus, for the health of everything that’s fed oxygen by your lungs), but there are more things we can do as well:

Seven Things To Do For Good Lung Health!

Take care!