How much natural airflow do you need in a room to not die of CO2 poisoning?

Factual Questions
1

Two questions:

  1. If you placed a human being in a hermetically sealed room that was say, 3m x 3m x 3m (or 10ft x 10ft x 10ft if you are into imperial), how long could they survive before succumbing to CO2 poisoning (assume all of their other needs are taken care of)? Is it on the order of hours/days/weeks/months/years?

  2. How much natural airflow would you need to allow into that room before a human being could survive in there indefinitely? Is the crack at the bottom of the door sufficient? Or a slightly ajar window?

The reason I ask is because, as building technology becomes more advanced, we’re increasingly creating more airtight spaces for energy/air quality reasons. With traditional building techniques, the inherent imprecision of the materials allowed for some degree of draftiness but modern materials allow for completely airtight seals. I’m wondering if this is something builders actually need to consider and whether improperly built spaces that are too well sealed off could end up being dangerous or is this such a minor concern that it would never actually come up in practice?

2

I don’t have the numbers from the standards at hand at the moment, so I can’t answer your first two questions directly, but it is absolutely a building code requirement in many countries that the building and/or HVAC systems be designed to provide sufficient airflow to maintain a viable atmosphere inside for occupants. Relying on building leakage alone is insufficient to meet codes in countries that I am familiar with.

In Australia, the room can be provided with openable windows and/or doors of at least 5% of the floor area to meet this requirement or you can supply outside air with a fan of at least 10L/s per person. Most of the airflow volume of the fan option is for odour and particulate control, but I recall reading somewhere (no cite) that for oxygen provision something on the order of 2L/s person of outside air is plenty. This is for typical buildings and presumably has a big safety factor built in to account for atmospheric pollutants, etc.

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3

Back of envelope calculations:

In a 3m cubic sealed room there are 27M3 of air 78% N, 21 % O2, 0% CO2, 1% other gases.
You take 15 breaths of 500ml every minute and the expired air is 17% O2, 4% CO2 others being constant.
Hence you are replacing 300ml of O2 with CO2 every minute. But at the start of the process there are 5.6bill ml O2 in the room.

After 100,000 minutes (approx 70 days) the concentration of C02 would have risen to 0.1111% which is just over 1,000 ppm.

Signs of CO2 intoxication have been produced by a 30-minute exposure at 50,000 ppm and a few minutes exposure at 70,000 to 100,000 ppm produces unconsciousness.
Am sure somebody can tell me have many factors of 10 I’m out. :slight_smile: