From pea-soupers to precision sensors 

From Stoke-on-Trent's smoking bottle kilns to London's infamous pea-soupers, we have a colourful history of filthy air. But have we really cleaned up our act or have we simply made pollution harder to spot? 

Ah, the good old days. When you could see what you were breathing.

There was a time when air pollution didn't need sophisticated monitoring equipment. You could see it, smell it and, on a particularly bad day, practically chew it. The skies above our industrial towns were rarely blue, the chimneys never seemed to rest, and wearing a white shirt was an act of unrivalled optimism. But that was progress. Smoke meant industry, industry meant jobs, jobs meant prosperity and if the occasional lungful of soot was the price of economic success, well, pass the cough sweets.

Today things look rather different. Our skies are clearer, our buildings are cleaner. We've come a long way from the days when breathing in our industrial heartlands was something of an extreme sport.

Stoke-on-Trent: where the sky came in fifty shades of grey

Let's begin in Stoke-on-Trent, affectionally known as the Potteries and a stone’s thrown away from Synetica HQ, a place famous for many things. Fine china, proper oatcakes, famous footballers, even more famous pop stars and a friendly ‘ay up, duck’. And, once upon a time, an extraordinary number of enormous, coal-fired bottle kilns, relentlessly belching  out thick black smoke.

At their peak, around 2,000 bottle ovens and kilns dominated the Potteries skyline. These distinctive brick structures were essential to the ceramics industry, but they weren't exactly doing wonders for the local air quality. The air was so smoky that the sun could be obscured, and the industrial landscape acquired a permanent atmospheric filter. Long before Instagram, Stoke had perfected the art of making everything look slightly sepia.

And yet, these smoking giants were symbols of industrial pride. The irony is that today we rightly celebrate the surviving bottle ovens as an important part of our heritage. You can admire the architecture without wanting the original atmosphere thrown in.

Fortunately, cleaner firing technologies, changing industrial practices and clean air legislation helped bring the era of coal-fired bottle ovens to an end. The last traditional firing took place in 1978, preserving the skills for posterity and the air pollution to history.

London: would sir like a little sulphur with his soup?

Of course, Stoke wasn't alone in its enthusiasm for atmospheric experimentation. London took air pollution to an entirely different level. For generations, the capital was famous for its 'pea-soupers', dense, yellowish smogs caused by a particularly unpleasant combination of fog and smoke from coal fires. The nickname sounds almost charming. A pea-souper. Something wholesome and warming, except this particular soup contained soot, sulphur compounds and other pollutants. Not quite the recipe Mrs Beeton had in mind.

Then came December 1952, when the Great Smog enveloped London for five days. A combination of coal smoke, cold weather and a temperature inversion trapped pollution close to the ground. Visibility collapsed, transport ground to a halt, smoke seeped into buildings and people struggled to breathe. Around 4,000 deaths were initially attributed to the disaster, with later estimates putting the total toll at approximately 12,000. The Great Smog helped bring about the Clean Air Act of 1956, a landmark moment in our relationship with pollution.

The great British disappearing act

Fast-forward to the present day. The bottle ovens have largely disappeared, London's legendary pea-soupers are history, and coal smoke no longer routinely blankets our cities. We have cleaner fuels, better technology, stricter environmental legislation and decades of scientific progress to thank for that. And it's worth celebrating.

But somewhere along the way, we've developed a curious new assumption. If the air looks clean, it must be clean. The trouble is modern air pollution is often much less theatrical than its Victorian predecessor. It doesn't always announce itself with an enormous black cloud, it doesn't necessarily smell, and it certainly doesn't have the decency to turn the sky an alarming shade of mustard.

Fine particulate matter, nitrogen dioxide and other airborne pollutants can be present without providing any obvious visual warning. Some of the particles we're concerned about are extraordinarily small. PM2.5, for example, refers to fine particulate matter with a diameter of 2.5 micrometres or less, around thirty times smaller than the width of an average human hair. In other words, we've moved from pollution that was impossible to ignore to pollution that's remarkably easy to overlook. And that creates a rather different challenge.

You can’t manage air quality by looking at the sky

Think about the things we measure every day. We check the temperature before leaving the house, monitor our electricity consumption, count our steps, track our sleep, check our heart rates and obsess over whether we've achieved enough 'deep sleep' to justify feeling tired. Some of us even have watches that remind us to breathe, which is useful, presumably, for anyone who had forgotten. Yet when it comes to the actual quality of the air we're breathing, we're sometimes surprisingly relaxed. 'Looks fine.' A wonderfully off-hand approach to environmental science.

But air quality isn't something we can reliably assess with a quick glance out of the window. Pollution levels can change throughout the day, depending on traffic, weather conditions, industrial activity, local emissions and other factors. Two locations just a short distance apart can experience very different conditions. A busy roadside, a school playground, an industrial site and a quiet residential street may all tell different stories. Without measuring what's happening, how do we know which story is true?

From pea-soupers to precision sensors

Fortunately, air quality monitoring has come a very long way since the days when the principal measurement technique was seeing whether you could make out the building opposite. Modern monitoring technology can help us understand the pollutants present in our environment, how concentrations change and where action may be needed. Instead of waiting for the air to become visibly unpleasant, we can gather data. Instead of assuming a location is clean, we can investigate. And instead of making decisions based on what we think is happening, we can use evidence of what actually is happening.

Modern air quality monitoring solutions  help organisations make the invisible measurable. Whether the concern is traffic-related pollution, local environmental conditions or the impact of industrial activity, reliable monitoring provides information that appearances alone cannot. And importantly, measurement isn't just about identifying problems. It's also about understanding improvements. If you've introduced measures to reduce emissions, changed traffic arrangements or invested in cleaner processes, wouldn't it be useful to know whether they're making a difference?

So, how much further do we need to go?

We've gone from towns where smoke was a permanent feature of the skyline to a world where sophisticated technology can detect pollutants we couldn't possibly see. We've learnt that blackened buildings and choking smogs aren't inevitable consequences of progress, passed legislation, developed cleaner technologies and transformed our industrial landscape.

But perhaps the biggest change still required is in the way we think. For generations before us, air pollution was often impossible to miss. For us, it can be impossible to notice. And that's precisely why measuring it matters.

The next chapter in the clean air story isn't necessarily about eliminating another spectacular pea-souper. It's about understanding the pollution that doesn't make a spectacle of itself. It's about recognising that clean-looking air and clean air are not always the same thing, and that the absence of visible smoke isn't proof of the absence of harmful pollutants.

We've come a long way since the days when you could practically chew the atmosphere. Now we need to make sure that what we can't see isn't being ignored. And if we can achieve that without bringing back London's sulphur-flavoured soup, so much the better. After all, there are some things from the good old days that are probably best left there.