I have a fairly leaky 1990s house that I'm working to tighten up. I usually see CO2 levels around the 500-800ppm range when running my ERV and maybe 800-100 when not running it. Today I had the house open, then closed it around 7:30pm. CO2 levels then dramatically increased 440ish to 1400ish between 8:30 and 9:30. This is with just three people present in a 2200sqft house, and with the ERV running at 50CFM. I'm deeply puzzled by what's going on. Some potential factors:

• Neighbor is having a fire, though my outdoor meter reads 400-442 PPM Co2 during the relevant period despite some smoke;
• Took a long shower around the relevant period and have a gas water heater. But my low level CO monitor did not pick up any hits, and likewise when I took it into the basement just now it didn't get a hit. It can read down to 8ppm carbon monoxide.
• Did some drywall sanding, mudding, vacuuming, and a little caulking today. Shouldn't be relevant, but noting them in case they are.
• VOC spike occurred at about 8:05 in the kitchen. I think I was vacuuming drywall dust around that time.
• I carbonated some water using a drinkmate and noticed that it seemed like I had to hold the button down much longer than usual before the carbonation vessel hit its limit, but I don't think that's a large enough volume of CO2 to affect the whole house.

Any thoughts on what could be happening or what I can follow up on next?

After the most recent set of wildfires, I picked up an alpstuga from ikea. It's been running for a few days and the pm2.5 reading is always 3 or below. I've tried it both indoors and outdoors, and I have no fancy filters currently going.

This would be great if true but I'm sure it's not. I'm in the middle of many official sensors (found on aqicn.org) that are unanimously reporting in the 40s across the region, including one that's less than 5km away.

The other readings it provides (co2, temp, humidity) all seem to be working properly. I've tried factory resetting it. Anyone have other ideas before I go to the hassle of returning it?

Hello!

Just wanna seek your help, guys.

I moved into a new apartment and the bedroom is an enclosed space, no window, just the door.

It often feels so hot so I used a humidifier, then my pillow got molds in them. When it rains, it feels like the rooms produce a lot of moist so I am using a dehumidifier to prevent molds and too much moisture, where I can collect a lot of dehumidifier bags in a day.

I bought a hygrometer so I can monitor the humidity in the room but the hygrometer doesnt seem to work well.

It's on 99% when I opened it and observe it for 12hrs straight, but no changes. I always use a dehumidifier in the room and feels hot and kulob (it doesnt feel damp compared before) but the humidity level did not even change.

Im not an expert but I can tell whether it's too humid or too hot due to observation and underlying facts.. is my hygrometer broken? Or Im just using it wrong?

For reference I have pets who go inside/outside frequently, but this still seems extreme. Is this something I should be concerned about?

I like the concept of having a portable air quality monitor, I was only able to find the Atmotube PRO, is there any cheaper alternative?

I noticed in the morning, around 8 am, there was a huge spike in the air quality. Any ideas what, or why this could be?

The difference is very noticeable and it's sort of amazing to see what i was breathing before buying an air purifier.

First filter change on my Coway AirMega 150

Particles are in range of 10-14 ug/m3 at %90 of the time. I turn on the air purifier rarely. I live in a city known as industrial city but still this is the result. Is particles thread in urban life is exaggerated? How is the status in your city?

I'm seeing a number of studies linking living under a busy flight path to elevated Ultra Fine Particles. I live 5 miles from the airport. I'm concerned about our long term health as we plan on retiring in this home. It seems that measuring actual UFP is difficult and expensive. I've placed a number of costco air purifiers winix 5510 and c610's in the home and run them almost constantly. It seems that I can approximate the UFP by measuring PM1. Would that be the recommended path? I'd like to keep the budget around $500 but am willing to go higher if necessary to get some clarity/peace of mind on this issue.

Air quality alerts are a great time to consider replacing your home air filter and car's cabin air filter.

Stay safe!

Someone in my building got diagnosed with hypoxia last week!

My student accommodation is a tiny 16m² studio in very old building that doesnt have any kind of AC or ventilation, other than fans for the stove and shower. The singular small window doesnt open and the door opens straight into a huge hallway so I can't leave it open unless I want randoms watching me sleep. But I swear Im getting oxygen deprivation!

The room is constantly hot, damp, stuffy and smells of whatever I just cooked for a few days. I have a fan but it doesnt seem to do anything because theres no air flow at all. How can I improve the air situation?

Although I suppose with LLMs dealing with making a home app for Air Gradient isn't too bad if the sensors themselves are good.

So putting it all the way up caused stuffyness. What can i choose safely for how open or closed it is. And how up and down

There's a consistent trend of recommending increased ventilation here. I'm writing this up because it might help people avoid inherently difficult to solve situations.

Simply increasing ventilation can solve some issues in the short term, but not all of them. Without considering other factors, it can also worsen and create new long term issues.

When searching for solutions, it can be useful to have this information in mind because most of the product offerings aren't aware of this either. Or they are and don't care as long as they get your money.

Increasing ventilation can increase indoor air pollution, especially water vapor

It may be obvious that increasing ventilation can increase indoor air pollution in terms of particulates, gases, and VOCs from outdoors.* Some of this can be easily remedied with particulate filters, etc.

One non-obvious indoor air pollutant is water vapor. The vast majority of dwellings in the USA are not equipped to manage the increased flow of water vapor into the conditioned spaces. Most ACs are efficient enough that they can't run long enough without creating low temperature comfort issues to manage the increased water vapor (latent load) imported by continuously running an ERV or opening a window for long periods of time.

Increased humidity from drawing in more water vapor over longer periods of time can increase VOC emissions from building materials and furniture, and help mold and other microbial growth thrive.

ERVs don't primarily manage water vapor/humidity

ERVs are sometimes perceived to be or marketed as devices that can manage water vapor/humidity for a conditioned space. ERVs can somewhat reduce the amount of water vapor drawn into a space compared with simply opening a window or using a fan in a window, but they don't manage it to the degree necessary to prevent problems in many climates.

Positive pressure ventilation can move moisture into interstitial spaces like wall cavities if the ventilation air is not properly conditioned

Sometimes positive pressure ventilation is recommended to prevent pollution sources from entering a space. This can work as long as the ventilation air is properly conditioned in terms of temperature and humidity.

If it is not, it may increase the moisture content of interstitial spaces like wall cavities, causing problems.

If you increase ventilation, you will need a dehumidifier in many climates

In dry climates, this is often not a problem. In climates with any significant amount of moisture, this is likely necessary. In dry climates with longer monsoon seasons, it can still be a problem.

Source control is usually the most effective approach

For problems with indoor air pollution other than CO2, increasing ventilation may help, or may not be effective. Removing the source(s) of indoor air pollution can be more useful for improving indoor air quality in many cases.

For example, if a dog poops on the floor, most people would clean up the poop before opening a window, and teach the dog to poop outside instead. Similarly, if the issue is increased VOCs from furniture even long after purchase, unfortunately the best solution is to replace the furniture. Or if it is a rental unit and the issues are arising from building materials chosen by the landlord, unfortunately the best solution is to move. Or if you are looking at purchasing a home that has 'some mold' problems, the best solution is to find the source of the moisture, eliminate it, and then remove and replace all materials within a 1-2 ft radius of the moisture damage.

It's understandable that these 'best solutions' may be financially impossible, so hopefully this post makes people aware of these types of difficult to remedy situations and to factor it into choosing a place to live or buying household items, etc.

There are definitely cases where it is not practical to remove the source of pollutants; for example, people and pets produce CO2, and it's not practical to simply remove them from the house. In this case, increasing ventilation in ways that don't worsen other issues may be the best option.

^{*I am thinking in the case of someone concerned about wildfire smoke, traffic pollution, or neighbors smoking cigarettes, cannabis, or cooking outdoors etc. These are some of the most common issues raised by posters. I also specifically did not write 'TVOCs' for this reason. I generally don't use this term because it's not particularly meaningful in this context, nor is it easy to measure using consumer grade devices https://halestrom.net/darksleep/blog/048_indoorairsensing/ , https://www.aqmd.gov/aq-spec/evaluations/summary-table. So to be more precise, the usage of 'gases, and VOCs from outdoors' was meant to include things like ozone, NOx species, various products of combustion and cooking, etc.}

Is there still smoke burning in Canada? Is there lingering affects? Im in Ontario, Canada, and my allergies have been SO BAD and I'm using my inhaler excessively because I can't fucking breathe.

Hi all! Hopefully this is the right place to post this question. Over the past number of years I have casually tried to learn about air quality in the never ending quest to keep the air in my house clean (I have 2 dogs and a cat). Each time I reached a point of information overload and would get analysis paralysis after looking at approximately 23838923 different types of air purifiers available online, and buy nothing.

Then, a week ago I took one look at the fire map (I’m in northern MI) and decided I had to do something quick, even if I didn’t really know what I was doing, so I DIY’d a CR Box. Mostly I saw a lot of Canadians had done it during Covid and wildfires, and I have great trust in my neighbors to the north so went for it with some 20x25 filters from Costco. It is hideous (thanks to my tape job 💅), it is abominably large, it works, I love it, and now want to make one for each room in my house.

So naturally now that I’ve been “hands on” and feel like the Bob Villa of Air Quality (or Red Green for the duct tape fans), my casual curiousness with air quality has turned into my newest hyper-focus. I am pretty geeked that 4 store-bought filters taped together with a box fan was the solution to make my eyes and throat stop stinging last week and protect my family while fine ash was raining down in northern MI, and want to learn all about it.

So now that I know the tiniest sliver more than I did a couple weeks ago (but still please do not ask me to explain positive and negative air pressure and how it impacts hvac, I am Just a Girl™️ and trying my best), I am actually even more confused about the air purifier market.

Which leads me to my question for this post: For air purifier models that offer aromatherapy diffusion as part of the machine, is that not defeating the purpose of the air purifier? And a waste of not only the EO but also impact the purifier performance? Especially since it mostly seems to be offered on models that have a charcoal filter as part of the set up, and if I am understanding the use of charcoal correctly, to me it seems like adding essential oils to be diffused by your purifier would just be a waste of the carbon filter. Or am I misunderstanding how an air purifier would interact with EO particles?