High CO2 Indoors, what's next?
July 24, 2014 4:14 PM   Subscribe

I got a new withing's scale, after the old one died when our dear deceased kitty peed on it as a final goodbye. The new one has a an air quality detector built in that reads carbon dioxide. I often suspected there was excess CO2 in the house, because I have aquariums and the ph is depressed when the house is closed up for long. But the new scale confirmed it by showing a surprisingly high reading. What do I do next?

To start out, I don't know how accurate the scales co2 reading is, but I tested it in a variety of circumstances, including outdoors, and windows open vs the house closed up. The very highest was just shy of 2000ppm, with the house being closed up for about a week and ac running. When we took it outside and when we had the windows open and fan running, it's hovering around 450ppm.

I'm not sure what to make of those readings because the outside numbers are higher than what is considered "normal" for outside, and we're in the burbs without a lot of co2 sources. Houses and cars, but I can't imagine they're emitting that much. But an acquaintance of mine who uses co2 in his lab said the 2000 ppm is really bad. The internet is all over the place on whether or not this level is bad, some sources saying anything over 1000 is bad, some saying it can be much higher without being a problem. This thread discusses the topic of what is safe.

More to the point, if the issue is high co2 when the house is closed up, we're airing the house out at least every few days in the summer when it's cool at night. I suspect it gets much higher in the winter when the house is closed up for months on end.

High co2 in the house kind of makes a lot of sense, in that I've been dealing with issues of fatigue and headaches, and other bleh feelings. In fact, I was diagnosed with Chronic Fatigue Syndrome a few years back, but mid spring, I felt better for a bit (windows were open, mild weather) and then crappy again (windows closed, AC on). My husbands been feeling kind of crappy too lately, attributing his lethargy to being bummed about losing his job. But he's also been having a lot of headaches in the past couple years, also pointing to the possibility of an issue with excessive co2

So I'm really not sure what to do next. The same acquaintance suggested if co2 is high, carbon monoxide could also be building up. I have a co alarm, but this thread suggested that they aren't always as good as they should be.

This winter was horrible for me, and while I can't believe it could be entirely due to co2, I could see how it could be playing a big factor. This past winter was especially bad, it started early, remained really cold, and ended late, meaning the house was really closed up over a long period of time.

With this in mind, the first step seems to be "figure out if the readings are accurate." I'm not sure how to do that. I do see co2 meters on Amazon. Should I be buying one of those? Or should I be hiring someone to come out and take readings? If so, what is the type of person to do this? And who/how do we chase down detecting CO if that is part of the problem?

Next is where the heck is it coming from? Our house isn't particularly air tight, if anything it's drafty (which is especially noticeable in the winter). I had a few guesses:

1) there are just that many bodies in the house. It's just my husband and me, but we have 2 dogs, 3 cats, a bird, a tortoise, and fish tanks (the algae may respire co2 at night...).

2) Hot water heater or furnace. The furnace is off this time of year, but the hot water heater is still used. The hot water heater was installed about 5-6 years ago. It's a tankless heater, replacing one with a tank and they had to put a new exhaust in. The furnace is about 4 years old, and they had to put a new exhaust in that as well. The caveat to this is that I have struggled to maintain a high ph in the aquariums for as long as I can recall, and that's a classic sign of high co2 levels in a home.

3) The fish tanks. This was my husbands suggestion. Though I think they're affected by it, not causing it. I ran an experiment and closed off the fish room while the rest of the house was opened up, and there was no significance in reading between it and the rest of the house.

4) Seepage from underground. The interwebs says this can happen. Our house is a bilevel, with the downstairs being half underground.

5) Negative pressure inside the house drawing exhaust from the water heater (or/and furnace in the winter).

I'm not even sure how to approach this issue. One confounding factor is that we're broke, and while I suspect this is a serious issue (thought I'm not ACTUALLY sure), every penny has to count. And then the question is, what can I do about it. Even if we forgo a/c all summer (uncomfortable but I'm sure we'd survive). In the winter that isn't much of an option. Or would a cracked window help the issue without making the heating and cooling bills go crazy?

I could really use suggestions on the best way to approach this issue, because I don't have an inkling of where to start.
posted by [insert clever name here] to Home & Garden (14 answers total) 1 user marked this as a favorite
Do you have a carbon monoxide detector? CO causes a heck of a lot more problems than CO2. You should have a CO detector anyways, and they are cheap. I would start there.
posted by rockindata at 4:18 PM on July 24, 2014

What about houseplants? I'm not sure how many it would take it generally lower CO2 in a house, but it couldn't hurt. This seems to be a list of the best for this sort of air scrubbing.
posted by supercres at 4:20 PM on July 24, 2014

Response by poster: I do have a Carbon Monoxide detector. But one of the linked threads had a few people suggest that residential CO detectors aren't as good as they're supposed to be. I'm not sure if that means buying a second one, or getting a professional out to test after the house has been closed up a few days.
posted by [insert clever name here] at 4:23 PM on July 24, 2014

IF those CO2 readings are accurate, then ventilation is what you need. Look into an air-to-air heat exchange ventilator for the winter. Don't worry so much about CO. High CO2 is caused by different things than high CO. In your case, well yes, you do have a lot of bodies in the house. That's probably your whole problem.

BUT: it's a scale, designed to measure your weight. I would take the rest of its measurement capabilities with a grain of salt. Dedicated CO2 monitors go for $100 and up. I would trust one of those before I trusted my bathroom scale to tell me my house's CO2 level.
posted by beagle at 5:55 PM on July 24, 2014 [2 favorites]

Response by poster: (not to thread sit but . . .)
I would normally agree with you about the reliability of a scale, but I have a few observations that had made me wonder about it in the past; the fatigue and headaches, the low ph in saltwater aquariums, and most recently, I saw a talk on using co2 to supplement algae (phytoplankton) growth, and the results that I have are similar to those where co2 was intentionally added to the cultures for improved growth. All just anecdotes, but they add up to being pretty likely the case.

The house is 2000 sq/ft if you include the finished basement. Which is why I doubted, or at least wondered, if me, the hubby and the animals could possibly be hitting that threshold. If the house were airtight, maybe. But its quite drafty.

(looking at the ventilator now)
posted by [insert clever name here] at 6:19 PM on July 24, 2014

I'm not familiar with this scale, is there a manual that says how CO2 is measured and what the best placement is to get an accurate reading?

The reason I ask is that CO2 is heavier than N2 and O2, which make up about 99% of the atmosphere, so it will sink to the lowest level, which just happens to be where the scale is taking its measurements. Can you take a reading while the scale is first on the floor and then on a chair or table? Or, if you have a ceiling fan in a room that can be closed off (you could probably use a tilted box fan if you don't have a ceiling fan), take one or more measurements in the closed room with the fan off. Turn the fan on, leave the room for a few minutes and take another reading. Leave and come back a couple more times. These tests won't won't solve any problems but they will give you a better idea of what the scale is measuring and how well mixed the CO2 is in your house.
posted by plastic_animals at 6:40 PM on July 24, 2014

I wonder if your local Fire Department could be of any help in confirming the carbon dioxide and/or monoxide levels? Couldn't hurt to give them a call or stop by the station to find out if they have more accurate testing equipment, or advice about how to make sure your water heater & furnace are properly ventilated.
posted by oh yeah! at 7:47 PM on July 24, 2014 [4 favorites]

Air is something like 0.5% CO2, so 2000-4000 ppm seems kinda low?
posted by wrok at 11:02 PM on July 24, 2014

Air is something like 0.5% CO2, so 2000-4000 ppm seems kinda low?

No, it's not. Air is around 0.04% CO2 by volume, and ambient outdoor CO2 levels should be around 350-400 ppm (and climbing...).

NIOSH (OSHA's research arm, I believe) guidelines note that indoor CO2 concentrations that exceed 1000 ppm indicate inadequate ventilation, and there is some research (though I'm not vouching for its quality) indicating that high indoor CO2 concentrations can have some insidious effects on people, so you're right to be concerned if 2000 ppm is an accurate reading reflecting the average air quality of your living space.

However, I think plastic_animals has a great point that you have to be careful about where your sensor is located. I don't have special insight into CO2 settling, but I wouldn't measure any atmospheric variable right at floor level without a compelling reason - the air is poorly mixed down there. Try placing the scale on a shelf at eye-level and see if the readings are any different.

I would also be a bit suspicious about the accuracy of the sensor they used in the scale; CO2 monitors tend to be expensive and I wonder if they used a lower-quality sensor (which would make sense since its primary use is as a scale). Just a bare sensor for use in hobbyist electronics (like this DIY CO2 sensor Arduino project) starts at $85, although your sensor may have a narrower measurement range or lower accuracy/precision.

Finally, I'm not sure if it's normal or common for aquariums to change pH when the CO2 concentration changes, but if these fluctuations are harmful to the organisms you keep in the aquariums, there might be a calcium carbonate-based buffer solution you could add that would keep the pH more constant even if you can't solve the CO2 issue. I don't keep aquariums so I don't have any practical advice, but this water chemistry primer for aquariums seems like a good place to start looking into buffering (especially if you have soft water, which has less buffering potential).

Best of luck improving your air quality! If all else fails, just try getting a whole bunch of houseplants.
posted by dialetheia at 8:38 AM on July 25, 2014

Best of luck improving your air quality! If all else fails, just try getting a whole bunch of houseplants.

Houseplants don't do much. The original nasa study was for blowing benzene-laden air past the roots of a plant. Which worked ok, and is worth considering if you live on a space station. This has been generalized in the popular consciousness to "Dudez, a spider plant will turn my apartment into the Amazon rain forest!"
posted by sebastienbailard at 10:34 AM on July 25, 2014

You need someone with a better meter to come out and confirm that you have C02 levels that you are measuring - and to help track down the source. If it is your water heater, that should be fairly easy to determine (though it sounds like you have direct vent gas appliances, so this shouldn't be an issue). If it is the basement, it should also be easy enough to figure out. Solutions for the gas appliances should be relatively easy. Solutions for the basement will be more difficult.

If no source can be found, then you will need to increase ventilation. A heat recovery ventilator (HRV) would be a good choice to maintain high air quality without wasting a lot of heating or cooling energy. It may be worthwhile to get a blower door test (generally offered by people who do energy assessments) to see how leaky your house is and if ventilation is adequate.

My first step would be to call the gas company. In my area, they would come out and have an accurate CO meter (and I'd assume C02 as well). If the gas company can't help, then someone who services gas appliances may be helpful.
posted by ssg at 10:39 AM on July 25, 2014

Houseplants don't do much.

They might not fix the entire problem, and it's absolutely true that the potential for houseplants to remove pollutants like benzene from the air has been wildly overstated.

But growing plants absolutely do take up CO2 and emit O2 - that's just photosynthesis. The faster the plant is growing, the more CO2 it's taking out of the air. Just make sure you put the plants in the highest light conditions possible and keep them growing.

Bonus: many plants display improved water use efficiency when exposed to elevated CO2 levels!
posted by dialetheia at 12:35 PM on July 25, 2014

Searching google scholar for "houseplant indoor co2" found:
Critical Review: How Well Do House Plants Perform as Indoor Air

Proceedings of Healthy Buildings 2009
Paper 667
Critical Review: How Well Do House Plants Perform as Indoor Air
John Girman1,*, Tom Phillips2 and Hal Levin3
Independent Researcher
California Air Resources Board
Building Ecology Research Group
Corresponding email: [Manually Redacted]
In the late 1980’s, research indicated that plants had the capability to remove volatile organic
compounds (VOC) from indoor air. The findings were based upon chamber studies involving
injection of a pollutant into a small, sealed chamber and following the pollutant decay, with
and without plants present. The results were striking with removal rates up to 90% in 24 hr.
Other studies examining this effect followed. Today, even a casual search of the internet will
find many articles extolling the benefits of using plants as indoor air cleaners. However, there
has been little critical analysis of the application of plants to actual indoor environments and
only a few field studies have been conducted. A critical review of results of both laboratory
chamber studies and field studies leads to the conclusion that indoor plants have little, if any,
benefit for removing indoor air of VOC in residential and commercial buildings. Finally,
recommendations for improving future studies are presented.

... So the science has been done, and people advocating houseplants for VOCs are simply wrong. (Note the review did not address CO2.)

I'd suggest an air-to-air heat exchange ventilator for the winter and the summer as well.

I've not read up more than casually on the houseplant CO2/VOC stuff, but I'd guess you'd probably want 500+ W of light driving the plants to make a meaningful difference in indoor oxygen. And that a houseplant is likely to cause indoor mold spores.
posted by sebastienbailard at 3:45 PM on July 25, 2014

CO2 is not a VOC. Plants use water and CO2 as part of photosynthesis. It is a fact that plants will consume CO2 and in the process release O2 (a very important fact for all of us). So in a closed environment plants will certainly help.

Plants do not typically use VOCs. There is not an apriori reason to assume that plants will consume VOCs - so while interesting, the study above says nothing about how plants will impact CO2 levels.

Intense light levels (i.e. 500+ W) is not a critical factor here, since it's the total light absorbed by the plant which drives the rate of photosynthesis. This does depend on the intensity of light, but depends even more strongly on the actual surface area of the plant (i.e. number of leaves). This just indicates that to have a measurable impact with typical indoor light levels you might need multiple plants.
posted by NoDef at 11:47 AM on July 26, 2014 [2 favorites]

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