Sensors - CO2, radon ...

We consciously chose to live rural, with one of the benefits being better outdoor air quality than that found in the city ... but, what about indoor air quality? Up to this point, I've been guessing, and hoping fot the best.

I finally got the first of many sensors, so I can see what is happening, stop the guessing, and actually record some data. Our first sensor, a CO2 monitor/logger "IAQ Max" from co2meter.com arrived, and with minimal fiddling, we were recording data.  Outdoor CO2 is in the low 400's (a green category), and after calibration, it showed the same inside ... all is well.

Until we started doing things ... cook a meal with the propane stove ... numbers went up into the yellow cat egory. Heat a room with a propane heater ... numbers go up. This got us doing remediation, like opening doors and windows ... sure enough, numbers went down, and we were back in the green.

So, this will take some integration effort ... recording data, correlating to activities, and figuring out remediation steps throughout the year. But, it's a start ...

The next sensor we have coming is for radon ...

Both can be moved around as needed ... different rooms or spaces, other buildings, etc.

The sensor device itself, to add to arduino or raspberry pi boards, was somewhat costly, so I just bought the entire device, and saved some head-scratching ... but that alternative method is available as well.

Plenty of stuff to monitor these days, including "particulates" (wildfire smoke in our area) ... better (I think) to know vs not know.

Lots of research to do ...

I have the 'airthings corentium home' brands sensor for Radon . Works well... yikes now just like you said gotta vent.

Interesting find Jt.  Out of curiosity, did the house feel stuffy when in the yellow category?  Were there any perceptible sensations that you could identify with the elevated CO2?

Eric

Absolutely no symptoms, but I was playing with it, and was able to immediately open doors and get ventilation going. How long the level stays high after cooking might correlate to how drafty or air-tight the house is, or what other family members might be feeling.

Part of the research remaining is to determine exposure stuff ... how much, what symptoms at each level, etc. What constitutes a truly bad level, and for how long?

It's not so much short-term effects, because opening a door or window seems to bring the numbers down ... the device is sensitive. It's long-term effects ... if we never knew it was a problem, how do we correlate it to other health issues that we might be experiencing? Is it worse in winter than in other seasons, when we can't open doors/windows?

No clue to these things at the moment ...

I hope the radon sensor puts that same kind of concern to rest as well ...

I think the sensors are only good for 7 years.
So I was thinking it would be cheaper to use the arduino stuff that's available.
And just replace the sensor next time.
But it sounds like the whole device is cheaper than the sensor.

Update: our CO2 average was around 500ppm (green range) when we were able to throw open doors and let in fresh air this fall; we did a reasonably good job of that day and night, just by paying attention to natural ventilation with doors & windows. Normal propane cooking activities drove levels into yellow range all the time, but ventilation drove it back down. Need to pay attention to throwing doors and windows open ...

Our first big cold snap came through, and IAQ suffered ... ppm levels went into the yellow range and stayed there ... with some effort, it would occasionally dip into green levels. Here's the rub ... every instance of propane ventless heater kicking on drove ppm levels into the red, and as it's cold outside, we can't throw open doors and windows else it's a vicious cycle of heat/cold air. We have a "drafty" home, but that doesn't help ... air quality drops in the winter.

When we complete the kitchen rework, there will be a wood-fired kitchen cook stove in the mix, and I expect a further hit to CO2 levels from that ... I hope there are IAQ ventilation methods for such woodstoves ...

Short answer, need a better (automatic) ventilation method for winter season ... something active (powered fans venting out?).

On to radon ... Got our Airthings Corentium radon device in, and we are at the same level of radon as outside air, after a few weeks of testing. So far, so good here ... draftiness probably a good thing, in this one category of air quality.

No "particulates" monitoring happening ... no devices identified yet.

Hope this helps others ...

The first thing we did when we bought our land was dig a hole, put a radon detector in it, and then put a trash can lid over it and sealed dirt around the edges / on the lid. Came back and a week later and had steady readings around ~17. Well above the healthy limit but not as bad as numbers in the hundreds some of my east coast friends have. I was planning on having a vapor barrier anyway, but knowing that radon is a problems makes you a bit more careful when building a house to ensure that you're not basically building a large radon capture device.

To make you feel a bit better about the pollution from your gas range, here's an nytimes article about it: https://www.nytimes.com/wirecutter/blog/dont-need-ditch-your-gas-stove-yet/

Having a range hood nearly zeros out any problems from a gas range, Not sure if you have one but they're not too tricky to install (depending on your home).

Hmm ... humidity is an indoor air quality problem. Didn't pick up on that ...

Indoor Humidity: apparently, too much is not good ... 45% being a number to stay under. Luckily, the CO2 monitor also shows indoor humidity, so I can track that as well.

Outdoor humidity is watched via an AcuRite Atlas weather system (indoor display, outdoor sensor array). This helps us keep an eye on outside weather conditions, mostly lightning ... we either hear thunder somewhere, or see lightning numbers going up on the display, and outside work ceases until storms move away.

Hi Jt,
Specifically to your propane ventless heater kicking on and putting the readings into the red zone... rather than looking at an "automatic ventilation system", I think I would suggest getting rid of the ventless heater and get one of the direct vent models. I know the ventless are sold and touted to be safe... but clearly based on your readings it would be better to put that exhaust outside.

These days the CO2 monitor is useful for assessing covid risks of poor ventilation in crowded spaces. They say we should be okay re the virus when CO2 levels are less than double the background level ie 415 ppm. This is increasing every year as we know with climate change emissions

Jt Lamb wrote:We consciously chose to live rural, with one of the benefits being better outdoor air quality than that found in the city ... but, what about indoor air quality? Up to this point, I've been guessing, and hoping fot the best.

I finally got the first of many sensors, so I can see what is happening, stop the guessing, and actually record some data. Our first sensor, a CO2 monitor/logger "IAQ Max" from co2meter.com arrived, and with minimal fiddling, we were recording data.  Outdoor CO2 is in the low 400's (a green category), and after calibration, it showed the same inside ... all is well.

Until we started doing things ... cook a meal with the propane stove ... numbers went up into the yellow cat egory. Heat a room with a propane heater ... numbers go up. This got us doing remediation, like opening doors and windows ... sure enough, numbers went down, and we were back in the green.

So, this will take some integration effort ... recording data, correlating to activities, and figuring out remediation steps throughout the year. But, it's a start ...

The next sensor we have coming is for radon ...

Both can be moved around as needed ... different rooms or spaces, other buildings, etc.

I don't know why you have concern about CO2, because CO is the danger indoors. That's the gas that can kill people in their sleep and should be monitored with an alarm near open combustion heaters. (Closed systems such as high-efficiency gas furnaces and water heaters vent all gases outdoors and aren't open to indoor space.) As for CO2, it has to go very high to be dangerous; submarines allow something like 1200 ppm.

It's smart to test for radon in the soil your house is on, which can accumulate in a basement. If present, it's worth remediation. If it's not detectable, you can then forget about it.

Would the oxygen content be more pertinant than co2? I don't know what would be considered "low" but mouth to mouth resus works with the 10-12% (from memory?) you breath out so quite a margin perhaps? I didn't think a small increase in CO2 level had any bearing on humans directly at all? High CO2 levels is what triggers you to breathe in, not a low o2 content in your lungs, so if it was too low I think your body would tell you?
A direct vent from outside to provide fresh air next to an open or stove type fire is a good idea, and a specific room vent is an England legal requirement above 5KW.
Heating the air while circulating it with fresh from outside is something that needs to happen. Particularly pertinent in a camper for instance or the moisture build up will be nasty. Several entire room volume air changes per hour are, again from memory, the sort of changeover rates houses are designed for.
Our internal house humidity is usually about 60%, but the relevance of the relative humidity number changes with air temperature.

Heard this recently on the radio. I already knew I wouldn't have unvented gas or propane appliances again because of IAQ issues. For your stove you need an appropriately sized (cfm) and located kitchen vent that exhausts to the outside. Any heating appliances ought to be vented, never unvented. If for some reason you can't listen to the article they say that poor indoor air quality of this sort is much harder on children and can contribute to asthma.
https://www.npr.org/2021/10/07/1015460605/gas-stove-emissions-climate-change-health-effects

All good questions and concerns ... thanks for all such comments, as it helps us figure out all aspects of both our choices and manufacturers' equipment. Our ventless heater brand, Mr Heater 30k btu blue flame models work great ... we've used them for years; safe, O2 sensor and cutoff, thermostat, etc. Vented models have a number of features that didn't work for us, such as complexity of installation, visible flame, and so on ...

But then I decided to monitor IAQ, with an eye to seeing if there were any undiscovered air quality problems from *any* sources ... if I found any, then I would address them in some form or fashion. Monitoring came first; this works, because I'm now seeing the results of our choices in other areas, and can now apply short- and long-term fixes.

Short-term fixes include just getting more air exchanges, by manually opening doors/windows ... the outside air is better (wrt CO2), and monitoring shows that it works. Problem solved, air quality rapidly improves. If you aren't monitoring (and who is?), and don't have automatic air exchanges by some other system (hvac of some kind), then just do the same opening/closing of doors & windows.

Other short-term fixes would be something that addresses the kinds of heating/cooking devices we have (ventless heaters, wood stoves, cooking appliances) ... now that I know there's a problem, based on our choice of these devices, we'll implement the fixes, as we find them. We *do* have a vent hood over the propane range, but we don't use it all the time ... we'll now test that, and hopefully solve the cooking issue of IAQ, w/o giving up cooking on gas,, which we love and would never give up. Thanks for that reminder!

Long-term, an automatic air exchange system of some kind seems the best way of ensuring we get air changes without lots of effort, and would also solve the winter problem ... just now looking into this, given that monitoring reveals problems.

Curiously, first monitoring, and then *research* into the results, reveals that CO2 *is* an IAQ problem, with health effects. I don't believe we can trust the old "1200ppm, 2000ppm, or higher levels" in homes, businesses, and subs are still "good enough per EPA and others"; I'm not sure I can trust a government or other agency that values business more than people. If outside air is 400ppm, then that is *my* target. We have CO alarms, but no direct monitoring yet of CO values ... good news is that our generator isn't in the house with us!

BTW, don't monitor, if you aren't ready to tackle what such monitoring might show ... that was our first mistake : )

CO2 makes plants grow better, and they release  oxygen into the air.  As David mentioned, I wouldn't be worried about CO2 at all, but if I were, I would just grow some houseplants.  

In Central Wisconsin, we do not have the luxury of opening doors and windows all the time in the winter, and unless WE go out, we are pretty much tied to forced air heating, and yes, it is a concern for me.
My hubby [a former heating and plumbing installer] says there is nothing to be worried about, just open the windows.
He also refuses to have the vents cleaned up, [never been done here] saying that the particulates in the vent improve the tightness of the system and make our heating more efficient.
But he also says that "nowadays, houses are made too airtight".
I have no clue. I insisted we check on radon in the basement, which we didn't have so that's good.

Jt Lamb wrote:All good questions and concerns ... thanks for all such comments, as it helps us figure out all aspects of both our choices and manufacturers' equipment. Our ventless heater brand, Mr Heater 30k btu blue flame models work great ... we've used them for years; safe, O2 sensor and cutoff, thermostat, etc. Vented models have a number of features that didn't work for us, such as complexity of installation, visible flame, and so on ...

Short-term fixes include just getting more air exchanges, by manually opening doors/windows ... the outside air is better (wrt CO2), and monitoring shows that it works. Problem solved, air quality rapidly improves. If you aren't monitoring (and who is?), and don't have automatic air exchanges by some other system (hvac of some kind), then just do the same opening/closing of doors & windows.

Other short-term fixes would be something that addresses the kinds of heating/cooking devices we have (ventless heaters, wood stoves, cooking appliances) ... now that I know there's a problem, based on our choice of these devices, we'll implement the fixes, as we find them. We *do* have a vent hood over the propane range, but we don't use it all the time ... we'll now test that, and hopefully solve the cooking issue of IAQ, w/o giving up cooking on gas,, which we love and would never give up. Thanks for that reminder!

Long-term, an automatic air exchange system of some kind seems the best way of ensuring we get air changes without lots of effort, and would also solve the winter problem ... just now looking into this, given that monitoring reveals problems.

Curiously, first monitoring, and then *research* into the results, reveals that CO2 *is* an IAQ problem, with health effects. I don't believe we can trust the old "1200ppm, 2000ppm, or higher levels" in homes, businesses, and subs are still "good enough per EPA and others"; I'm not sure I can trust a government or other agency that values business more than people. If outside air is 400ppm, then that is *my* target. We have CO alarms, but no direct monitoring yet of CO values ... good news is that our generator isn't in the house with us!

BTW, don't monitor, if you aren't ready to tackle what such monitoring might show ... that was our first mistake : )

Again, CO is the danger indoors, not CO2. As the Mr Heater description I found at https://www.homehardware.ca/en/search?query=mr%20heater&categoryId=7424&gclsrc=aw.ds&gclid=CjwKCAjwh5qLBhALEiwAioods4FQXApVV-ZJOW_GF2j0uBgWlrlmWR2LJ-b7rEwr7uPL4uMHymKJfBoC-f8QAvD_BwE says "Great for industrial and commercial use" and garage heating.  Count yourself lucky if you've been using it in your home.

I know government information isn't always reliable, but safe CO2 levels have been determined scientifically. You may be confused by climate alarm material, irrelevant to IAQ (although alarmists may insist otherwise). But always use your range hood when cooking.

The only vents our house has in the UK that are always open are at the top and part of the windows, called trickle vents. You can open or close them but you can never fully close them, they still vent a bit when shut.
So since this was architect designed within the last decade I assume it must meet the number of airchanges required without any active means of it happening like an extractor fan for instance.
Do you have trickle vents?
We also have switched extractor fans in both bathrooms, and the chimney is always venting wether the fire is lit or not.
Triple glazing with loads of insulation. Sealed but vented :)

You should probably just cook outside ;)

jason holdstock wrote:
Do you have trickle vents?

As Cecile noted, those of us who live where winters are cold can't afford to leave windows open in winter. Apart from wasting heat, the resulting low humidity would contribute to nosebleeds and dry, cracked skin (especially for us old-timers).

A tight house with source and volume/rate controlled ventilation is in my opinion much better than old style where the air making the way into the house through all the cracks brings in construction dust and fiberglass.  A super tight house with no ventilation is a recipe for moisture  and other air quality problems.  I think the best we can do is all natural building built air tight but vapor open, like plastered strawbale, with source controlled passive ventilation. Heat recovery ventilation (HRV) systems for cold climates and energy recovery ventilation (ERV) systems for warm climates are a good modern high tech way to achieve fresh air in the house  while losing less energy to heating or cooling that air.
I put vents in the walls of my house for 12 v bilge blowers to be installed in the basement as extractor fans, and one vent that is impossible to close to let make up air in.  I plan to arrange it as a 'poor man's HRV' by running the exhaust air out through a 25' long plenum with the pipe for makeup air inside the plenum, so there will be some heat exchange between the outgoing air and incoming air without any mixing of them, and the materials for this are cheap- basically a pipe in a long box made of plywood scraps and air sealed with sheetrock mud.  

I bought a little camp oven to use along with a co detector.  There was never a reading above 0 on the co detector while cooking until once when the propane canister was running low and the flame had a lot more orange in it.  The reading went up to as high as 39 ppm until I opened the windows, and it quickly went back to 0, but then back up to 35 after I closed the window again, even with the flame off, so I opened all the windows for a while. The moral of that story for me was to get my extractor fans hooked up asap and always use them while cooking!   I also bought a radon test kit, which is on the way.  I have plastic on the basement floor, but its not sealed at this point.   Would it be better to put the charcoal radon collector under the plastic, or just in the air in the basement?    

(Unintentional duplicate I can't delete)

Are we comparing apples to apples?

 [ Mr Heater description I found at ... says "Great for industrial and commercial use" and garage heating.  Count yourself lucky if you've been using it in your home. ]

These heaters linked in the above post seem to be portable (camping) and commercial (garage, shop, construction site) heaters, not our 30k BTU (residential) models, which have many more safety features and are dedicated as indoor wall- or floor-mounted heaters. Even with these indoor units, the advice is "crack a window", which we've always done. If I could get or figure out "trickle vents", I would ... that sounds much better than "cracking a window". More research ...

Our propane heaters are also not setting off our current CO *alarms* (sort of like car idiot guages, as in "hey, idiot ... if you aren't dead yet, I sense a build-up of CO in this area!"), which is better than nothing ... I'll know more when we do figure out dedicated CO monitoring devices. So many devices to figure out, and perhaps *one Raspberry Pi and specialized monitoring sensors wired in* is the ultimate answer.

We are also in a cold climate, which is why, when weather precludes opening doors/windows, we'll have alternative air exchange methods (vent fans, etc.) Some great suggestions above ... thanks!

I think air exchange, however it is done, is the moral of this story ...

Along with active and dedicated monitoring devices ...

Corey Schmidt wrote: I also bought a radon test kit, which is on the way.  I have plastic on the basement floor, but its not sealed at this point.   Would it be better to put the charcoal radon collector under the plastic, or just in the air in the basement?    

The danger with radon gas is inhaling it over a considerable period of time, so testing your basement air is the way to go.

Jt Lamb wrote:...our current CO *alarms* (sort of like car idiot gauges, as in "hey, idiot ... if you aren't dead yet, I sense a build-up of CO in this area!")...

LOL! The CO alarms are intended to sound before a dangerous level is reached -- not really like car warning lights (except for the nebulous "check engine" light).

The trickle vents in previous houses in the UK I've lived in have often been a bit too drafty. A neighbour with those in quite a windy and exposed location has rain coming in them when closed. As I said, even shut they still provide some throughput. They are just plastic covers over a slot cut through the frame.
The ones in our house, not built by me, are in windows built in Sweden so can I assume if it works there the principle could work anywhere cold? No obvious external hole or vent in these ones.
I didn't realise opening the window anywhere would result in a lowering of internal humidity and that could cause health issues! I've been in hot desert with low teens humidity which was fine, I have zero experience of cold and that dry though.

We moved to a rural area last year and thought our indoor air would be better than in the city. I have been monitoring our air for the last 3 year with an AirIQ, and we noticed the CO2 was good, but the PM 2.5 was through the roof in our new (to us) home. I am guessing our dirt driveway/road to our home contributes to the high PM. We rigged up a Corsi cube, and that helped but the house is leaky and we currently do not have a range hood that vents outside, so all cooking particulate can’t be exhausted. Personally, I think you should consider monitoring your PM because those particulate get in you lungs. We plan to remodel next year and hoping to add some whole house filtration along with an ERV. So happy you posted this - I am a bit of an IAQ geek and love to see what others are doing.

David Wieland wrote:

Jt Lamb wrote:...our current CO *alarms* (sort of like car idiot gauges, as in "hey, idiot ... if you aren't dead yet, I sense a build-up of CO in this area!")...

LOL! The CO alarms are intended to sound before a dangerous level is reached -- not really like car warning lights (except for the nebulous "check engine" light).

In 2018 I was using a gas stove-oven that kept setting off the CO alarm whenever I baked for more than an hour, so I read up on it a lot (and replaced the stove with a better one).

1) Yes, CO alarms get set off BEFORE the dangerous level, because CO poisoning is really very very dangerous, both immediately, and/or in the long term.

2) CO at slightly elevated levels for a few hours is also very dangerous, and liable to go unnoticed by the occupants, which is why the alarm will be triggered after 40 ppm for a few hours.

3) In my region, installed heating systems are rare, and most people install a wood stove in the autumn and remove it every spring. People staying in a temporary living situation often use unvented gas heaters (LPG: I don't know if that's propane or what). I know a few different people who have been badly poisoned by CO at night, although the heaters supposedly have an automatic cutoff if low oxygen is detected.

4) The creepy thing about CO poisoning is that CO bonds to your hemoglobin where oxygen is supposed to ride, and the CO stays bonded much longer than O2 would. So once a significant portion of your hemoglobin is carrying CO, it can take hours to clear your blood, despite going into clear air. That's part of why a sustained slight level of CO can be as deadly as a shorter high level.

Bummer ... our range hood vents right back into the kitchen ... don't believe the filter is anything fancy, so research is needed into venting back into the attic or outside, or finding an excellent filter system? Any cooking we do is part of the problem ...

We've managed to "manage" CO2 levels with exhaust fans and door or window opening ... at least everyone is more aware now.

Radon is being measured, and while it started low, it is currently creeping on up there ... our original mitigation, when house was built, is probably not up to par. More long-term effort needed here ...

Ready to tackle particulates, so investigating the (wide-range) of portable monitors ... this looks to be another $100 monitor ...

Always vent your range hood to the outside. If you vent into your attic, it’s like you are still venting inside. Think of your home as a fish bowl, and the air in it is like water. Air gets all mixed up (imperceptibly) when you have changes in internal/external pressure, and if you vent into your attic all the humidity and particulate recirculates back into your living space. Also, if you vent to your attic, you are likely to end up with a mold problem up there because there is a lot of moisture released from cooking.  Also no venting through a soffit, this will also set you up for a mold problem. See Home Performance channel on You Tube, lots of great info on ventilation, and understanding home chemistry.

There is no mention of VOC's or PM here, which would be the first indoor air quality metrics I'd think of.