Hey everyone, welcome back to My Weird Prompts. I am Corn, and I am joined, as always, by my brother and resident expert on just about everything technical.
Herman Poppleberry, at your service. And I have to say, Corn, today is a breath of fresh air. Quite literally.
I see what you did there. But you are right. Our housemate Daniel sent us an audio prompt today that is literally about the air we breathe. He just got a new high efficiency particulate air filter, or a hepa filter, and a sensor for the house. And it got him thinking about all those numbers you see on air quality apps.
It is funny how once you get a sensor, you start seeing the world differently. You stop thinking of air as just empty space and start realizing it is this thick soup of microscopic matter. Daniel was asking about the different classifications of particulate matter, or p m. Most people have heard of p m ten or p m two point five, but he noticed his new gadget tracks p m one and even p m zero point three.
Right, and he wants to know why we have all these different buckets. Is it just marketing, or is there a fundamental difference in how these particles behave and how they affect our health? I think this is a great topic because, especially here in Jerusalem, we get those dust storms from the desert, but we also have the usual city traffic and wood burning stoves in the winter. It is a very localized experience.
Exactly. And to really understand this, we have to start with the scale. When we talk about particulate matter, we are talking about things measured in microns. One micron is one millionth of a meter. For a bit of perspective, a single human hair is roughly fifty to seventy microns wide. So, when we talk about p m ten, we are talking about particles that are ten microns or smaller. That is about one seventh the width of a hair.
So p m ten is basically the big stuff. Dust, pollen, mold spores. Things you can sometimes see if the light hits them just right in a dusty room.
Exactly. And then you have p m two point five, which is two point five microns or smaller. This is often called fine particulate matter. These are mostly produced by combustion. Think car engines, power plants, forest fires, or even just frying up some onions in the kitchen.
Okay, so those are the standards. But Daniel’s prompt specifically mentioned p m one and p m zero point three. These are significantly smaller. Why do scientists and sensor manufacturers feel the need to break it down even further? Is a p m one particle really that different from a p m two point five particle?
It really is, Corn. And it comes down to two things: how they travel through the air and where they end up in your body. This is where the biology gets a bit intense. Your body actually has a pretty good filtration system for the big stuff. P m ten usually gets caught in your nose or your throat. You cough it out or sneeze it away. But p m two point five is small enough to travel all the way down into the deepest parts of your lungs, the alveoli, where the gas exchange happens.
I remember reading about that. But if p m two point five can get into the lungs, what does p m one do? Does it just go even deeper?
It goes beyond the lungs. That is the scary part. P m one particles are small enough that they can actually cross the blood air barrier. They can enter your bloodstream directly. Once they are in your blood, they can travel to your heart, your brain, and other organs. There is a growing body of research, including studies highlighted by the World Health Organization in their updated guidelines, linking p m one exposure to systemic inflammation, cardiovascular disease, and even neurodegenerative issues like Alzheimer’s.
That is a massive jump in terms of health implications. It is the difference between a respiratory irritant and a systemic toxin. So, when Daniel is looking at his p m one levels, he is looking at the stuff that can actually bypass his lungs' primary defenses.
Precisely. And then you have p m zero point three. Now, this one is particularly interesting because of the physics of filtration. You might think that the smaller a particle is, the easier it is for it to slip through a filter. But that is actually not true.
Wait, really? That seems counterintuitive. If I have a net, the smaller fish should get through more easily, right?
You would think so! But at the microscopic scale, particles don’t just move in straight lines. Large particles, like p m ten, have a lot of momentum. They hit a filter fiber because they can’t turn fast enough. We call that inertial impaction. Medium sized particles might just graze a fiber and get stuck. We call that interception. But the tiny, tiny particles, like those below zero point one microns, are so light that they get knocked around by individual gas molecules. They move in a chaotic zig zag pattern called Brownian motion.
Oh, right! Because they are so small, the literal air molecules are big enough to push them around.
Exactly. And because they are zig zagging so much, they are actually very likely to bump into a filter fiber and get stuck through a process called diffusion. So, very large particles are easy to catch, and very small particles are also relatively easy to catch. The hardest particles to catch are the ones right in the middle, where they are too small for impaction but too large for significant Brownian motion.
Let me guess. Zero point three microns?
You got it. That is why p m zero point three is the industry standard for testing hepa filters. It is known as the most penetrating particle size, or m p p s. If a filter can catch ninety nine point ninety seven percent of particles at zero point three microns, it is actually even better at catching particles that are smaller than that.
That is fascinating. So Daniel’s sensor tracking p m zero point three isn't just showing him extra small dust, it is showing him the exact size that his new hepa filter is working the hardest to stop.
Exactly. It is the stress test for his air purifier. If his sensor shows a spike in zero point three, and his filter is running, he can actually see how effective that specific unit is at tackling the most difficult pollutants.
I want to talk about where these different sizes come from, because I think that helps people identify what is actually happening in their homes. If I see a spike in p m ten, I assume I just need to vacuum or that there is a dust storm outside. But what causes a spike in p m one or p m zero point three?
Indoors, the biggest culprit for the ultrafine stuff is cooking. Specifically, high heat cooking. If you are searing a steak or using an older gas stove, you are releasing a massive amount of p m one and smaller. Also, candles and incense. People love the smell, but a burning candle is basically a tiny factory for ultrafine particles and volatile organic compounds.
I remember we had that discussion a few months back about the hidden air quality in kitchens. It is wild that frying an egg can sometimes create a higher concentration of p m one than standing next to a busy road.
It really can, because the volume of air in a kitchen is so much smaller than the outdoors. Outdoors, p m one is almost entirely about combustion. Diesel engines are a huge source. In fact, a lot of the older diesel trucks you see around Jerusalem are pumping out massive amounts of these sub micron particles.
So, if Daniel sees his p m one levels go up while his windows are closed, he should probably look at the stove. But if they go up when the windows are open, it is likely traffic or maybe a neighbor’s wood fireplace.
Exactly. And this brings up a really important point about the sensors themselves. Most of the consumer grade sensors, like the one Daniel bought, use a method called optical particle counting. They shine a laser through a chamber of air and measure how the light scatters when it hits a particle.
I imagine it is hard to accurately measure something as small as zero point three microns with just a cheap laser and a photodiode.
It is incredibly difficult. Most affordable sensors are actually only counting the larger particles and then using an algorithm to estimate the smaller ones based on typical distribution curves. It is a bit of a mathematical guess. Now, higher end monitors, like the ones from companies like Alphasense or some of the professional grade Plantower sensors, are much more accurate, but even then, p m zero point three is right at the edge of what low cost optical sensors can detect.
So, we should tell Daniel to take the specific number for p m zero point three with a grain of salt? It is more about the trend than the absolute precision?
That is a great way to put it. If the number goes from ten to one hundred, something definitely happened. Whether it is exactly one hundred or actually eighty five is less important than the fact that there was a ten fold increase. It tells you to turn on the fan or close the window.
You mentioned earlier that p m one can enter the bloodstream. I want to dig into the why of that a bit more. Is it just size, or is it also what these particles are made of? Because a grain of sand at zero point three microns feels different than a droplet of half burnt diesel fuel at the same size.
You are hitting on the chemical composition, which is the second order effect that often gets ignored. Larger particles like p m ten are often crustal matter. It is basically ground up rock or plant bits. It is annoying, but it is relatively inert. But the smaller you get, the more likely the particle is a complex chemical cocktail.
Because they are products of high temperature chemical reactions, right?
Exactly. You get polycyclic aromatic hydrocarbons, heavy metals, and various sulfur and nitrogen compounds. And because these particles have a very high surface area relative to their mass, they act like little sponges. They can soak up other toxic gases from the air and carry them deep into your body. So, not only is the particle itself small enough to enter your blood, but it is also carrying a payload of other nasty chemicals.
That is a grim image. It is like a Trojan horse for toxins. It makes me wonder about the regulatory side of this. If p m one is so much more dangerous than p m ten, why are most government regulations still focused on p m ten and p m two point five?
It is mostly a legacy of technology and history. We have been measuring smoke and dust for a long time. The sensors for p m two point five became reliable and affordable for governments in the nineteen nineties. P m one is just harder to measure consistently across a whole city. But that is changing. Some cities are starting to deploy ultrafine particle counters, but it is expensive.
It feels like we are in this transition period where the personal technology Daniel has is actually ahead of the official government reporting. In many cities, the official air quality index might say good because the p m ten is low, but if you are standing next to a bus idling, your personal p m one sensor might be screaming.
That is exactly why Daniel’s interest in contributing data to a project is so cool. There are these citizen science networks, like Purple Air or the Sensor Community, where people hook their sensors up to the internet and create a real time, high resolution map of air quality. It is much more useful than a single government station located on a roof five miles away.
I love that. It turns a weird prompt into a community service. But let’s talk about the Jerusalem context for a second. We live in a city that is thousands of years old, with lots of stone, but also very modern traffic. How does that play into these different p m sizes?
Jerusalem is a perfect case study. During a Khamsin, which is the desert wind from the south, our p m ten and p m two point five skyrocket because of the sand and dust. It looks orange outside. But that dust is actually relatively large. It stays in your upper respiratory tract. You feel it in your throat.
Right, you get that scratchy feeling.
But on a cold winter night in some of the older neighborhoods where everyone is burning wood for heat, the p m ten might look okay, but the p m one and p m zero point three are off the charts. That is the invisible danger. You might not see the orange haze, but you are breathing in combustion byproducts that are far more toxic than desert sand.
So the advice for Daniel, or anyone listening, is to look at the profile of the air. If the p m ten is high but the p m one is low, it is probably natural dust. If the p m one is high, you have a combustion problem nearby.
Exactly. And that should dictate your reaction. For dust, a simple mask or just closing the windows helps. For p m one, you really need that hepa filter running at full blast, because those particles are small enough to seep through the tiny gaps around doors and windows.
Let’s pivot to the indoor side for a bit more. Daniel mentioned his hepa filter is doing its thing. For people who don’t have a fancy sensor, what are the biggest things they can do to manage these niche particle sizes?
Ventilation is the double edged sword. If the air outside is clean, opening a window is the best thing you can do to clear out the ultrafine particles from cooking. But if you live next to a highway, opening the window might be making it worse. This is where the sensor is a game changer. It tells you when it is safe to ventilate.
And what about the source control side? We talked about cooking. I’ve read that even the type of oil you use can change the particulate matter output.
Oh, absolutely. Oils with low smoke points, like extra virgin olive oil, will break down and release huge amounts of ultrafine particles if you use them for high heat frying. If you are searing, you want something like avocado oil, which has a smoke point around five hundred and twenty degrees Fahrenheit, or clarified butter. It sounds like a cooking tip, but it is actually an air quality tip.
That is a great takeaway. It is not just about cleaning the air; it is about not polluting it in the first place. I also want to touch on the p m zero point three measurement again. You said it is the most penetrating size. Does that mean a standard N ninety five mask is useless against it?
No, actually! An N ninety five mask is called that because it is rated to catch ninety five percent of particles at that zero point three micron size. Just like the hepa filter, the N ninety five mask is actually better at catching things smaller than zero point three because of that Brownian motion we talked about. So it is very effective against p m one. The problem is usually the fit. If the mask isn't sealed against your face, the air—and the p m one—will just go around the edges.
Right, because p m one particles are so small, they will follow the air current wherever it goes. If there is a gap, they are in.
Exactly. It is like water flowing through a pipe. If there is a hole, the water will find it.
This is all making me think about the future of these sensors. Daniel’s sensor is a standalone box. But do you think we will see this integrated into everything? Like, will our phones eventually tell us the p m one count in the room we just walked into?
We are already seeing it in some high end smartphones in certain markets, though it is usually a dedicated sensor. The challenge is air flow. A sensor needs a fan to pull air across the laser. Shrinking a fan and a laser chamber into a phone is a massive engineering challenge. But in smart home systems? Absolutely. I think in ten years, every thermostat will have a p m two point five and p m one sensor built in.
It makes sense. We track temperature and humidity religiously, but the actual cleanliness of the air is arguably more important for our long term health.
It really is. There is this concept of the exposome, which is the measure of all the environmental exposures an individual has over their lifetime. We are finding that these tiny, sub micron particles are a huge part of that. If we can track them, we can start to correlate them with health outcomes in a way we never could before.
I imagine the data from Daniel and thousands of others will be a gold mine for epidemiologists. They can see how a specific wildfire or a change in traffic laws actually affects the air inside people’s bedrooms.
Exactly. It moves the science from the macro to the micro. And that is where the real insights are.
Okay, so let’s summarize some of the practical stuff for the listeners. If you are looking at an air quality app or your own sensor, p m ten is the big stuff. Dust, pollen. Irritating, but usually stopped by your body’s natural filters.
Right. P m two point five is the standard danger metric. It gets into your lungs. Mostly from combustion.
And p m one and below, the niche sizes Daniel asked about, are the ones that can enter your blood. These are the ones you really want to watch out for if you have heart or vascular issues.
Yes. And remember the zero point three micron paradox. It is the hardest size to catch, so if your filter or mask can handle that, it can handle almost anything else.
And finally, source control. Watch your cooking, your candles, and your ventilation. A sensor isn't just a toy; it is a tool to help you change your habits.
Well said, Corn. I think Daniel is going to have a lot of fun—and maybe a little bit of anxiety—watching those numbers move. But knowledge is power. Once you know that frying bacon sends your p m one through the roof, you start using the exhaust fan every single time.
Or you just start eating more cereal. Which is probably better for your heart anyway.
True. Although, have you seen the dust that comes out of a box of cornflakes? That is a whole different p m ten problem.
Ha! Fair point. No one is safe from particulate matter.
It is a microscopic world, and we are just living in it.
Well, this has been a really deep dive. I feel like I understand that little sensor on our shelf a lot better now. It is not just air quality, it is a window into the physics and biology of our environment.
Absolutely. And I love that Daniel is getting into the data side of it. Maybe we can convince him to set up a dashboard for the whole house.
Knowing him, he probably already has one.
You're probably right.
Well, before we wrap up, I want to say a big thank you to everyone for listening. We have been doing this for over five hundred episodes now, and it is the community and the questions like Daniel’s that keep us going.
It really is. We love diving into these technical rabbit holes with you all.
And hey, if you are enjoying My Weird Prompts, we would really appreciate it if you could leave us a review on your favorite podcast app or on Spotify. It genuinely helps other curious minds find the show.
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Thanks for joining us in the soup today, everyone.
Stay curious, and keep those filters running.
Until next time!
Goodbye.
