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Co2 Effects On Thinking


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#1 DamonHD

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Posted 14 April 2016 - 10:03 AM

Ran across this while I should be doing other things... Thought I'd chuck it in the ring for debate...

https://www.entrepre.../article/272519

The higher the concentration of CO2, the lower the test scores. Even allowing for uncontrolled factors such as diet, previous night sleep quality and mood, employees’ overall sharpness fell by an average of 15 percent when CO2 levels reached “moderate” levels of about 945 parts per million (ppm). In modern office buildings, designed to maximize energy efficiency by letting in as little outside air as possible, CO2 levels around 1,000 ppm are common.

However, mainly because until recently carbon dioxide was thought to be harmless, the buildup of CO2 is often even higher. That’s not good. At 1,400 ppm, for instance, the test subjects’ performance dropped by 50 percent on average, and in some cases by much more. When they were breathing well-ventilated air, with roughly the same low CO2 content as in a “green” building, the employees were 172 percent better at applying knowledge to a problem, and 97 percent more effective at responding to a crisis.

Curious about the air where you work? Allen notes that there are lots of consumer-friendly carbon dioxide detectors on the market, adding that the research found that people performed best at CO2 levels of 500 to 600 ppm.

#2 Crofter

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Posted 14 April 2016 - 10:28 AM

Interesting find.
Approximately what concentration of CO2 would you expect to find in a building served by a MVHR system?

#3 joe90

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Posted 14 April 2016 - 10:43 AM

I know that in our current temporary house with no trickle vents we find it difficult to sleep without the windows open. Also my wife is finding her memory not good ( may be down to work stress) but we cannot wait to live in the country with fresh air and MVHR.

#4 ferdinand

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Posted 14 April 2016 - 10:56 AM

Arthuir C Clarke's "A Fall of Moondust" is about this, iirc.

#5 notnickclegg

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Posted 14 April 2016 - 11:15 AM

Wow, I read that 30 years ago!

Jack

#6 tonyshouse

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Posted 14 April 2016 - 11:38 AM

There are only microscopic quantities of CO2 in the air we breathe and the gas is pretty inert, I can't see the problem, more one of perception.

#7 DamonHD

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Posted 14 April 2016 - 12:04 PM

Tony, a large body of science (not even AGW science) says you are wrong, and this is a widely understood phenomenon: all we are arguing about is the numbers.

CO2 is clearly toxic to us (indeed fatal) at high enough levels, eg:

http://www.ivhhn.org...w=article&id=84

So what happens below those air levels that may impede our bodies keeping blood levels low enough (or indeed high enough)?

Damon

#8 SteamyTea

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Posted 14 April 2016 - 12:06 PM

"Wow, I read that 30 years ago!"
Longer ago for me.

I would like to see a proper report on this, their website don't actually say a lot.
What exactly is 'Crisis Response Score'? Are there absolute values for it? How does the score vary between professions and education? Can you double blind it? Why make 24 participants change building when you can just pump in CO2 to the normal workplace? Can you exclude 'other factors' i.e. better light, heating, noise levels?

#9 jsharris

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Posted 14 April 2016 - 01:00 PM

View Posttonyshouse, on 14 April 2016 - 11:38 AM, said:

There are only microscopic quantities of CO2 in the air we breathe and the gas is pretty inert, I can't see the problem, more one of perception.

Pretty inaccurate, I'm afraid.

I've posted evidence here before (measured by my own kit) that shows that houses rarely have air with the same CO2 concentration as the open air outside. Outside air is around 400 ppm CO2 (0.04%) and I found that our old house rarely gets to less than about 500 ppm, and our bedroom (with a permanently open window) was getting to to 1600 ppm (0.16%) or higher in the middle of the night.

CO2 is the primary cause of death by suffocation in enclosed spaces, not hypoxia. Even a modest decrease in blood pH (acidosis caused by reduced CO2 exhalation, due to the increase in the partial pressure of CO2 in the air in the enclosed space) will induce a range of physical effects, from hyperventilation initially (as the body tries to exhale more CO2 by increasing respiratory rate) through to unconsciousness and then death.

#10 Paul10000

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Posted 15 April 2016 - 09:39 AM

Jeremy, how did you measure the CO2? I can see some MG811 type sensors for around £25- easy enough to connect to an Arduino I suppose.

Paul

#11 SteamyTea

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Posted 15 April 2016 - 09:52 AM

I thought raising CO2 levels reduced hyperventilation, why people that have panic attacks breath in from a paper bag.
http://www.healthlin...yperventilation
There was a bit in my comic a while back about using CO2 for medical purposes, can't remember what now though.

#12 jsharris

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Posted 15 April 2016 - 10:02 AM

View PostPaul10000, on 15 April 2016 - 09:39 AM, said:

Jeremy, how did you measure the CO2? I can see some MG811 type sensors for around £25- easy enough to connect to an Arduino I suppose.

Paul

I used a Non-Dispersive Infra Red sensor, that is self-calibrating. The MG811 (I have one here on my desk) is hopeless, it needs a great deal of power, significant signal processing to get a usable signal, is non-linear and needs calibration, which puts it outside the realms of being DIY usable.

I managed to buy a job lot of surplus GE NDIR sensors that had been destined for use in a commercial product, and they were easy to use as they output serial data on command, already translated to ppm. Because they self-calibrate, they also tend to be more accurate than other types of sensor.

If you do a web search for NDIR CO2 sensors you will find a few around as modules. They tend to be expensive, though. The surplus ones I purchased were around £20 each including postage from the US.

#13 jsharris

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Posted 15 April 2016 - 10:22 AM

View PostSteamyTea, on 15 April 2016 - 09:52 AM, said:

I thought raising CO2 levels reduced hyperventilation, why people that have panic attacks breath in from a paper bag.
http://www.healthlin...yperventilation
There was a bit in my comic a while back about using CO2 for medical purposes, can't remember what now though.

I'm only going on the aeromedical training I received, which tended to concentrate on things like hypoxia, hypothermia, survival etc. I remember the doc telling us clearly that CO2 build up was initially compensated for by the body increasing the depth of breathing, in an attempt to drive the CO2 out, and then increasing the frequency if that didn't work. I also remember being told that people in enclosed spaces died from the CO2 build up, not oxygen depletion, as the rate of oxygen depletion was a lot lower than the rate of CO2 build up.

The effect is dependent on changes in partial pressure. If you halve the pressure of air, then you also halve the partial pressure of the oxygen and CO2 in it. The same applies if you change the relative concentration but keep the pressure the same. If you half the percentage of oxygen in air then you half the partial pressure, or if you double the concentration of CO2 in air you double the partial pressure. The exchange process between haemoglobin and air relies on the difference in partial pressures, with the partial pressures of CO2 and oxygen in haemoglobin being fixed largely by chemistry and our blood pressure.

So, at sea level and a normal atmospheric mix of gases our gas exchange system works normally. CO2 can transfer from our blood to our exhaled air, as the concentration of CO2 in air is normally lower. Similarly, the higher partial pressure of oxygen in air drives it into our blood, where the partial pressure is lower.

If you increase the partial pressure of CO2 in the air we breathe, even keeping the total air pressure the same, then you will decrease the rate at which we can exhale CO2. The effect doesn't need a massive change, going from the normal 400ppm to 800ppm halves our ability to get rid of CO2, but luckily we have plenty of reserve capacity to deal with a change like this. Increase the partial pressure of CO2 to a higher level and you start to reach a point where the body cannot adjust for it anymore just by changing the depth and frequency of our breathing. It's at that point where we start to suffer from the effects of CO2 poisoning.

One reason that breathing an increased partial pressure of CO2 can control some breathing disorders is because there is a very close control loop between depth and frequency of breath and blood pH. You can increase blood pH by breathing into a paper bag, because the CO2 concentration will increase, reducing the partial pressure and reducing the bodies ability to exhale CO2. The initial compensation system the body uses is to breathe more deeply, increasing the effective surface area of our lungs, so increasing the area for gas exchange. Often this first stage of deep breathing will slow down the breathing rate for a short time, long enough to "reset" whatever mechanism had caused hyperventilation. Exactly the same principle applies to using this technique to get rid of hiccups, although in that case the deep breaths and slowed respiration allow peristalsis and respiration to get back in sync.

Edited by jsharris, 15 April 2016 - 10:23 AM.


#14 DamonHD

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Posted 15 April 2016 - 10:23 AM

View PostSteamyTea, on 15 April 2016 - 09:52 AM, said:

I thought raising CO2 levels reduced hyperventilation, why people that have panic attacks breath in from a paper bag.
http://www.healthlin...yperventilation
There was a bit in my comic a while back about using CO2 for medical purposes, can't remember what now though.

Thus my comment above about ensuring blood levels don't get too low either: what room air CO2 concentrations are good/bad in either direction?

Rgds

Damon

#15 joiner

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Posted 15 April 2016 - 11:36 AM

In layman's terms then, it's pretty sneaky stuff. :rolleyes:

#16 joiner

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Posted 15 April 2016 - 11:51 AM

Instant chord struck when I read this.

Yesterday afternoon I called into one of the council offices and within seconds felt compelled to comment on the "quality" of the air in there. The only occupant said that "it must be the weather" and that she really ought to get the finances she wanted to get finished that afternoon done, but that she "couldn't get herself motivated". I suggested she open a window.

It's a 1960's building, "advanced" for its time but built more with design in mind than engineered as a place in which people would be expected to work and actually think whilst they were doing it. (And no cracks please about council workers thinking being an oxymoron). Metal framed (though 2g) windows that do allow 'night vent' opening but as top-hungs that create a draught at waist height, not top venitilation to take out the stale warm air at ceiling height via a circulating air current.

I'll send that link to the powers-that-be, not that anything will come of it.

#17 jsharris

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Posted 15 April 2016 - 12:36 PM

It's a relatively new issue in buildings, dating around the time that we started sealing up buildings to better control the temperature. I believe it was first noticed in office buildings, where it has become normal to design completely sealed buildings without opening windows and then provide suitable ventilation. I know of one such building where, because of government policy at the time, the architect and engineers design was accepted, but with the stipulation that the air handling system had to be removed, as it was government policy to not fit "air conditioning" to public buildings. The building was built and within weeks people started feeling unwell. The cause was due to high CO2 and RH levels inside the building. It had to be retrofitted with a proper air handling and ventilation system before it was safe to use.

Part of my last job included building a new building to house 40 labs and 900 staff. It was airtight, with no opening windows, and although the labs had forced air ventilation the office areas relied on natural convection. There were two louvred "chimneys" with heat recovery rotating drum heat exchangers above internal atria that extended up from ground level to one level above top floor level. These provided the air exit route, with warmed air rising and exiting via the rotating drum heat exchangers, with the louvres being adjusted automatically to control the flow rate (and provide an emergency means of letting smoke out in the event of a fire).

Fresh air was drawn in through the roof top air handling system (passively, with no fans) and passed through the other side of the rotating drum heat exchanger before being distributed though the office areas by ceiling ducts.

What was impressive was the power of the "stack effect" in these atria. When the fire alarm operated sliding doors at ground level opened as fire escapes, along with all the louvres at the top of the atria. The first test we did we got the door opening timing wrong and the roof vents opened before the sliding doors. The suction lifted the sliding doors off their tracks, with the doors being sucked into the offices, with the base probably 18" in from the frame. If I hadn't seen it I'd have never believed that natural convection could be so powerful.

We're now beginning to see problems in homes because of all the efforts made in recent years to reduce heat loss by decreasing draughts. I've shown here before how ineffective leaving a window open is, and trickle vents are almost certainly even poorer at providing good ventilation. A good indicator of how bad some houses are is that many people notice the air quality in a house fitted with MVHR straight away. It was one of the first things my wife noticed on the first passive house we visited. We should pay more attention to ensuring houses are energy efficient, but also well ventilated. Currently I do not think that our building regulations are even half way adequate, as you can build a fairly airtight house with just window trickle vents as ventilation, plus a couple of intermittent extractor fans. I bet we see more cases of people feeling unwell in new houses before long, as very few developers fit proper ventilation systems.

#18 JmS

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Posted 16 April 2016 - 08:42 AM

This is the reason I'm considering single room hrv as we are doing more work to stop draughts. I fully understand a whole house system is pointless for us as we won't be anywhere near the airtight levels but I want to bring in fresh air in a controlled way and get stale moist air out. The current draughts do not allow for this so some sort of forced ventilation is needed I feel

#19 joiner

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Posted 16 April 2016 - 09:07 AM

JmS - Be careful because it could actually increase the draughts unless the air exchange is balanced.

Anyone care to address whether that is likely to be a potential problem and if yes what would need to be done to avoid it?

Edited by joiner, 16 April 2016 - 09:08 AM.


#20 jsharris

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Posted 16 April 2016 - 09:13 AM

The single room units are balanced, so allow fresh air in at the same rate as stale air is exhausted. At background ventilation rates there is no significant risk of draughts. I've seen what is now the FreshR unit and the flow rate is modest, and the unit almost totally inaudible.