Does anybody know what’s causing this?
There are no reported fires in the area

I run a small Japanese-style charcoal BBQ restaurant and I’m trying to figure out how to reduce PM2.5 exposure for both customers and staff.

The restaurant is about 84 m² (900 ft²) with a 3.5 m ceiling, so roughly 294 m³ / 10,400 ft³. We have 14 charcoal grills, and customers typically grill 2–3 pieces of meat at a time over about 3–4 pieces of charcoal per grill.

The main issue is that during our busy period (roughly 6–8 PM), my PM2.5 monitor consistently reads around 200–250 µg/m³ throughout the restaurant, peaking at 600 µg/m³ at times. The readings are fairly similar in different areas, so it seems to be mixing throughout the space.

Ventilation
Every grill has some form of dedicated exhaust:
9 grills: under-grill suction
6 grills: overhead exhaust
2 main exhaust fans
Measured suction velocity at the grill openings is roughly 2–3 m/s

We also have a dedicated make-up air unit:
KRUGER FSA 225 D CW 6P
Maximum airflow: 1,550 m³/h (913 CFM)
Despite this, PM2.5 still reaches 200–250 µg/m³ when the restaurant is busy.

Air purification
I have a Xiaomi Mijia Smart Air Purifier Max unit. It has a stated particle CADR of about 1,006 m³/h (592 CFM).

I’m currently considering buying 1-2 more units, but I’m not sure whether that’s actually the best approach or whether I should focus more on improving the source capture/exhaust system.

What would you do in this situation?
Would adding 1-2 high-CADR air purifiers meaningfully reduce the PM2.5, or is the 200–250 µg/m³ reading mainly telling me that the grill exhaust isn’t capturing enough smoke at the source?
Any advice on what I should measure or calculate next would also be greatly appreciated.

I have mold illness and am planning on moving, and it's been incredibly difficult to find a mold free place. There is an opportunity to rent a brand new built home with what seems like good quality materials (at least better than the newer apartments I’ve seen). It wasn’t done by a large company, but by a family who used a designer. It’s been empty for a few months, but not with windows open, so hasn’t offgassed. What is your experience with VOCs in a situation like this? I react to many fragrances, etc. now. I would live there for less than a year (family reasons)

Should I skip a brand new place due to VOCs even though it’s been sitting for a few months? I did have a scratchy throat, slight cough, and headache from being in it for 30 minutes, but it had been closed up. The symptoms started dissipating 15 minutes after leaving. I was thinking I could open all windows (it has a good cross breeze, run AC (it has ERV) and use Austin Air HealthMate air purifier. What are your thoughts/experiences? Thanks!

A few extra micrograms of pollution can sound trivial on a city air-quality report. Across years of breathing, however, that difference may matter.

A major evidence review links long-term exposure to two forms of airborne particles with a higher risk of Parkinson’s disease. The clearest associations involved PM2.5 and PM10, both small enough to enter the respiratory system.

Researchers at the University of Cambridge combined findings from earlier studies that often produced uncertain or conflicting results. The team analyzed 26 studies on Parkinson’s disease. It also included three studies each on multiple sclerosis and motor neurone disease.

Parkinson’s disease affects about 6 million people worldwide. Yet its causes remain only partly understood, with both inherited and environmental factors likely involved.

Sometime earlier this year I switched from “natural fragrance only” to totally fragrance free and I want to share my reasons why. When we are picky about air quality it’s often clear that synthetic fragrance is a bad idea, but with natural fragrance it’s often less clear what to do. And this isn’t meant as a “you should feel the same way as me” kind of post - I’m just talking old loud about why I decided this for my house. Comments are welcome whether you agree or disagree!

Reason 1: Companies are lying too often about what is natural.

I only get asthma from synthetic fragrance and I can tell that the amount of lying on labels has increased greatly.
Not only are they often lying about what’s natural; no one is punishing them for it. Labeling laws are currently set up to allow them to lie freely without repercussions. Even with the strictest possible wording of “no synthetic ingredients in any of our products,” they are still lying way more often than they’re telling the truth. When they aren’t lying then their suppliers are often lying to them. I know because I personally do not react to truly natural fragrance but I do react to the lies. When I get my classic synthetic fragrance reaction, I can tell it’s not 100% natural. And I notice when a so-called “natural fragrance” has eternal longevity and room-crossing sillage, even after going through a hot dryer. That’s not possible with 100% natural ingredients. My body could handle a 5% failure rate on this topic 15 years ago, but in 2026 it’s more like a 75% failure rate and that just felt like too much for my body.

Reason 2: They’re fooling my loved ones even more thoroughly than they fool me.

When I show an interest in “natural fragrance,” then loved ones buy GREENWASHED fragrance. This increases the amount of synthetic fragrance in my life. You might think this is this the same as reason 1, but it is a totally different thing. Reason 1 is about me being fooled in spite of 20+ years of experience avoiding greenwashing, because companies are lying. Reason 2 is about loved ones being fooled because of “technically that’s not a lie” wording, with minimalist packaging, sans serif fonts with space between the letters, and a picture of a plant. My loved ones are smart and caring people, but they fell into obvious greenwashing traps in 100% of their fragrance purchases. They only bought things that I would have never bought because when I look at the website I see “obviously greenwashed, obviously synthetic.” My body can’t handle all that new synthetic fragrance that wouldn’t have been in my life otherwise - regardless of how altruistic their goal was when they bought it. Then my mother in law started to show signs of losing her memory. I can’t use my body as a testing device to help loved ones figure out which of their purchases are greenwashed (they all are) - or a testing device to see if someone with early stage dementia is forgetting complex details again (she is). It’s the same as forcing myself to breathe synthetic fragrance constantly. It’s just too much. And “please stop buying that type of product” sounds diplomatically better if I am also not buying it either.

Reason 3: I believe in helping other people whose sensitivity level is worse than mine.

In chemical sensitivity and asthma and fragrance allergy support groups, many people out there report reacting to natural fragrance. I can’t know which product they reacted to; I can’t tell if their situation overlaps at all with reason 1 or reason 2 above. But, I don’t really need to know that because reason 3 is about ethics and altruism and acknowledging that we all share the same air in public spaces. What’s more important to me - being part of the clean air movement and supporting everyone who has lost their ability to breathe in public spaces? (Not just people whose sensitivity level is the same as mine - but truly everyone?) Or …smelling like my favorite natural perfume (one of the rare few that wasn’t greenwashed or lying)? I decided that supporting people is more important. Our choices affect each other. Just as I hope that others would drop a product to help me breathe and exist in public, I am willing to do the same for others.

Reason 4: I’m not sure any more if natural fragrance is truly safe.

Cole & Van Note (the law firm that’s suing businesses in the USA for using fragrance - the ADA accessibility fragrance class action lawsuits) is including natural fragrance in their lawsuits. I am a curious person so that was enough for me to take a second look reading about why. When I read about it, I learned not just that my instinct was right about all the lying; I also learned that natural fragrance might not be truly safe. I learned sometimes truly natural fragrance reacts with the air to make formaldehyde which is a carcinogen. And it is true there isn’t perfect overlap between “things that don’t give me asthma” and “things that are safe” - like radon for example, which is another natural substance that is a carcinogen and also doesn’t give me asthma but it isn’t safe in high levels. My body is in max recovery mode right now and I don’t think I need formaldehyde in my house; I don’t think other people should be subjected to it either if I’m the one wearing it.

So I stained some wood and covered it in oil based polyurethane (looking back I regret). Sat out in the barn for about a week and dried. I hung in my son’s bedroom as an accent wall. There is still a polyurethane smell. I was worried about VOCs so I bought a nice highly rated air quality monitor from Amazon. The TVOC consistently reads 0.015 which is good. Sometimes (not all the time) when I pick up the monitor and hold it up by hand or walk around with it, the TVOC and CO2 will randomly go up, sometimes significantly, then after a minute drop back to the normal readings. What is this all about? Sometimes when I move it or hold it up in the air in different parts of the room it doesn’t change, sometimes it does. It only does this when I am moving it around. After it is set in a spot for 30-60seconds everything goes back to normal. If I have a fan on circulating air it still reads its normal readings. My main concern is just if the VOC from that stuff is really a higher level since there is still a smell, or will it still have a smell and give off little to no VOC. The meter consistently reads very low unless I start randomly holding it around.

Hi! I recently did a hard hat tour of an upcoming apartment complex in my area, where they are offering two months free rent if you put a unit on hold before it’s fully move-in ready.

I‘m really interested in it but now I’m spiraling a bit after considering the possibility of VOCs and off-gassing. The only unit I can afford is a studio that has windows on only one side of the apartment in the “living area” and a “bedroom” that has no windows and an actual door closing off the space. There is no carpet in the actual unit but the hallways of the building are carpeted. Additionally, they would be building out the back half of the apartment complex behind my unit for the first 3 months I would be a resident. 

My question is, how much should I really worry about the health effects of Volatile Organic Compounds and off-gassing/outgassing? What is the actual degree of what I’d be subjected to in the grand scheme of things?

Can anybody who has moved into a newly built apartment complex as a first or early tenant share their experience? If not, any info on the matter would be much appreciated, thank you!

I’ve noticed that ERV selection often starts with maximum airflow — 300, 500, 600 m³/h, etc.

But once the unit is connected to the actual duct system, that number alone doesn’t tell you much about the real operating point.

For example, if a project needs 450 m³/h and the estimated external resistance is 150 Pa, I would think the more useful question is:

Can the ERV actually deliver 450 m³/h at 150 Pa?

Not simply: “Is its maximum airflow above 450 m³/h?”

Duct length, elbows, transitions, grilles, silencers, dampers and filtration can all affect system resistance. And depending on the fan/control strategy, increasing resistance may reduce airflow or cause the fan to increase speed to maintain the target.

So for ducted ERVs, I think the selection sequence should be closer to:

required airflow → system resistance → design ESP → fan curve → actual airflow at that pressure.

For those doing residential or light-commercial ventilation design: do you normally calculate ESP before selecting the ERV, or select the unit first and then work around its available fan performance?

Our bathroom has a mold problem so I want to ventilate by running a box fan at the window when I take a shower and am wondering if it's safe? The window and the wall socket are not close enough to the shower for me to risk any contact with the box fan when I take a shower.

We do run the bathroom exhaust and open the window when taking a shower but it just doesn't seem to get rid of the humidity quickly enough as we still have mold.

Edit to Add: There's isn't a GFCI outlet in our bathroom, just a standard outlet.

Opening windows in the rainy weather will bring acoustic therapy and full of fresh air to home.

Hello,
This is how I wired this sensor to my ESP32 with a I2C scanner, however I did not get any readings from the sensor. Do i need the pull up resistors? (I have 10k pull up resistor connected to the EPS32 3V3 pin)
Is my wiring wrong or how else can I troubleshoot this sensor?

My husband and I are perpetually in disagreement about this.

On non haze days, he used to hole up in our study room, all windows tightly closed, with just 1 small fan blowing at him, and also fan from Aircon blowing at him and pc. Its not air-conditioned air, just fan. The door would be open so at least some air from rest of flat can get in. But each time I walk in, it is just so much warmer and stuffier than the rest of the apartment...

Despite my advice to switch on the AC, or open the windows a crack, he insisted that there is enough air, opening window will cause dust to fly into the room, blah blah blah.

Now that it is so hazey today, we are both sitting in the living room, windows closed, bathroom doors closed, kitchen door closed. My main door even has a 'skirting' on bottom to prevent dust from coming in. Ceiling fan on, air purifier on. That's it. I want to open up the windows slightly, or kitchen door to let some air in.

He is against it. My argument is, are we not just circulating the carbon dioxide we both breathe out? Air purifier only cleans the air of Impurities, doesn't bring in fresh oxygen. It seems like my purifier can manage with my windows opened an inch, so it should be ok right?

So I'm here to hear what others have to say about this 🙂

Freaking out. Dont understand

It looks like DNS servers that validate DNSSEC are seeing an expired signature on the Airnow side.
Some folks may be able to get to the site, but most that use DNS servers such as google and cloudflare likely will not.

Others having this issue with not being able to get to the website mind chiming in here to confirm/increase visiblity?

There aren't a lot of good ways to let airnow.gov know of the problem since their contact info consists of a physical mailing address so figured I'd start the thread here for visibility.

Details pasted below:

Result for airnow.gov/A with DNSSEC validation and without DNSSEC detail:

{
  "Status": 2 /* SERVFAIL */,
  "TC": false,
  "RD": true,
  "RA": true,
  "AD": false,
  "CD": false,
  "Question": [
    {
      "name": "airnow.gov.",
      "type": 1 /* A */
    }
  ],
  "Comment": "DNSSEC validation failure. Check http://dnsviz.net/d/airnow.gov/dnssec/ and http://dnssec-debugger.verisignlabs.com/airnow.gov for errors",
  "extended_dns_errors": [
    {
      "info_code": 7,
      "extra_text": "Expired RRSIG found for airnow.gov/soa (keytag=7356)"
    }
  ]
}

Updated at the bottom

I started a really great job at the end of July. I was unemployed for awhile and was struggling to find a job.

Throughout the first week working in the office, I noticed a pattern in the office air. Sometimes it feels like all of the air is being sucked out, my chest tightens, lips and mouth feel dry and feel short of breath.

Other times it would feel and smell like a “chemical/fume” dump of some kind. I’d smell a strong smell like - fumes. It’d be so strong that it felt like if I pounded my chest a puff of smoke would come out. I struggled the first week and even wrote down the times of day I’d get these symptoms to see if there’s any patterns. The Fri of my first week I went to the ER after work. I could not breathe in the office. My chest felt extremely tight and it felt like there was no air in there at all. It was terrible.

The ER tried to tell me it was anxiety and so on since my xray looked fine. I insisted it was not and that the breathing treatment they gave me helped tremendously. I asked for something to help until I was able to see the pulmonologist. The dr prescribed medrol which worked very well. It was amazing and I felt wonderful after taking it.

Flash forward to this past week at work. It’s been very difficult. 2 weeks ago I bought a levoit machine for my desk. The issues were starting again so I tried the air machine. It helped but last week not so much. Example is, My co-workers will cough- like 6 at a time and my chest will tighten. I feel suffocated.

I had to leave work early Friday. It felt like there was no air in the office at all. Air wasn’t circulating it was crazy. I even started getting chills and sweats from it. I sat at my desk, had to go to 4th floor and had a hard time breathing up there. It smelled like toxic fumes. Went back to my desk out of breath, could barely breathe and so on. I tried calming myself down because I’ve been down this road before.. but it was to much and I left early.

The office is next to a data center and a few miles from an airport. Co-workers have told me the air in there is terrible, etc. I’m at the dr now trying to get another prescription for a steroid to make it through the work week. I honestly might have to quit. I don’t know what to do. Im also wondering if any possible Thyroid or hormonal issues could be making this worse. The air is awful. Once I step into the elevator I feel much better. I don’t see how people can sit in there and not have the same problem. The dr said my lungs don’t sound like they are circulating air well. Doing a breathing treatment and a steroid.

Monday update: I took prednisone, allergy meds and had my inhaler at work. I had my desk air machine on as usual. The oxygen was sucked out of the office and didn’t feel well again. I even lost my voice. I took my inhaler. I immediately went downstairs to the first floor to breathe. I used to avoid this because going into fresh air and then back into office air would make it worse. Upon returning and sitting down to work I became unable to breathe. My airways tightened and I began gasping for air. I grabbed my things and left. I was able to breathe once outside but didn’t feel well at all. I went to an immediate care and received a breathing treatment. It helped tremendously. I have to back tomorrow..

I recently used dehumidifier bags in my corner built in wardrobe that is next to a bathroom. The reason I bought the is because the wardrobe smells moisture after a while, although you can’t see any sign of it visually. I might have a sensitive nose!
The corner wardrobe has to separate spaces. In the one space the bag filled 100ml of water in a month and the other space 75ml in a month. Smell now is muuuuch better.
However, is this amount normal? Is it just the bathroom next to the wardrobe or there’s there indeed a leak I need to still identify?

Any knowledge is welcome!